Commit e9a83bd2 authored by Linus Torvalds's avatar Linus Torvalds

Merge tag 'docs-5.3' of git://git.lwn.net/linux

Pull Documentation updates from Jonathan Corbet:
 "It's been a relatively busy cycle for docs:

   - A fair pile of RST conversions, many from Mauro. These create more
     than the usual number of simple but annoying merge conflicts with
     other trees, unfortunately. He has a lot more of these waiting on
     the wings that, I think, will go to you directly later on.

   - A new document on how to use merges and rebases in kernel repos,
     and one on Spectre vulnerabilities.

   - Various improvements to the build system, including automatic
     markup of function() references because some people, for reasons I
     will never understand, were of the opinion that
     :c:func:``function()`` is unattractive and not fun to type.

   - We now recommend using sphinx 1.7, but still support back to 1.4.

   - Lots of smaller improvements, warning fixes, typo fixes, etc"

* tag 'docs-5.3' of git://git.lwn.net/linux: (129 commits)
  docs: automarkup.py: ignore exceptions when seeking for xrefs
  docs: Move binderfs to admin-guide
  Disable Sphinx SmartyPants in HTML output
  doc: RCU callback locks need only _bh, not necessarily _irq
  docs: format kernel-parameters -- as code
  Doc : doc-guide : Fix a typo
  platform: x86: get rid of a non-existent document
  Add the RCU docs to the core-api manual
  Documentation: RCU: Add TOC tree hooks
  Documentation: RCU: Rename txt files to rst
  Documentation: RCU: Convert RCU UP systems to reST
  Documentation: RCU: Convert RCU linked list to reST
  Documentation: RCU: Convert RCU basic concepts to reST
  docs: filesystems: Remove uneeded .rst extension on toctables
  scripts/sphinx-pre-install: fix out-of-tree build
  docs: zh_CN: submitting-drivers.rst: Remove a duplicated Documentation/
  Documentation: PGP: update for newer HW devices
  Documentation: Add section about CPU vulnerabilities for Spectre
  Documentation: platform: Delete x86-laptop-drivers.txt
  docs: Note that :c:func: should no longer be used
  ...
parents 7011b7e1 454f96f2
......@@ -137,7 +137,8 @@ Description: Discover cpuidle policy and mechanism
current_governor: (RW) displays current idle policy. Users can
switch the governor at runtime by writing to this file.
See files in Documentation/cpuidle/ for more information.
See Documentation/admin-guide/pm/cpuidle.rst and
Documentation/driver-api/pm/cpuidle.rst for more information.
What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/name
......
......@@ -11,4 +11,4 @@ Description:
example would be, if User A has shares = 1024 and user
B has shares = 2048, User B will get twice the CPU
bandwidth user A will. For more details refer
Documentation/scheduler/sched-design-CFS.txt
Documentation/scheduler/sched-design-CFS.rst
......@@ -198,7 +198,7 @@ call to set the mask to the value returned.
::
size_t
dma_direct_max_mapping_size(struct device *dev);
dma_max_mapping_size(struct device *dev);
Returns the maximum size of a mapping for the device. The size parameter
of the mapping functions like dma_map_single(), dma_map_page() and
......
:orphan:
====
EDID
====
In the good old days when graphics parameters were configured explicitly
in a file called xorg.conf, even broken hardware could be managed.
......@@ -34,16 +40,19 @@ Makefile. Please note that the EDID data structure expects the timing
values in a different way as compared to the standard X11 format.
X11:
HTimings: hdisp hsyncstart hsyncend htotal
VTimings: vdisp vsyncstart vsyncend vtotal
EDID:
#define XPIX hdisp
#define XBLANK htotal-hdisp
#define XOFFSET hsyncstart-hdisp
#define XPULSE hsyncend-hsyncstart
#define YPIX vdisp
#define YBLANK vtotal-vdisp
#define YOFFSET vsyncstart-vdisp
#define YPULSE vsyncend-vsyncstart
HTimings:
hdisp hsyncstart hsyncend htotal
VTimings:
vdisp vsyncstart vsyncend vtotal
EDID::
#define XPIX hdisp
#define XBLANK htotal-hdisp
#define XOFFSET hsyncstart-hdisp
#define XPULSE hsyncend-hsyncstart
#define YPIX vdisp
#define YBLANK vtotal-vdisp
#define YOFFSET vsyncstart-vdisp
#define YPULSE vsyncend-vsyncstart
config WARN_MISSING_DOCUMENTS
bool "Warn if there's a missing documentation file"
depends on COMPILE_TEST
help
It is not uncommon that a document gets renamed.
This option makes the Kernel to check for missing dependencies,
warning when something is missing. Works only if the Kernel
is built from a git tree.
If unsure, select 'N'.
......@@ -4,6 +4,11 @@
subdir-y := devicetree/bindings/
# Check for broken documentation file references
ifeq ($(CONFIG_WARN_MISSING_DOCUMENTS),y)
$(shell $(srctree)/scripts/documentation-file-ref-check --warn)
endif
# You can set these variables from the command line.
SPHINXBUILD = sphinx-build
SPHINXOPTS =
......@@ -23,11 +28,13 @@ ifeq ($(HAVE_SPHINX),0)
.DEFAULT:
$(warning The '$(SPHINXBUILD)' command was not found. Make sure you have Sphinx installed and in PATH, or set the SPHINXBUILD make variable to point to the full path of the '$(SPHINXBUILD)' executable.)
@echo
@./scripts/sphinx-pre-install
@$(srctree)/scripts/sphinx-pre-install
@echo " SKIP Sphinx $@ target."
else # HAVE_SPHINX
export SPHINXOPTS = $(shell perl -e 'open IN,"sphinx-build --version 2>&1 |"; while (<IN>) { if (m/([\d\.]+)/) { print "-jauto" if ($$1 >= "1.7") } ;} close IN')
# User-friendly check for pdflatex and latexmk
HAVE_PDFLATEX := $(shell if which $(PDFLATEX) >/dev/null 2>&1; then echo 1; else echo 0; fi)
HAVE_LATEXMK := $(shell if which latexmk >/dev/null 2>&1; then echo 1; else echo 0; fi)
......@@ -70,12 +77,14 @@ quiet_cmd_sphinx = SPHINX $@ --> file://$(abspath $(BUILDDIR)/$3/$4)
$(abspath $(BUILDDIR)/$3/$4)
htmldocs:
@$(srctree)/scripts/sphinx-pre-install --version-check
@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,html,$(var),,$(var)))
linkcheckdocs:
@$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,linkcheck,$(var),,$(var)))
latexdocs:
@$(srctree)/scripts/sphinx-pre-install --version-check
@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,latex,$(var),latex,$(var)))
ifeq ($(HAVE_PDFLATEX),0)
......@@ -87,14 +96,17 @@ pdfdocs:
else # HAVE_PDFLATEX
pdfdocs: latexdocs
@$(srctree)/scripts/sphinx-pre-install --version-check
$(foreach var,$(SPHINXDIRS), $(MAKE) PDFLATEX="$(PDFLATEX)" LATEXOPTS="$(LATEXOPTS)" -C $(BUILDDIR)/$(var)/latex || exit;)
endif # HAVE_PDFLATEX
epubdocs:
@$(srctree)/scripts/sphinx-pre-install --version-check
@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,epub,$(var),epub,$(var)))
xmldocs:
@$(srctree)/scripts/sphinx-pre-install --version-check
@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,xml,$(var),xml,$(var)))
endif # HAVE_SPHINX
......
RCU on Uniprocessor Systems
.. _up_doc:
RCU on Uniprocessor Systems
===========================
A common misconception is that, on UP systems, the call_rcu() primitive
may immediately invoke its function. The basis of this misconception
is that since there is only one CPU, it should not be necessary to
wait for anything else to get done, since there are no other CPUs for
anything else to be happening on. Although this approach will -sort- -of-
anything else to be happening on. Although this approach will *sort of*
work a surprising amount of the time, it is a very bad idea in general.
This document presents three examples that demonstrate exactly how bad
an idea this is.
Example 1: softirq Suicide
--------------------------
Suppose that an RCU-based algorithm scans a linked list containing
elements A, B, and C in process context, and can delete elements from
......@@ -28,8 +30,8 @@ your kernel.
This same problem can occur if call_rcu() is invoked from a hardware
interrupt handler.
Example 2: Function-Call Fatality
---------------------------------
Of course, one could avert the suicide described in the preceding example
by having call_rcu() directly invoke its arguments only if it was called
......@@ -46,11 +48,13 @@ its arguments would cause it to fail to make the fundamental guarantee
underlying RCU, namely that call_rcu() defers invoking its arguments until
all RCU read-side critical sections currently executing have completed.
Quick Quiz #1: why is it -not- legal to invoke synchronize_rcu() in
this case?
Quick Quiz #1:
Why is it *not* legal to invoke synchronize_rcu() in this case?
:ref:`Answers to Quick Quiz <answer_quick_quiz_up>`
Example 3: Death by Deadlock
----------------------------
Suppose that call_rcu() is invoked while holding a lock, and that the
callback function must acquire this same lock. In this case, if
......@@ -76,25 +80,30 @@ there are cases where this can be quite ugly:
If call_rcu() directly invokes the callback, painful locking restrictions
or API changes would be required.
Quick Quiz #2: What locking restriction must RCU callbacks respect?
Quick Quiz #2:
What locking restriction must RCU callbacks respect?
:ref:`Answers to Quick Quiz <answer_quick_quiz_up>`
Summary
-------
Permitting call_rcu() to immediately invoke its arguments breaks RCU,
even on a UP system. So do not do it! Even on a UP system, the RCU
infrastructure -must- respect grace periods, and -must- invoke callbacks
infrastructure *must* respect grace periods, and *must* invoke callbacks
from a known environment in which no locks are held.
Note that it -is- safe for synchronize_rcu() to return immediately on
UP systems, including !PREEMPT SMP builds running on UP systems.
Note that it *is* safe for synchronize_rcu() to return immediately on
UP systems, including PREEMPT SMP builds running on UP systems.
Quick Quiz #3: Why can't synchronize_rcu() return immediately on
UP systems running preemptable RCU?
Quick Quiz #3:
Why can't synchronize_rcu() return immediately on UP systems running
preemptable RCU?
.. _answer_quick_quiz_up:
Answer to Quick Quiz #1:
Why is it -not- legal to invoke synchronize_rcu() in this case?
Why is it *not* legal to invoke synchronize_rcu() in this case?
Because the calling function is scanning an RCU-protected linked
list, and is therefore within an RCU read-side critical section.
......@@ -104,12 +113,13 @@ Answer to Quick Quiz #1:
Answer to Quick Quiz #2:
What locking restriction must RCU callbacks respect?
Any lock that is acquired within an RCU callback must be
acquired elsewhere using an _irq variant of the spinlock
primitive. For example, if "mylock" is acquired by an
RCU callback, then a process-context acquisition of this
lock must use something like spin_lock_irqsave() to
acquire the lock.
Any lock that is acquired within an RCU callback must be acquired
elsewhere using an _bh variant of the spinlock primitive.
For example, if "mylock" is acquired by an RCU callback, then
a process-context acquisition of this lock must use something
like spin_lock_bh() to acquire the lock. Please note that
it is also OK to use _irq variants of spinlocks, for example,
spin_lock_irqsave().
If the process-context code were to simply use spin_lock(),
then, since RCU callbacks can be invoked from softirq context,
......@@ -119,7 +129,7 @@ Answer to Quick Quiz #2:
This restriction might seem gratuitous, since very few RCU
callbacks acquire locks directly. However, a great many RCU
callbacks do acquire locks -indirectly-, for example, via
callbacks do acquire locks *indirectly*, for example, via
the kfree() primitive.
Answer to Quick Quiz #3:
......
.. _rcu_concepts:
============
RCU concepts
============
.. toctree::
:maxdepth: 1
rcu
listRCU
UP
.. only:: subproject and html
Indices
=======
* :ref:`genindex`
Using RCU to Protect Read-Mostly Linked Lists
.. _list_rcu_doc:
Using RCU to Protect Read-Mostly Linked Lists
=============================================
One of the best applications of RCU is to protect read-mostly linked lists
("struct list_head" in list.h). One big advantage of this approach
......@@ -7,8 +9,8 @@ is that all of the required memory barriers are included for you in
the list macros. This document describes several applications of RCU,
with the best fits first.
Example 1: Read-Side Action Taken Outside of Lock, No In-Place Updates
----------------------------------------------------------------------
The best applications are cases where, if reader-writer locking were
used, the read-side lock would be dropped before taking any action
......@@ -24,7 +26,7 @@ added or deleted, rather than being modified in place.
A straightforward example of this use of RCU may be found in the
system-call auditing support. For example, a reader-writer locked
implementation of audit_filter_task() might be as follows:
implementation of audit_filter_task() might be as follows::
static enum audit_state audit_filter_task(struct task_struct *tsk)
{
......@@ -48,7 +50,7 @@ the corresponding value is returned. By the time that this value is acted
on, the list may well have been modified. This makes sense, since if
you are turning auditing off, it is OK to audit a few extra system calls.
This means that RCU can be easily applied to the read side, as follows:
This means that RCU can be easily applied to the read side, as follows::
static enum audit_state audit_filter_task(struct task_struct *tsk)
{
......@@ -73,7 +75,7 @@ become list_for_each_entry_rcu(). The _rcu() list-traversal primitives
insert the read-side memory barriers that are required on DEC Alpha CPUs.
The changes to the update side are also straightforward. A reader-writer
lock might be used as follows for deletion and insertion:
lock might be used as follows for deletion and insertion::
static inline int audit_del_rule(struct audit_rule *rule,
struct list_head *list)
......@@ -106,7 +108,7 @@ lock might be used as follows for deletion and insertion:
return 0;
}
Following are the RCU equivalents for these two functions:
Following are the RCU equivalents for these two functions::
static inline int audit_del_rule(struct audit_rule *rule,
struct list_head *list)
......@@ -154,13 +156,13 @@ otherwise cause concurrent readers to fail spectacularly.
So, when readers can tolerate stale data and when entries are either added
or deleted, without in-place modification, it is very easy to use RCU!
Example 2: Handling In-Place Updates
------------------------------------
The system-call auditing code does not update auditing rules in place.
However, if it did, reader-writer-locked code to do so might look as
follows (presumably, the field_count is only permitted to decrease,
otherwise, the added fields would need to be filled in):
otherwise, the added fields would need to be filled in)::
static inline int audit_upd_rule(struct audit_rule *rule,
struct list_head *list,
......@@ -187,7 +189,7 @@ otherwise, the added fields would need to be filled in):
The RCU version creates a copy, updates the copy, then replaces the old
entry with the newly updated entry. This sequence of actions, allowing
concurrent reads while doing a copy to perform an update, is what gives
RCU ("read-copy update") its name. The RCU code is as follows:
RCU ("read-copy update") its name. The RCU code is as follows::
static inline int audit_upd_rule(struct audit_rule *rule,
struct list_head *list,
......@@ -216,8 +218,8 @@ RCU ("read-copy update") its name. The RCU code is as follows:
Again, this assumes that the caller holds audit_netlink_sem. Normally,
the reader-writer lock would become a spinlock in this sort of code.
Example 3: Eliminating Stale Data
---------------------------------
The auditing examples above tolerate stale data, as do most algorithms
that are tracking external state. Because there is a delay from the
......@@ -231,13 +233,16 @@ per-entry spinlock, and, if the "deleted" flag is set, pretends that the
entry does not exist. For this to be helpful, the search function must
return holding the per-entry spinlock, as ipc_lock() does in fact do.
Quick Quiz: Why does the search function need to return holding the
per-entry lock for this deleted-flag technique to be helpful?
Quick Quiz:
Why does the search function need to return holding the per-entry lock for
this deleted-flag technique to be helpful?
:ref:`Answer to Quick Quiz <answer_quick_quiz_list>`
If the system-call audit module were to ever need to reject stale data,
one way to accomplish this would be to add a "deleted" flag and a "lock"
spinlock to the audit_entry structure, and modify audit_filter_task()
as follows:
as follows::
static enum audit_state audit_filter_task(struct task_struct *tsk)
{
......@@ -268,7 +273,7 @@ audit_upd_rule() would need additional memory barriers to ensure
that the list_add_rcu() was really executed before the list_del_rcu().
The audit_del_rule() function would need to set the "deleted"
flag under the spinlock as follows:
flag under the spinlock as follows::
static inline int audit_del_rule(struct audit_rule *rule,
struct list_head *list)
......@@ -290,8 +295,8 @@ flag under the spinlock as follows:
return -EFAULT; /* No matching rule */
}
Summary
-------
Read-mostly list-based data structures that can tolerate stale data are
the most amenable to use of RCU. The simplest case is where entries are
......@@ -302,8 +307,9 @@ If stale data cannot be tolerated, then a "deleted" flag may be used
in conjunction with a per-entry spinlock in order to allow the search
function to reject newly deleted data.
.. _answer_quick_quiz_list:
Answer to Quick Quiz
Answer to Quick Quiz:
Why does the search function need to return holding the per-entry
lock for this deleted-flag technique to be helpful?
......
.. _rcu_doc:
RCU Concepts
============
The basic idea behind RCU (read-copy update) is to split destructive
operations into two parts, one that prevents anyone from seeing the data
item being destroyed, and one that actually carries out the destruction.
A "grace period" must elapse between the two parts, and this grace period
must be long enough that any readers accessing the item being deleted have
since dropped their references. For example, an RCU-protected deletion
from a linked list would first remove the item from the list, wait for
a grace period to elapse, then free the element. See the
Documentation/RCU/listRCU.rst file for more information on using RCU with
linked lists.
Frequently Asked Questions
--------------------------
- Why would anyone want to use RCU?
The advantage of RCU's two-part approach is that RCU readers need
not acquire any locks, perform any atomic instructions, write to
shared memory, or (on CPUs other than Alpha) execute any memory
barriers. The fact that these operations are quite expensive
on modern CPUs is what gives RCU its performance advantages
in read-mostly situations. The fact that RCU readers need not
acquire locks can also greatly simplify deadlock-avoidance code.
- How can the updater tell when a grace period has completed
if the RCU readers give no indication when they are done?
Just as with spinlocks, RCU readers are not permitted to
block, switch to user-mode execution, or enter the idle loop.
Therefore, as soon as a CPU is seen passing through any of these
three states, we know that that CPU has exited any previous RCU
read-side critical sections. So, if we remove an item from a
linked list, and then wait until all CPUs have switched context,
executed in user mode, or executed in the idle loop, we can
safely free up that item.
Preemptible variants of RCU (CONFIG_PREEMPT_RCU) get the
same effect, but require that the readers manipulate CPU-local
counters. These counters allow limited types of blocking within
RCU read-side critical sections. SRCU also uses CPU-local
counters, and permits general blocking within RCU read-side
critical sections. These variants of RCU detect grace periods
by sampling these counters.
- If I am running on a uniprocessor kernel, which can only do one
thing at a time, why should I wait for a grace period?
See the Documentation/RCU/UP.rst file for more information.
- How can I see where RCU is currently used in the Linux kernel?
Search for "rcu_read_lock", "rcu_read_unlock", "call_rcu",
"rcu_read_lock_bh", "rcu_read_unlock_bh", "srcu_read_lock",
"srcu_read_unlock", "synchronize_rcu", "synchronize_net",
"synchronize_srcu", and the other RCU primitives. Or grab one
of the cscope databases from:
(http://www.rdrop.com/users/paulmck/RCU/linuxusage/rculocktab.html).
- What guidelines should I follow when writing code that uses RCU?
See the checklist.txt file in this directory.
- Why the name "RCU"?
"RCU" stands for "read-copy update". The file Documentation/RCU/listRCU.rst
has more information on where this name came from, search for
"read-copy update" to find it.
- I hear that RCU is patented? What is with that?
Yes, it is. There are several known patents related to RCU,
search for the string "Patent" in RTFP.txt to find them.
Of these, one was allowed to lapse by the assignee, and the
others have been contributed to the Linux kernel under GPL.
There are now also LGPL implementations of user-level RCU
available (http://liburcu.org/).
- I hear that RCU needs work in order to support realtime kernels?
Realtime-friendly RCU can be enabled via the CONFIG_PREEMPT_RCU
kernel configuration parameter.
- Where can I find more information on RCU?
See the RTFP.txt file in this directory.
Or point your browser at (http://www.rdrop.com/users/paulmck/RCU/).
RCU Concepts
The basic idea behind RCU (read-copy update) is to split destructive
operations into two parts, one that prevents anyone from seeing the data
item being destroyed, and one that actually carries out the destruction.
A "grace period" must elapse between the two parts, and this grace period
must be long enough that any readers accessing the item being deleted have
since dropped their references. For example, an RCU-protected deletion
from a linked list would first remove the item from the list, wait for
a grace period to elapse, then free the element. See the listRCU.txt
file for more information on using RCU with linked lists.
Frequently Asked Questions
o Why would anyone want to use RCU?
The advantage of RCU's two-part approach is that RCU readers need
not acquire any locks, perform any atomic instructions, write to
shared memory, or (on CPUs other than Alpha) execute any memory
barriers. The fact that these operations are quite expensive
on modern CPUs is what gives RCU its performance advantages
in read-mostly situations. The fact that RCU readers need not
acquire locks can also greatly simplify deadlock-avoidance code.
o How can the updater tell when a grace period has completed
if the RCU readers give no indication when they are done?
Just as with spinlocks, RCU readers are not permitted to
block, switch to user-mode execution, or enter the idle loop.
Therefore, as soon as a CPU is seen passing through any of these
three states, we know that that CPU has exited any previous RCU
read-side critical sections. So, if we remove an item from a
linked list, and then wait until all CPUs have switched context,
executed in user mode, or executed in the idle loop, we can
safely free up that item.
Preemptible variants of RCU (CONFIG_PREEMPT_RCU) get the
same effect, but require that the readers manipulate CPU-local
counters. These counters allow limited types of blocking within
RCU read-side critical sections. SRCU also uses CPU-local
counters, and permits general blocking within RCU read-side
critical sections. These variants of RCU detect grace periods
by sampling these counters.
o If I am running on a uniprocessor kernel, which can only do one
thing at a time, why should I wait for a grace period?
See the UP.txt file in this directory.
o How can I see where RCU is currently used in the Linux kernel?
Search for "rcu_read_lock", "rcu_read_unlock", "call_rcu",
"rcu_read_lock_bh", "rcu_read_unlock_bh", "srcu_read_lock",
"srcu_read_unlock", "synchronize_rcu", "synchronize_net",
"synchronize_srcu", and the other RCU primitives. Or grab one
of the cscope databases from:
http://www.rdrop.com/users/paulmck/RCU/linuxusage/rculocktab.html
o What guidelines should I follow when writing code that uses RCU?
See the checklist.txt file in this directory.
o Why the name "RCU"?
"RCU" stands for "read-copy update". The file listRCU.txt has
more information on where this name came from, search for
"read-copy update" to find it.
o I hear that RCU is patented? What is with that?
Yes, it is. There are several known patents related to RCU,
search for the string "Patent" in RTFP.txt to find them.
Of these, one was allowed to lapse by the assignee, and the
others have been contributed to the Linux kernel under GPL.
There are now also LGPL implementations of user-level RCU
available (http://liburcu.org/).
o I hear that RCU needs work in order to support realtime kernels?
Realtime-friendly RCU can be enabled via the CONFIG_PREEMPT_RCU
kernel configuration parameter.
o Where can I find more information on RCU?
See the RTFP.txt file in this directory.
Or point your browser at http://www.rdrop.com/users/paulmck/RCU/.
:orphan:
========================================================
OpenCAPI (Open Coherent Accelerator Processor Interface)
========================================================
......
......@@ -96,4 +96,4 @@ where
<URL:http://www.uefi.org/sites/default/files/resources/_DSD-hierarchical-data-extension-UUID-v1.1.pdf>,
referenced 2019-02-21.
[7] Documentation/acpi/dsd/data-node-reference.txt
[7] Documentation/firmware-guide/acpi/dsd/data-node-references.rst
......@@ -227,7 +227,7 @@ Configuring the kernel
"make tinyconfig" Configure the tiniest possible kernel.
You can find more information on using the Linux kernel config tools
in Documentation/kbuild/kconfig.txt.
in Documentation/kbuild/kconfig.rst.
- NOTES on ``make config``:
......
......@@ -90,7 +90,7 @@ the disk is not available then you have three options:
run a null modem to a second machine and capture the output there
using your favourite communication program. Minicom works well.
(3) Use Kdump (see Documentation/kdump/kdump.txt),
(3) Use Kdump (see Documentation/kdump/kdump.rst),
extract the kernel ring buffer from old memory with using dmesg
gdbmacro in Documentation/kdump/gdbmacros.txt.
......
......@@ -9,5 +9,6 @@ are configurable at compile, boot or run time.
.. toctree::
:maxdepth: 1
spectre
l1tf
mds
This diff is collapsed.
......@@ -70,6 +70,7 @@ configure specific aspects of kernel behavior to your liking.
ras
bcache
ext4
binderfs
pm/index
thunderbolt
LSM/index
......
......@@ -9,11 +9,11 @@ and sorted into English Dictionary order (defined as ignoring all
punctuation and sorting digits before letters in a case insensitive
manner), and with descriptions where known.
The kernel parses parameters from the kernel command line up to "--";
The kernel parses parameters from the kernel command line up to "``--``";
if it doesn't recognize a parameter and it doesn't contain a '.', the
parameter gets passed to init: parameters with '=' go into init's
environment, others are passed as command line arguments to init.
Everything after "--" is passed as an argument to init.
Everything after "``--``" is passed as an argument to init.
Module parameters can be specified in two ways: via the kernel command
line with a module name prefix, or via modprobe, e.g.::
......@@ -167,7 +167,7 @@ parameter is applicable::
X86-32 X86-32, aka i386 architecture is enabled.
X86-64 X86-64 architecture is enabled.
More X86-64 boot options can be found in
Documentation/x86/x86_64/boot-options.txt .
Documentation/x86/x86_64/boot-options.rst.
X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
X86_UV SGI UV support is enabled.
XEN Xen support is enabled
......@@ -181,10 +181,10 @@ In addition, the following text indicates that the option::
Parameters denoted with BOOT are actually interpreted by the boot
loader, and have no meaning to the kernel directly.
Do not modify the syntax of boot loader parameters without extreme
need or coordination with <Documentation/x86/boot.txt>.
need or coordination with <Documentation/x86/boot.rst>.
There are also arch-specific kernel-parameters not documented here.
See for example <Documentation/x86/x86_64/boot-options.txt>.
See for example <Documentation/x86/x86_64/boot-options.rst>.
Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
a trailing = on the name of any parameter states that that parameter will
......
......@@ -53,7 +53,7 @@
ACPI_DEBUG_PRINT statements, e.g.,
ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
The debug_level mask defaults to "info". See
Documentation/acpi/debug.txt for more information about
Documentation/firmware-guide/acpi/debug.rst for more information about
debug layers and levels.
Enable processor driver info messages:
......@@ -708,14 +708,14 @@
[KNL, x86_64] select a region under 4G first, and
fall back to reserve region above 4G when '@offset'
hasn't been specified.
See Documentation/kdump/kdump.txt for further details.
See Documentation/kdump/kdump.rst for further details.
crashkernel=range1:size1[,range2:size2,...][@offset]
[KNL] Same as above, but depends on the memory
in the running system. The syntax of range is
start-[end] where start and end are both
a memory unit (amount[KMG]). See also
Documentation/kdump/kdump.txt for an example.
Documentation/kdump/kdump.rst for an example.
crashkernel=size[KMG],high
[KNL, x86_64] range could be above 4G. Allow kernel
......@@ -932,7 +932,7 @@
edid/1680x1050.bin, or edid/1920x1080.bin is given
and no file with the same name exists. Details and
instructions how to build your own EDID data are
available in Documentation/EDID/HOWTO.txt. An EDID
available in Documentation/EDID/howto.rst. An EDID
data set will only be used for a particular connector,
if its name and a colon are prepended to the EDID
name. Each connector may use a unique EDID data
......@@ -963,7 +963,7 @@
for details.
nompx [X86] Disables Intel Memory Protection Extensions.
See Documentation/x86/intel_mpx.txt for more
See Documentation/x86/intel_mpx.rst for more
information about the feature.
nopku [X86] Disable Memory Protection Keys CPU feature found
......@@ -1189,7 +1189,7 @@
that is to be dynamically loaded by Linux. If there are
multiple variables with the same name but with different
vendor GUIDs, all of them will be loaded. See
Documentation/acpi/ssdt-overlays.txt for details.
Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
eisa_irq_edge= [PARISC,HW]
......@@ -1209,7 +1209,7 @@
Specifies physical address of start of kernel core
image elf header and optionally the size. Generally
kexec loader will pass this option to capture kernel.
See Documentation/kdump/kdump.txt for details.
See Documentation/kdump/kdump.rst for details.
enable_mtrr_cleanup [X86]
The kernel tries to adjust MTRR layout from continuous
......@@ -1388,9 +1388,6 @@
Valid parameters: "on", "off"
Default: "on"
hisax= [HW,ISDN]
See Documentation/isdn/README.HiSax.
hlt [BUGS=ARM,SH]
hpet= [X86-32,HPET] option to control HPET usage
......@@ -1507,7 +1504,7 @@
Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
.cdrom .chs .ignore_cable are additional options
See Documentation/ide/ide.txt.
See Documentation/ide/ide.rst.
ide-generic.probe-mask= [HW] (E)IDE subsystem
Format: <int>
......@@ -2383,7 +2380,7 @@
mce [X86-32] Machine Check Exception
mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst
md= [HW] RAID subsystems devices and level
See Documentation/admin-guide/md.rst.
......@@ -2439,7 +2436,7 @@
set according to the
CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
option.
See Documentation/memory-hotplug.txt.
See Documentation/admin-guide/mm/memory-hotplug.rst.
memmap=exactmap [KNL,X86] Enable setting of an exact
E820 memory map, as specified by the user.
......@@ -2528,7 +2525,7 @@
mem_encrypt=on: Activate SME
mem_encrypt=off: Do not activate SME
Refer to Documentation/x86/amd-memory-encryption.txt
Refer to Documentation/virtual/kvm/amd-memory-encryption.rst
for details on when memory encryption can be activated.
mem_sleep_default= [SUSPEND] Default system suspend mode:
......@@ -2836,8 +2833,9 @@
0 - turn hardlockup detector in nmi_watchdog off
1 - turn hardlockup detector in nmi_watchdog on
When panic is specified, panic when an NMI watchdog
timeout occurs (or 'nopanic' to override the opposite
default). To disable both hard and soft lockup detectors,
timeout occurs (or 'nopanic' to not panic on an NMI
watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
To disable both hard and soft lockup detectors,
please see 'nowatchdog'.
This is useful when you use a panic=... timeout and
need the box quickly up again.
......@@ -3528,7 +3526,7 @@
See Documentation/blockdev/paride.txt.
pirq= [SMP,APIC] Manual mp-table setup
See Documentation/x86/i386/IO-APIC.txt.
See Documentation/x86/i386/IO-APIC.rst.
plip= [PPT,NET] Parallel port network link
Format: { parport<nr> | timid | 0 }
......@@ -5032,7 +5030,7 @@
vector=percpu: enable percpu vector domain
video= [FB] Frame buffer configuration
See Documentation/fb/modedb.txt.
See Documentation/fb/modedb.rst.
video.brightness_switch_enabled= [0,1]
If set to 1, on receiving an ACPI notify event
......@@ -5060,7 +5058,7 @@
Can be used multiple times for multiple devices.
vga= [BOOT,X86-32] Select a particular video mode
See Documentation/x86/boot.txt and
See Documentation/x86/boot.rst and
Documentation/svga.txt.
Use vga=ask for menu.
This is actually a boot loader parameter; the value is
......@@ -5167,7 +5165,7 @@
Default: 3 = cyan.
watchdog timers [HW,WDT] For information on watchdog timers,
see Documentation/watchdog/watchdog-parameters.txt
see Documentation/watchdog/watchdog-parameters.rst
or other driver-specific files in the
Documentation/watchdog/ directory.
......
......@@ -165,5 +165,6 @@ write-through caching.
========
See Also
========
.. [1] https://www.uefi.org/sites/default/files/resources/ACPI_6_2.pdf
Section 5.2.27
[1] https://www.uefi.org/sites/default/files/resources/ACPI_6_2.pdf
- Section 5.2.27
......@@ -199,7 +199,7 @@ Architecture (MCA)\ [#f3]_.
mode).
.. [#f3] For more details about the Machine Check Architecture (MCA),
please read Documentation/x86/x86_64/machinecheck at the Kernel tree.
please read Documentation/x86/x86_64/machinecheck.rst at the Kernel tree.
EDAC - Error Detection And Correction
*************************************
......
Introduction
============
ATA over Ethernet is a network protocol that provides simple access to
block storage on the LAN.
......@@ -22,7 +25,8 @@ document the use of the driver and are not necessary if you install
the aoetools.
CREATING DEVICE NODES
Creating Device Nodes
=====================
Users of udev should find the block device nodes created
automatically, but to create all the necessary device nodes, use the
......@@ -38,7 +42,8 @@ CREATING DEVICE NODES
confusing when an AoE device is not present the first time the a
command is run but appears a second later.
USING DEVICE NODES
Using Device Nodes
==================
"cat /dev/etherd/err" blocks, waiting for error diagnostic output,
like any retransmitted packets.
......@@ -55,7 +60,7 @@ USING DEVICE NODES
by sysfs counterparts. Using the commands in aoetools insulates
users from these implementation details.
The block devices are named like this:
The block devices are named like this::
e{shelf}.{slot}
e{shelf}.{slot}p{part}
......@@ -64,7 +69,8 @@ USING DEVICE NODES
first shelf (shelf address zero). That's the whole disk. The first
partition on that disk would be "e0.2p1".
USING SYSFS
Using sysfs
===========
Each aoe block device in /sys/block has the extra attributes of
state, mac, and netif. The state attribute is "up" when the device
......@@ -78,29 +84,29 @@ USING SYSFS
There is a script in this directory that formats this information in
a convenient way. Users with aoetools should use the aoe-stat
command.
root@makki root# sh Documentation/aoe/status.sh
e10.0 eth3 up
e10.1 eth3 up
e10.2 eth3 up
e10.3 eth3 up
e10.4 eth3 up
e10.5 eth3 up
e10.6 eth3 up
e10.7 eth3 up
e10.8 eth3 up
e10.9 eth3 up
e4.0 eth1 up
e4.1 eth1 up
e4.2 eth1 up
e4.3 eth1 up
e4.4 eth1 up
e4.5 eth1 up
e4.6 eth1 up
e4.7 eth1 up
e4.8 eth1 up
e4.9 eth1 up
command::
root@makki root# sh Documentation/aoe/status.sh
e10.0 eth3 up
e10.1 eth3 up
e10.2 eth3 up
e10.3 eth3 up
e10.4 eth3 up
e10.5 eth3 up
e10.6 eth3 up
e10.7 eth3 up
e10.8 eth3 up
e10.9 eth3 up
e4.0 eth1 up
e4.1 eth1 up
e4.2 eth1 up
e4.3 eth1 up
e4.4 eth1 up
e4.5 eth1 up
e4.6 eth1 up
e4.7 eth1 up
e4.8 eth1 up
e4.9 eth1 up
Use /sys/module/aoe/parameters/aoe_iflist (or better, the driver
option discussed below) instead of /dev/etherd/interfaces to limit
......@@ -113,12 +119,13 @@ USING SYSFS
for this purpose. You can also directly use the
/dev/etherd/discover special file described above.
DRIVER OPTIONS
Driver Options
==============
There is a boot option for the built-in aoe driver and a
corresponding module parameter, aoe_iflist. Without this option,
all network interfaces may be used for ATA over Ethernet. Here is a
usage example for the module parameter.
usage example for the module parameter::
modprobe aoe_iflist="eth1 eth3"
......
Example of udev rules
---------------------
.. include:: udev.txt
:literal:
Example of udev install rules script
------------------------------------
.. literalinclude:: udev-install.sh
:language: shell
Example script to get status
----------------------------
.. literalinclude:: status.sh
:language: shell
Example of AoE autoload script
------------------------------
.. literalinclude:: autoload.sh
:language: shell
:orphan:
=======================
ATA over Ethernet (AoE)
=======================
.. toctree::
:maxdepth: 1
aoe
todo
examples
.. only:: subproject and html
Indices
=======
* :ref:`genindex`
TODO
====
There is a potential for deadlock when allocating a struct sk_buff for
data that needs to be written out to aoe storage. If the data is
being written from a dirty page in order to free that page, and if
......
......@@ -11,7 +11,7 @@
# udev_rules="/etc/udev/rules.d/"
# bash# ls /etc/udev/rules.d/
# 10-wacom.rules 50-udev.rules
# bash# cp /path/to/linux-2.6.xx/Documentation/aoe/udev.txt \
# bash# cp /path/to/linux/Documentation/aoe/udev.txt \
# /etc/udev/rules.d/60-aoe.rules
#
......
Too many problems poped up because of unnoticed misaligned memory access in
Too many problems popped up because of unnoticed misaligned memory access in
kernel code lately. Therefore the alignment fixup is now unconditionally
configured in for SA11x0 based targets. According to Alan Cox, this is a
bad idea to configure it out, but Russell King has some good reasons for
......
:orphan:
========================
STM32 ARM Linux Overview
========================
......
:orphan:
STM32F429 Overview
==================
......
:orphan:
STM32F746 Overview
==================
......
:orphan:
STM32F769 Overview
==================
......
:orphan:
STM32H743 Overview
==================
......
:orphan:
STM32MP157 Overview
===================
......
Booting AArch64 Linux
=====================
=====================
Booting AArch64 Linux
=====================
Author: Will Deacon <will.deacon@arm.com>
Date : 07 September 2012
This document is based on the ARM booting document by Russell King and
......@@ -12,7 +14,7 @@ The AArch64 exception model is made up of a number of exception levels
counterpart. EL2 is the hypervisor level and exists only in non-secure
mode. EL3 is the highest priority level and exists only in secure mode.
For the purposes of this document, we will use the term `boot loader'
For the purposes of this document, we will use the term `boot loader`
simply to define all software that executes on the CPU(s) before control
is passed to the Linux kernel. This may include secure monitor and
hypervisor code, or it may just be a handful of instructions for
......@@ -70,7 +72,7 @@ Image target is available instead.
Requirement: MANDATORY
The decompressed kernel image contains a 64-byte header as follows:
The decompressed kernel image contains a 64-byte header as follows::
u32 code0; /* Executable code */
u32 code1; /* Executable code */
......@@ -103,19 +105,26 @@ Header notes:
- The flags field (introduced in v3.17) is a little-endian 64-bit field
composed as follows:
Bit 0: Kernel endianness. 1 if BE, 0 if LE.
Bit 1-2: Kernel Page size.
0 - Unspecified.
1 - 4K
2 - 16K
3 - 64K
Bit 3: Kernel physical placement
0 - 2MB aligned base should be as close as possible
to the base of DRAM, since memory below it is not
accessible via the linear mapping
1 - 2MB aligned base may be anywhere in physical
memory
Bits 4-63: Reserved.
============= ===============================================================
Bit 0 Kernel endianness. 1 if BE, 0 if LE.
Bit 1-2 Kernel Page size.
* 0 - Unspecified.
* 1 - 4K
* 2 - 16K
* 3 - 64K
Bit 3 Kernel physical placement
0
2MB aligned base should be as close as possible
to the base of DRAM, since memory below it is not
accessible via the linear mapping
1
2MB aligned base may be anywhere in physical
memory
Bits 4-63 Reserved.
============= ===============================================================
- When image_size is zero, a bootloader should attempt to keep as much
memory as possible free for use by the kernel immediately after the
......@@ -147,19 +156,22 @@ Before jumping into the kernel, the following conditions must be met:
corrupted by bogus network packets or disk data. This will save
you many hours of debug.
- Primary CPU general-purpose register settings
x0 = physical address of device tree blob (dtb) in system RAM.
x1 = 0 (reserved for future use)
x2 = 0 (reserved for future use)
x3 = 0 (reserved for future use)
- Primary CPU general-purpose register settings:
- x0 = physical address of device tree blob (dtb) in system RAM.
- x1 = 0 (reserved for future use)
- x2 = 0 (reserved for future use)
- x3 = 0 (reserved for future use)
- CPU mode
All forms of interrupts must be masked in PSTATE.DAIF (Debug, SError,
IRQ and FIQ).
The CPU must be in either EL2 (RECOMMENDED in order to have access to
the virtualisation extensions) or non-secure EL1.
- Caches, MMUs
The MMU must be off.
Instruction cache may be on or off.
The address range corresponding to the loaded kernel image must be
......@@ -172,18 +184,21 @@ Before jumping into the kernel, the following conditions must be met:
operations (not recommended) must be configured and disabled.
- Architected timers
CNTFRQ must be programmed with the timer frequency and CNTVOFF must
be programmed with a consistent value on all CPUs. If entering the
kernel at EL1, CNTHCTL_EL2 must have EL1PCTEN (bit 0) set where
available.
- Coherency
All CPUs to be booted by the kernel must be part of the same coherency
domain on entry to the kernel. This may require IMPLEMENTATION DEFINED
initialisation to enable the receiving of maintenance operations on
each CPU.
- System registers
All writable architected system registers at the exception level where
the kernel image will be entered must be initialised by software at a
higher exception level to prevent execution in an UNKNOWN state.
......@@ -195,28 +210,40 @@ Before jumping into the kernel, the following conditions must be met:
For systems with a GICv3 interrupt controller to be used in v3 mode:
- If EL3 is present:
ICC_SRE_EL3.Enable (bit 3) must be initialiased to 0b1.
ICC_SRE_EL3.SRE (bit 0) must be initialised to 0b1.
- ICC_SRE_EL3.Enable (bit 3) must be initialiased to 0b1.
- ICC_SRE_EL3.SRE (bit 0) must be initialised to 0b1.
- If the kernel is entered at EL1:
ICC.SRE_EL2.Enable (bit 3) must be initialised to 0b1
ICC_SRE_EL2.SRE (bit 0) must be initialised to 0b1.
- ICC.SRE_EL2.Enable (bit 3) must be initialised to 0b1
- ICC_SRE_EL2.SRE (bit 0) must be initialised to 0b1.
- The DT or ACPI tables must describe a GICv3 interrupt controller.
For systems with a GICv3 interrupt controller to be used in
compatibility (v2) mode:
- If EL3 is present:
ICC_SRE_EL3.SRE (bit 0) must be initialised to 0b0.
ICC_SRE_EL3.SRE (bit 0) must be initialised to 0b0.
- If the kernel is entered at EL1:
ICC_SRE_EL2.SRE (bit 0) must be initialised to 0b0.
ICC_SRE_EL2.SRE (bit 0) must be initialised to 0b0.
- The DT or ACPI tables must describe a GICv2 interrupt controller.
For CPUs with pointer authentication functionality:
- If EL3 is present:
SCR_EL3.APK (bit 16) must be initialised to 0b1
SCR_EL3.API (bit 17) must be initialised to 0b1
- SCR_EL3.APK (bit 16) must be initialised to 0b1
- SCR_EL3.API (bit 17) must be initialised to 0b1
- If the kernel is entered at EL1:
HCR_EL2.APK (bit 40) must be initialised to 0b1
HCR_EL2.API (bit 41) must be initialised to 0b1
- HCR_EL2.APK (bit 40) must be initialised to 0b1
- HCR_EL2.API (bit 41) must be initialised to 0b1
The requirements described above for CPU mode, caches, MMUs, architected
timers, coherency and system registers apply to all CPUs. All CPUs must
......
================
ARM64 ELF hwcaps
================
......@@ -15,16 +16,16 @@ of flags called hwcaps, exposed in the auxilliary vector.
Userspace software can test for features by acquiring the AT_HWCAP or
AT_HWCAP2 entry of the auxiliary vector, and testing whether the relevant
flags are set, e.g.
flags are set, e.g.::
bool floating_point_is_present(void)
{
unsigned long hwcaps = getauxval(AT_HWCAP);
if (hwcaps & HWCAP_FP)
return true;
bool floating_point_is_present(void)
{
unsigned long hwcaps = getauxval(AT_HWCAP);
if (hwcaps & HWCAP_FP)
return true;
return false;
}
return false;
}
Where software relies on a feature described by a hwcap, it should check
the relevant hwcap flag to verify that the feature is present before
......@@ -45,7 +46,7 @@ userspace code at EL0. These hwcaps are defined in terms of ID register
fields, and should be interpreted with reference to the definition of
these fields in the ARM Architecture Reference Manual (ARM ARM).
Such hwcaps are described below in the form:
Such hwcaps are described below in the form::
Functionality implied by idreg.field == val.
......@@ -64,75 +65,58 @@ reference to ID registers, and may refer to other documentation.
---------------------------------
HWCAP_FP
Functionality implied by ID_AA64PFR0_EL1.FP == 0b0000.
HWCAP_ASIMD
Functionality implied by ID_AA64PFR0_EL1.AdvSIMD == 0b0000.
HWCAP_EVTSTRM
The generic timer is configured to generate events at a frequency of
approximately 100KHz.
HWCAP_AES
Functionality implied by ID_AA64ISAR0_EL1.AES == 0b0001.
HWCAP_PMULL
Functionality implied by ID_AA64ISAR0_EL1.AES == 0b0010.
HWCAP_SHA1
Functionality implied by ID_AA64ISAR0_EL1.SHA1 == 0b0001.
HWCAP_SHA2
Functionality implied by ID_AA64ISAR0_EL1.SHA2 == 0b0001.
HWCAP_CRC32
Functionality implied by ID_AA64ISAR0_EL1.CRC32 == 0b0001.
HWCAP_ATOMICS
Functionality implied by ID_AA64ISAR0_EL1.Atomic == 0b0010.
HWCAP_FPHP
Functionality implied by ID_AA64PFR0_EL1.FP == 0b0001.
HWCAP_ASIMDHP
Functionality implied by ID_AA64PFR0_EL1.AdvSIMD == 0b0001.
HWCAP_CPUID
EL0 access to certain ID registers is available, to the extent
described by Documentation/arm64/cpu-feature-registers.txt.
described by Documentation/arm64/cpu-feature-registers.rst.
These ID registers may imply the availability of features.
HWCAP_ASIMDRDM
Functionality implied by ID_AA64ISAR0_EL1.RDM == 0b0001.
HWCAP_JSCVT
Functionality implied by ID_AA64ISAR1_EL1.JSCVT == 0b0001.
HWCAP_FCMA
Functionality implied by ID_AA64ISAR1_EL1.FCMA == 0b0001.
HWCAP_LRCPC
Functionality implied by ID_AA64ISAR1_EL1.LRCPC == 0b0001.
HWCAP_DCPOP
Functionality implied by ID_AA64ISAR1_EL1.DPB == 0b0001.
HWCAP2_DCPODP
......@@ -140,27 +124,21 @@ HWCAP2_DCPODP
Functionality implied by ID_AA64ISAR1_EL1.DPB == 0b0010.
HWCAP_SHA3
Functionality implied by ID_AA64ISAR0_EL1.SHA3 == 0b0001.
HWCAP_SM3
Functionality implied by ID_AA64ISAR0_EL1.SM3 == 0b0001.
HWCAP_SM4
Functionality implied by ID_AA64ISAR0_EL1.SM4 == 0b0001.
HWCAP_ASIMDDP
Functionality implied by ID_AA64ISAR0_EL1.DP == 0b0001.
HWCAP_SHA512
Functionality implied by ID_AA64ISAR0_EL1.SHA2 == 0b0010.
HWCAP_SVE
Functionality implied by ID_AA64PFR0_EL1.SVE == 0b0001.
HWCAP2_SVE2
......@@ -188,23 +166,18 @@ HWCAP2_SVESM4
Functionality implied by ID_AA64ZFR0_EL1.SM4 == 0b0001.
HWCAP_ASIMDFHM
Functionality implied by ID_AA64ISAR0_EL1.FHM == 0b0001.
HWCAP_DIT
Functionality implied by ID_AA64PFR0_EL1.DIT == 0b0001.
HWCAP_USCAT
Functionality implied by ID_AA64MMFR2_EL1.AT == 0b0001.
HWCAP_ILRCPC
Functionality implied by ID_AA64ISAR1_EL1.LRCPC == 0b0010.
HWCAP_FLAGM
Functionality implied by ID_AA64ISAR0_EL1.TS == 0b0001.
HWCAP2_FLAGM2
......@@ -212,20 +185,17 @@ HWCAP2_FLAGM2
Functionality implied by ID_AA64ISAR0_EL1.TS == 0b0010.
HWCAP_SSBS
Functionality implied by ID_AA64PFR1_EL1.SSBS == 0b0010.
HWCAP_PACA
Functionality implied by ID_AA64ISAR1_EL1.APA == 0b0001 or
ID_AA64ISAR1_EL1.API == 0b0001, as described by
Documentation/arm64/pointer-authentication.txt.
Documentation/arm64/pointer-authentication.rst.
HWCAP_PACG
Functionality implied by ID_AA64ISAR1_EL1.GPA == 0b0001 or
ID_AA64ISAR1_EL1.GPI == 0b0001, as described by
Documentation/arm64/pointer-authentication.txt.
Documentation/arm64/pointer-authentication.rst.
HWCAP2_FRINT
......
====================
HugeTLBpage on ARM64
====================
......@@ -31,8 +32,10 @@ and level of the page table.
The following hugepage sizes are supported -
CONT PTE PMD CONT PMD PUD
-------- --- -------- ---
====== ======== ==== ======== ===
- CONT PTE PMD CONT PMD PUD
====== ======== ==== ======== ===
4K: 64K 2M 32M 1G
16K: 2M 32M 1G
64K: 2M 512M 16G
====== ======== ==== ======== ===
:orphan:
==================
ARM64 Architecture
==================
.. toctree::
:maxdepth: 1
acpi_object_usage
arm-acpi
booting
cpu-feature-registers
elf_hwcaps
hugetlbpage
legacy_instructions
memory
pointer-authentication
silicon-errata
sve
tagged-pointers
.. only:: subproject and html
Indices
=======
* :ref:`genindex`
===================
Legacy instructions
===================
The arm64 port of the Linux kernel provides infrastructure to support
emulation of instructions which have been deprecated, or obsoleted in
the architecture. The infrastructure code uses undefined instruction
......@@ -9,19 +13,22 @@ The emulation mode can be controlled by writing to sysctl nodes
behaviours and the corresponding values of the sysctl nodes -
* Undef
Value: 0
Value: 0
Generates undefined instruction abort. Default for instructions that
have been obsoleted in the architecture, e.g., SWP
* Emulate
Value: 1
Value: 1
Uses software emulation. To aid migration of software, in this mode
usage of emulated instruction is traced as well as rate limited
warnings are issued. This is the default for deprecated
instructions, .e.g., CP15 barriers
* Hardware Execution
Value: 2
Value: 2
Although marked as deprecated, some implementations may support the
enabling/disabling of hardware support for the execution of these
instructions. Using hardware execution generally provides better
......@@ -38,20 +45,24 @@ individual instruction notes for further information.
Supported legacy instructions
-----------------------------
* SWP{B}
Node: /proc/sys/abi/swp
Status: Obsolete
Default: Undef (0)
:Node: /proc/sys/abi/swp
:Status: Obsolete
:Default: Undef (0)
* CP15 Barriers
Node: /proc/sys/abi/cp15_barrier
Status: Deprecated
Default: Emulate (1)
:Node: /proc/sys/abi/cp15_barrier
:Status: Deprecated
:Default: Emulate (1)
* SETEND
Node: /proc/sys/abi/setend
Status: Deprecated
Default: Emulate (1)*
Note: All the cpus on the system must have mixed endian support at EL0
for this feature to be enabled. If a new CPU - which doesn't support mixed
endian - is hotplugged in after this feature has been enabled, there could
be unexpected results in the application.
:Node: /proc/sys/abi/setend
:Status: Deprecated
:Default: Emulate (1)*
Note: All the cpus on the system must have mixed endian support at EL0
for this feature to be enabled. If a new CPU - which doesn't support mixed
endian - is hotplugged in after this feature has been enabled, there could
be unexpected results in the application.
Memory Layout on AArch64 Linux
==============================
==============================
Memory Layout on AArch64 Linux
==============================
Author: Catalin Marinas <catalin.marinas@arm.com>
......@@ -21,69 +22,69 @@ The swapper_pg_dir address is written to TTBR1 and never written to
TTBR0.
AArch64 Linux memory layout with 4KB pages + 3 levels:
AArch64 Linux memory layout with 4KB pages + 3 levels::
Start End Size Use
-----------------------------------------------------------------------
0000000000000000 0000007fffffffff 512GB user
ffffff8000000000 ffffffffffffffff 512GB kernel
Start End Size Use
-----------------------------------------------------------------------
0000000000000000 0000007fffffffff 512GB user
ffffff8000000000 ffffffffffffffff 512GB kernel
AArch64 Linux memory layout with 4KB pages + 4 levels:
AArch64 Linux memory layout with 4KB pages + 4 levels::
Start End Size Use
-----------------------------------------------------------------------
0000000000000000 0000ffffffffffff 256TB user
ffff000000000000 ffffffffffffffff 256TB kernel
Start End Size Use
-----------------------------------------------------------------------
0000000000000000 0000ffffffffffff 256TB user
ffff000000000000 ffffffffffffffff 256TB kernel
AArch64 Linux memory layout with 64KB pages + 2 levels:
AArch64 Linux memory layout with 64KB pages + 2 levels::
Start End Size Use
-----------------------------------------------------------------------
0000000000000000 000003ffffffffff 4TB user
fffffc0000000000 ffffffffffffffff 4TB kernel
Start End Size Use
-----------------------------------------------------------------------
0000000000000000 000003ffffffffff 4TB user
fffffc0000000000 ffffffffffffffff 4TB kernel
AArch64 Linux memory layout with 64KB pages + 3 levels:
AArch64 Linux memory layout with 64KB pages + 3 levels::
Start End Size Use
-----------------------------------------------------------------------
0000000000000000 0000ffffffffffff 256TB user
ffff000000000000 ffffffffffffffff 256TB kernel
Start End Size Use
-----------------------------------------------------------------------
0000000000000000 0000ffffffffffff 256TB user
ffff000000000000 ffffffffffffffff 256TB kernel
For details of the virtual kernel memory layout please see the kernel
booting log.
Translation table lookup with 4KB pages:
+--------+--------+--------+--------+--------+--------+--------+--------+
|63 56|55 48|47 40|39 32|31 24|23 16|15 8|7 0|
+--------+--------+--------+--------+--------+--------+--------+--------+
| | | | | |
| | | | | v
| | | | | [11:0] in-page offset
| | | | +-> [20:12] L3 index
| | | +-----------> [29:21] L2 index
| | +---------------------> [38:30] L1 index
| +-------------------------------> [47:39] L0 index
+-------------------------------------------------> [63] TTBR0/1
Translation table lookup with 64KB pages:
+--------+--------+--------+--------+--------+--------+--------+--------+
|63 56|55 48|47 40|39 32|31 24|23 16|15 8|7 0|
+--------+--------+--------+--------+--------+--------+--------+--------+
| | | | |
| | | | v
| | | | [15:0] in-page offset
| | | +----------> [28:16] L3 index
| | +--------------------------> [41:29] L2 index
| +-------------------------------> [47:42] L1 index
+-------------------------------------------------> [63] TTBR0/1
Translation table lookup with 4KB pages::
+--------+--------+--------+--------+--------+--------+--------+--------+
|63 56|55 48|47 40|39 32|31 24|23 16|15 8|7 0|
+--------+--------+--------+--------+--------+--------+--------+--------+
| | | | | |
| | | | | v
| | | | | [11:0] in-page offset
| | | | +-> [20:12] L3 index
| | | +-----------> [29:21] L2 index
| | +---------------------> [38:30] L1 index
| +-------------------------------> [47:39] L0 index
+-------------------------------------------------> [63] TTBR0/1
Translation table lookup with 64KB pages::
+--------+--------+--------+--------+--------+--------+--------+--------+
|63 56|55 48|47 40|39 32|31 24|23 16|15 8|7 0|
+--------+--------+--------+--------+--------+--------+--------+--------+
| | | | |
| | | | v
| | | | [15:0] in-page offset
| | | +----------> [28:16] L3 index
| | +--------------------------> [41:29] L2 index
| +-------------------------------> [47:42] L1 index
+-------------------------------------------------> [63] TTBR0/1
When using KVM without the Virtualization Host Extensions, the
......
=======================================
Pointer authentication in AArch64 Linux
=======================================
Author: Mark Rutland <mark.rutland@arm.com>
Date: 2017-07-19
This document briefly describes the provision of pointer authentication
......
Silicon Errata and Software Workarounds
=======================================
=======================================
Silicon Errata and Software Workarounds
=======================================
Author: Will Deacon <will.deacon@arm.com>
Date : 27 November 2015
It is an unfortunate fact of life that hardware is often produced with
......@@ -9,11 +11,13 @@ so-called "errata", which can cause it to deviate from the architecture
under specific circumstances. For hardware produced by ARM, these
errata are broadly classified into the following categories:
Category A: A critical error without a viable workaround.
Category B: A significant or critical error with an acceptable
========== ========================================================
Category A A critical error without a viable workaround.
Category B A significant or critical error with an acceptable
workaround.
Category C: A minor error that is not expected to occur under normal
Category C A minor error that is not expected to occur under normal
operation.
========== ========================================================
For more information, consult one of the "Software Developers Errata
Notice" documents available on infocenter.arm.com (registration
......@@ -42,47 +46,86 @@ file acts as a registry of software workarounds in the Linux Kernel and
will be updated when new workarounds are committed and backported to
stable kernels.
| Implementor | Component | Erratum ID | Kconfig |
+----------------+-----------------+-----------------+-----------------------------+
| Implementor | Component | Erratum ID | Kconfig |
+================+=================+=================+=============================+
| Allwinner | A64/R18 | UNKNOWN1 | SUN50I_ERRATUM_UNKNOWN1 |
| | | | |
+----------------+-----------------+-----------------+-----------------------------+
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A53 | #826319 | ARM64_ERRATUM_826319 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A53 | #827319 | ARM64_ERRATUM_827319 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A53 | #824069 | ARM64_ERRATUM_824069 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A53 | #819472 | ARM64_ERRATUM_819472 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A53 | #845719 | ARM64_ERRATUM_845719 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A53 | #843419 | ARM64_ERRATUM_843419 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A57 | #832075 | ARM64_ERRATUM_832075 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A57 | #852523 | N/A |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A57 | #834220 | ARM64_ERRATUM_834220 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A72 | #853709 | N/A |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A73 | #858921 | ARM64_ERRATUM_858921 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A55 | #1024718 | ARM64_ERRATUM_1024718 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A76 | #1188873,1418040| ARM64_ERRATUM_1418040 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A76 | #1165522 | ARM64_ERRATUM_1165522 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A76 | #1286807 | ARM64_ERRATUM_1286807 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A76 | #1463225 | ARM64_ERRATUM_1463225 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Neoverse-N1 | #1188873,1418040| ARM64_ERRATUM_1418040 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | MMU-500 | #841119,826419 | N/A |
| | | | |
+----------------+-----------------+-----------------+-----------------------------+
+----------------+-----------------+-----------------+-----------------------------+
| Cavium | ThunderX ITS | #22375,24313 | CAVIUM_ERRATUM_22375 |
+----------------+-----------------+-----------------+-----------------------------+
| Cavium | ThunderX ITS | #23144 | CAVIUM_ERRATUM_23144 |
+----------------+-----------------+-----------------+-----------------------------+
| Cavium | ThunderX GICv3 | #23154 | CAVIUM_ERRATUM_23154 |
+----------------+-----------------+-----------------+-----------------------------+
| Cavium | ThunderX Core | #27456 | CAVIUM_ERRATUM_27456 |
+----------------+-----------------+-----------------+-----------------------------+
| Cavium | ThunderX Core | #30115 | CAVIUM_ERRATUM_30115 |
+----------------+-----------------+-----------------+-----------------------------+
| Cavium | ThunderX SMMUv2 | #27704 | N/A |
+----------------+-----------------+-----------------+-----------------------------+
| Cavium | ThunderX2 SMMUv3| #74 | N/A |
+----------------+-----------------+-----------------+-----------------------------+
| Cavium | ThunderX2 SMMUv3| #126 | N/A |
| | | | |
+----------------+-----------------+-----------------+-----------------------------+
+----------------+-----------------+-----------------+-----------------------------+
| Freescale/NXP | LS2080A/LS1043A | A-008585 | FSL_ERRATUM_A008585 |
| | | | |
+----------------+-----------------+-----------------+-----------------------------+
+----------------+-----------------+-----------------+-----------------------------+
| Hisilicon | Hip0{5,6,7} | #161010101 | HISILICON_ERRATUM_161010101 |
+----------------+-----------------+-----------------+-----------------------------+
| Hisilicon | Hip0{6,7} | #161010701 | N/A |
+----------------+-----------------+-----------------+-----------------------------+
| Hisilicon | Hip07 | #161600802 | HISILICON_ERRATUM_161600802 |
+----------------+-----------------+-----------------+-----------------------------+
| Hisilicon | Hip08 SMMU PMCG | #162001800 | N/A |
| | | | |
+----------------+-----------------+-----------------+-----------------------------+
+----------------+-----------------+-----------------+-----------------------------+
| Qualcomm Tech. | Kryo/Falkor v1 | E1003 | QCOM_FALKOR_ERRATUM_1003 |
+----------------+-----------------+-----------------+-----------------------------+
| Qualcomm Tech. | Falkor v1 | E1009 | QCOM_FALKOR_ERRATUM_1009 |
+----------------+-----------------+-----------------+-----------------------------+
| Qualcomm Tech. | QDF2400 ITS | E0065 | QCOM_QDF2400_ERRATUM_0065 |
+----------------+-----------------+-----------------+-----------------------------+
| Qualcomm Tech. | Falkor v{1,2} | E1041 | QCOM_FALKOR_ERRATUM_1041 |
+----------------+-----------------+-----------------+-----------------------------+
+----------------+-----------------+-----------------+-----------------------------+
| Fujitsu | A64FX | E#010001 | FUJITSU_ERRATUM_010001 |
+----------------+-----------------+-----------------+-----------------------------+
Scalable Vector Extension support for AArch64 Linux
===================================================
===================================================
Scalable Vector Extension support for AArch64 Linux
===================================================
Author: Dave Martin <Dave.Martin@arm.com>
Date: 4 August 2017
This document outlines briefly the interface provided to userspace by Linux in
......@@ -442,7 +444,7 @@ In A64 state, SVE adds the following:
* FPSR and FPCR are retained from ARMv8-A, and interact with SVE floating-point
operations in a similar way to the way in which they interact with ARMv8
floating-point operations.
floating-point operations::
8VL-1 128 0 bit index
+---- //// -----------------+
......@@ -499,6 +501,8 @@ ARMv8-A defines the following floating-point / SIMD register state:
* 32 128-bit vector registers V0..V31
* 2 32-bit status/control registers FPSR, FPCR
::
127 0 bit index
+---------------+
V0 | |
......@@ -533,7 +537,7 @@ References
[2] arch/arm64/include/uapi/asm/ptrace.h
AArch64 Linux ptrace ABI definitions
[3] Documentation/arm64/cpu-feature-registers.txt
[3] Documentation/arm64/cpu-feature-registers.rst
[4] ARM IHI0055C
http://infocenter.arm.com/help/topic/com.arm.doc.ihi0055c/IHI0055C_beta_aapcs64.pdf
......
Tagged virtual addresses in AArch64 Linux
=========================================
=========================================
Tagged virtual addresses in AArch64 Linux
=========================================
Author: Will Deacon <will.deacon@arm.com>
Date : 12 June 2013
This document briefly describes the provision of tagged virtual
......
......@@ -151,6 +151,7 @@ for the type. The maximum value of ``BTF_INT_BITS()`` is 128.
The ``BTF_INT_OFFSET()`` specifies the starting bit offset to calculate values
for this int. For example, a bitfield struct member has:
* btf member bit offset 100 from the start of the structure,
* btf member pointing to an int type,
* the int type has ``BTF_INT_OFFSET() = 2`` and ``BTF_INT_BITS() = 4``
......@@ -160,6 +161,7 @@ from bits ``100 + 2 = 102``.
Alternatively, the bitfield struct member can be the following to access the
same bits as the above:
* btf member bit offset 102,
* btf member pointing to an int type,
* the int type has ``BTF_INT_OFFSET() = 0`` and ``BTF_INT_BITS() = 4``
......
LATEXFILE = cdrom-standard
all:
make clean
latex $(LATEXFILE)
latex $(LATEXFILE)
@if [ -x `which gv` ]; then \
`dvips -q -t letter -o $(LATEXFILE).ps $(LATEXFILE).dvi` ;\
`gv -antialias -media letter -nocenter $(LATEXFILE).ps` ;\
else \
`xdvi $(LATEXFILE).dvi &` ;\
fi
make sortofclean
clean:
rm -f $(LATEXFILE).ps $(LATEXFILE).dvi $(LATEXFILE).aux $(LATEXFILE).log
sortofclean:
rm -f $(LATEXFILE).aux $(LATEXFILE).log
This diff is collapsed.
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:orphan:
=====
cdrom
=====
.. toctree::
:maxdepth: 1
cdrom-standard
ide-cd
packet-writing
.. only:: subproject and html
Indices
=======
* :ref:`genindex`
==============
Packet writing
==============
Getting started quick
---------------------
......@@ -10,13 +14,16 @@ Getting started quick
Download from http://sourceforge.net/projects/linux-udf/
- Grab a new CD-RW disc and format it (assuming CD-RW is hdc, substitute
as appropriate):
as appropriate)::
# cdrwtool -d /dev/hdc -q
- Setup your writer
- Setup your writer::
# pktsetup dev_name /dev/hdc
- Now you can mount /dev/pktcdvd/dev_name and copy files to it. Enjoy!
- Now you can mount /dev/pktcdvd/dev_name and copy files to it. Enjoy::
# mount /dev/pktcdvd/dev_name /cdrom -t udf -o rw,noatime
......@@ -25,11 +32,11 @@ Packet writing for DVD-RW media
DVD-RW discs can be written to much like CD-RW discs if they are in
the so called "restricted overwrite" mode. To put a disc in restricted
overwrite mode, run:
overwrite mode, run::
# dvd+rw-format /dev/hdc
You can then use the disc the same way you would use a CD-RW disc:
You can then use the disc the same way you would use a CD-RW disc::
# pktsetup dev_name /dev/hdc
# mount /dev/pktcdvd/dev_name /cdrom -t udf -o rw,noatime
......@@ -41,7 +48,7 @@ Packet writing for DVD+RW media
According to the DVD+RW specification, a drive supporting DVD+RW discs
shall implement "true random writes with 2KB granularity", which means
that it should be possible to put any filesystem with a block size >=
2KB on such a disc. For example, it should be possible to do:
2KB on such a disc. For example, it should be possible to do::
# dvd+rw-format /dev/hdc (only needed if the disc has never
been formatted)
......@@ -54,7 +61,7 @@ follow the specification, but suffer bad performance problems if the
writes are not 32KB aligned.
Both problems can be solved by using the pktcdvd driver, which always
generates aligned writes.
generates aligned writes::
# dvd+rw-format /dev/hdc
# pktsetup dev_name /dev/hdc
......@@ -83,7 +90,7 @@ Notes
- Since the pktcdvd driver makes the disc appear as a regular block
device with a 2KB block size, you can put any filesystem you like on
the disc. For example, run:
the disc. For example, run::
# /sbin/mke2fs /dev/pktcdvd/dev_name
......@@ -97,7 +104,7 @@ Since Linux 2.6.20, the pktcdvd module has a sysfs interface
and can be controlled by it. For example the "pktcdvd" tool uses
this interface. (see http://tom.ist-im-web.de/download/pktcdvd )
"pktcdvd" works similar to "pktsetup", e.g.:
"pktcdvd" works similar to "pktsetup", e.g.::
# pktcdvd -a dev_name /dev/hdc
# mkudffs /dev/pktcdvd/dev_name
......@@ -115,7 +122,7 @@ For a description of the sysfs interface look into the file:
Using the pktcdvd debugfs interface
-----------------------------------
To read pktcdvd device infos in human readable form, do:
To read pktcdvd device infos in human readable form, do::
# cat /sys/kernel/debug/pktcdvd/pktcdvd[0-7]/info
......
......@@ -34,7 +34,8 @@ needs_sphinx = '1.3'
# Add any Sphinx extension module names here, as strings. They can be
# extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
# ones.
extensions = ['kerneldoc', 'rstFlatTable', 'kernel_include', 'cdomain', 'kfigure', 'sphinx.ext.ifconfig']
extensions = ['kerneldoc', 'rstFlatTable', 'kernel_include', 'cdomain',
'kfigure', 'sphinx.ext.ifconfig', 'automarkup']
# The name of the math extension changed on Sphinx 1.4
if (major == 1 and minor > 3) or (major > 1):
......@@ -200,7 +201,7 @@ html_context = {
# If true, SmartyPants will be used to convert quotes and dashes to
# typographically correct entities.
#html_use_smartypants = True
html_use_smartypants = False
# Custom sidebar templates, maps document names to template names.
#html_sidebars = {}
......
......@@ -34,6 +34,8 @@ Core utilities
timekeeping
boot-time-mm
memory-hotplug
protection-keys
../RCU/index
Interfaces for kernel debugging
......
......@@ -33,6 +33,9 @@ String Conversions
.. kernel-doc:: lib/kstrtox.c
:export:
.. kernel-doc:: lib/string_helpers.c
:export:
String Manipulation
-------------------
......@@ -138,6 +141,15 @@ Base 2 log and power Functions
.. kernel-doc:: include/linux/log2.h
:internal:
Integer power Functions
-----------------------
.. kernel-doc:: lib/math/int_pow.c
:export:
.. kernel-doc:: lib/math/int_sqrt.c
:export:
Division Functions
------------------
......@@ -358,8 +370,6 @@ Read-Copy Update (RCU)
.. kernel-doc:: kernel/rcu/tree.c
.. kernel-doc:: kernel/rcu/tree_plugin.h
.. kernel-doc:: kernel/rcu/tree_exp.h
.. kernel-doc:: kernel/rcu/update.c
......
......@@ -115,7 +115,7 @@ Some additional variants exist for more specialized cases:
void ktime_get_coarse_clocktai_ts64( struct timespec64 * )
These are quicker than the non-coarse versions, but less accurate,
corresponding to CLOCK_MONONOTNIC_COARSE and CLOCK_REALTIME_COARSE
corresponding to CLOCK_MONOTONIC_COARSE and CLOCK_REALTIME_COARSE
in user space, along with the equivalent boottime/tai/raw
timebase not available in user space.
......
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=============================
Guidance for writing policies
=============================
......@@ -30,7 +31,7 @@ multiqueue (mq)
This policy is now an alias for smq (see below).
The following tunables are accepted, but have no effect:
The following tunables are accepted, but have no effect::
'sequential_threshold <#nr_sequential_ios>'
'random_threshold <#nr_random_ios>'
......@@ -56,7 +57,9 @@ mq policy's hints to be dropped. Also, performance of the cache may
degrade slightly until smq recalculates the origin device's hotspots
that should be cached.
Memory usage:
Memory usage
^^^^^^^^^^^^
The mq policy used a lot of memory; 88 bytes per cache block on a 64
bit machine.
......@@ -69,7 +72,9 @@ cache block).
All this means smq uses ~25bytes per cache block. Still a lot of
memory, but a substantial improvement nontheless.
Level balancing:
Level balancing
^^^^^^^^^^^^^^^
mq placed entries in different levels of the multiqueue structures
based on their hit count (~ln(hit count)). This meant the bottom
levels generally had the most entries, and the top ones had very
......@@ -94,7 +99,9 @@ is used to decide which blocks to promote. If the hotspot queue is
performing badly then it starts moving entries more quickly between
levels. This lets it adapt to new IO patterns very quickly.
Performance:
Performance
^^^^^^^^^^^
Testing smq shows substantially better performance than mq.
cleaner
......@@ -105,16 +112,19 @@ The cleaner writes back all dirty blocks in a cache to decommission it.
Examples
========
The syntax for a table is:
The syntax for a table is::
cache <metadata dev> <cache dev> <origin dev> <block size>
<#feature_args> [<feature arg>]*
<policy> <#policy_args> [<policy arg>]*
The syntax to send a message using the dmsetup command is:
The syntax to send a message using the dmsetup command is::
dmsetup message <mapped device> 0 sequential_threshold 1024
dmsetup message <mapped device> 0 random_threshold 8
Using dmsetup:
Using dmsetup::
dmsetup create blah --table "0 268435456 cache /dev/sdb /dev/sdc \
/dev/sdd 512 0 mq 4 sequential_threshold 1024 random_threshold 8"
creates a 128GB large mapped device named 'blah' with the
......
=====================
Device-Mapper Logging
=====================
The device-mapper logging code is used by some of the device-mapper
......@@ -16,11 +17,13 @@ dm_dirty_log_type in include/linux/dm-dirty-log.h). Various different
logging implementations are available and provide different
capabilities. The list includes:
============== ==============================================================
Type Files
==== =====
============== ==============================================================
disk drivers/md/dm-log.c
core drivers/md/dm-log.c
userspace drivers/md/dm-log-userspace* include/linux/dm-log-userspace.h
============== ==============================================================
The "disk" log type
-------------------
......
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