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Commit 263a19ff authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab Committed by Paolo Bonzini
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docs: virt: Convert msr.txt to ReST format 

- Use document title markup;
- Convert tables;
- Add blank lines and adjust indentation.
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 2756df60
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Documentation/virt/kvm/index.rst
View file @ 263a19ff
......@@ -10,6 +10,7 @@ KVM
amd-memory-encryption
cpuid
halt-polling
msr
vcpu-requests
arm/index
Documentation/virt/kvm/msr.txt → Documentation/virt/kvm/msr.rst
View file @ 263a19ff
KVM-specific MSRs.
Glauber Costa <glommer@redhat.com>, Red Hat Inc, 2010
=====================================================
.. SPDX-License-Identifier: GPL-2.0
=================
KVM-specific MSRs
=================
:Author: Glauber Costa <glommer@redhat.com>, Red Hat Inc, 2010
KVM makes use of some custom MSRs to service some requests.
......@@ -9,15 +13,17 @@ Custom MSRs have a range reserved for them, that goes from
but they are deprecated and their use is discouraged.
Custom MSR list
--------
---------------
The current supported Custom MSR list is:
MSR_KVM_WALL_CLOCK_NEW: 0x4b564d00
MSR_KVM_WALL_CLOCK_NEW:
0x4b564d00
data: 4-byte alignment physical address of a memory area which must be
data:
4-byte alignment physical address of a memory area which must be
in guest RAM. This memory is expected to hold a copy of the following
structure:
structure::
struct pvclock_wall_clock {
u32 version;
......@@ -30,13 +36,16 @@ MSR_KVM_WALL_CLOCK_NEW: 0x4b564d00
Users that want to reliably query this information more than once have
to write more than once to this MSR. Fields have the following meanings:
version: guest has to check version before and after grabbing
version:
guest has to check version before and after grabbing
time information and check that they are both equal and even.
An odd version indicates an in-progress update.
sec: number of seconds for wallclock at time of boot.
sec:
number of seconds for wallclock at time of boot.
nsec: number of nanoseconds for wallclock at time of boot.
nsec:
number of nanoseconds for wallclock at time of boot.
In order to get the current wallclock time, the system_time from
MSR_KVM_SYSTEM_TIME_NEW needs to be added.
......@@ -47,11 +56,13 @@ MSR_KVM_WALL_CLOCK_NEW: 0x4b564d00
Availability of this MSR must be checked via bit 3 in 0x4000001 cpuid
leaf prior to usage.
MSR_KVM_SYSTEM_TIME_NEW: 0x4b564d01
MSR_KVM_SYSTEM_TIME_NEW:
0x4b564d01
data: 4-byte aligned physical address of a memory area which must be in
data:
4-byte aligned physical address of a memory area which must be in
guest RAM, plus an enable bit in bit 0. This memory is expected to hold
a copy of the following structure:
a copy of the following structure::
struct pvclock_vcpu_time_info {
u32 version;
......@@ -72,23 +83,28 @@ MSR_KVM_SYSTEM_TIME_NEW: 0x4b564d01
Fields have the following meanings:
version: guest has to check version before and after grabbing
version:
guest has to check version before and after grabbing
time information and check that they are both equal and even.
An odd version indicates an in-progress update.
tsc_timestamp: the tsc value at the current VCPU at the time
tsc_timestamp:
the tsc value at the current VCPU at the time
of the update of this structure. Guests can subtract this value
from current tsc to derive a notion of elapsed time since the
structure update.
system_time: a host notion of monotonic time, including sleep
system_time:
a host notion of monotonic time, including sleep
time at the time this structure was last updated. Unit is
nanoseconds.
tsc_to_system_mul: multiplier to be used when converting
tsc_to_system_mul:
multiplier to be used when converting
tsc-related quantity to nanoseconds
tsc_shift: shift to be used when converting tsc-related
tsc_shift:
shift to be used when converting tsc-related
quantity to nanoseconds. This shift will ensure that
multiplication with tsc_to_system_mul does not overflow.
A positive value denotes a left shift, a negative value
......@@ -96,7 +112,7 @@ MSR_KVM_SYSTEM_TIME_NEW: 0x4b564d01
The conversion from tsc to nanoseconds involves an additional
right shift by 32 bits. With this information, guests can
derive per-CPU time by doing:
derive per-CPU time by doing::
time = (current_tsc - tsc_timestamp)
if (tsc_shift >= 0)
......@@ -106,29 +122,34 @@ MSR_KVM_SYSTEM_TIME_NEW: 0x4b564d01
time = (time * tsc_to_system_mul) >> 32
time = time + system_time
flags: bits in this field indicate extended capabilities
flags:
bits in this field indicate extended capabilities
coordinated between the guest and the hypervisor. Availability
of specific flags has to be checked in 0x40000001 cpuid leaf.
Current flags are:
flag bit | cpuid bit | meaning
-------------------------------------------------------------
| | time measures taken across
0 | 24 | multiple cpus are guaranteed to
| | be monotonic
-------------------------------------------------------------
| | guest vcpu has been paused by
1 | N/A | the host
| | See 4.70 in api.txt
-------------------------------------------------------------
+-----------+--------------+----------------------------------+
| flag bit | cpuid bit | meaning |
+-----------+--------------+----------------------------------+
| | | time measures taken across |
| 0 | 24 | multiple cpus are guaranteed to |
| | | be monotonic |
+-----------+--------------+----------------------------------+
| | | guest vcpu has been paused by |
| 1 | N/A | the host |
| | | See 4.70 in api.txt |
+-----------+--------------+----------------------------------+
Availability of this MSR must be checked via bit 3 in 0x4000001 cpuid
leaf prior to usage.
MSR_KVM_WALL_CLOCK: 0x11
MSR_KVM_WALL_CLOCK:
0x11
data and functioning: same as MSR_KVM_WALL_CLOCK_NEW. Use that instead.
data and functioning:
same as MSR_KVM_WALL_CLOCK_NEW. Use that instead.
This MSR falls outside the reserved KVM range and may be removed in the
future. Its usage is deprecated.
......@@ -136,9 +157,11 @@ MSR_KVM_WALL_CLOCK: 0x11
Availability of this MSR must be checked via bit 0 in 0x4000001 cpuid
leaf prior to usage.
MSR_KVM_SYSTEM_TIME: 0x12
MSR_KVM_SYSTEM_TIME:
0x12
data and functioning: same as MSR_KVM_SYSTEM_TIME_NEW. Use that instead.
data and functioning:
same as MSR_KVM_SYSTEM_TIME_NEW. Use that instead.
This MSR falls outside the reserved KVM range and may be removed in the
future. Its usage is deprecated.
......@@ -146,7 +169,7 @@ MSR_KVM_SYSTEM_TIME: 0x12
Availability of this MSR must be checked via bit 0 in 0x4000001 cpuid
leaf prior to usage.
The suggested algorithm for detecting kvmclock presence is then:
The suggested algorithm for detecting kvmclock presence is then::
if (!kvm_para_available()) /* refer to cpuid.txt */
return NON_PRESENT;
......@@ -163,8 +186,11 @@ MSR_KVM_SYSTEM_TIME: 0x12
} else
return NON_PRESENT;
MSR_KVM_ASYNC_PF_EN: 0x4b564d02
data: Bits 63-6 hold 64-byte aligned physical address of a
MSR_KVM_ASYNC_PF_EN:
0x4b564d02
data:
Bits 63-6 hold 64-byte aligned physical address of a
64 byte memory area which must be in guest RAM and must be
zeroed. Bits 5-3 are reserved and should be zero. Bit 0 is 1
when asynchronous page faults are enabled on the vcpu 0 when
......@@ -200,11 +226,13 @@ MSR_KVM_ASYNC_PF_EN: 0x4b564d02
Currently type 2 APF will be always delivered on the same vcpu as
type 1 was, but guest should not rely on that.
MSR_KVM_STEAL_TIME: 0x4b564d03
MSR_KVM_STEAL_TIME:
0x4b564d03
data: 64-byte alignment physical address of a memory area which must be
data:
64-byte alignment physical address of a memory area which must be
in guest RAM, plus an enable bit in bit 0. This memory is expected to
hold a copy of the following structure:
hold a copy of the following structure::
struct kvm_steal_time {
__u64 steal;
......@@ -224,25 +252,32 @@ MSR_KVM_STEAL_TIME: 0x4b564d03
Fields have the following meanings:
version: a sequence counter. In other words, guest has to check
version:
a sequence counter. In other words, guest has to check
this field before and after grabbing time information and make
sure they are both equal and even. An odd version indicates an
in-progress update.
flags: At this point, always zero. May be used to indicate
flags:
At this point, always zero. May be used to indicate
changes in this structure in the future.
steal: the amount of time in which this vCPU did not run, in
steal:
the amount of time in which this vCPU did not run, in
nanoseconds. Time during which the vcpu is idle, will not be
reported as steal time.
preempted: indicate the vCPU who owns this struct is running or
preempted:
indicate the vCPU who owns this struct is running or
not. Non-zero values mean the vCPU has been preempted. Zero
means the vCPU is not preempted. NOTE, it is always zero if the
the hypervisor doesn't support this field.
MSR_KVM_EOI_EN: 0x4b564d04
data: Bit 0 is 1 when PV end of interrupt is enabled on the vcpu; 0
MSR_KVM_EOI_EN:
0x4b564d04
data:
Bit 0 is 1 when PV end of interrupt is enabled on the vcpu; 0
when disabled. Bit 1 is reserved and must be zero. When PV end of
interrupt is enabled (bit 0 set), bits 63-2 hold a 4-byte aligned
physical address of a 4 byte memory area which must be in guest RAM and
......@@ -274,11 +309,13 @@ MSR_KVM_EOI_EN: 0x4b564d04
clear it using a single CPU instruction, such as test and clear, or
compare and exchange.
MSR_KVM_POLL_CONTROL: 0x4b564d05
MSR_KVM_POLL_CONTROL:
0x4b564d05
Control host-side polling.
data: Bit 0 enables (1) or disables (0) host-side HLT polling logic.
data:
Bit 0 enables (1) or disables (0) host-side HLT polling logic.
KVM guests can request the host not to poll on HLT, for example if
they are performing polling themselves.
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