The powerpc mobility code may receive RTAS requests to perform PRRN
(Platform Resource Reassignment Notification) topology changes at any
time, including during LPAR migration operations.

In some configurations where the affinity of CPUs or memory is being
changed on that platform, the PRRN requests may apply or refer to
outdated information prior to the complete update of the device-tree.

This patch changes the duration for which topology updates are
suppressed during LPAR migrations from just the rtas_ibm_suspend_me()
/ 'ibm,suspend-me' call(s) to cover the entire migration_store()
operation to allow all changes to the device-tree to be applied prior
to accepting and applying any PRRN requests.

For tracking purposes, pr_info notices are added to the functions
start_topology_update() and stop_topology_update() of 'numa.c'.
Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com>
Reviewed-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Ever since commit 15a3204d ("powerpc/64s: Set assembler machine type
to POWER4") we force -mpower4 to be passed to the assembler
irrespective of the CFLAGS used (for Book3s 64).

When building a powerpc64 kernel with clang, clang will not add -many
to the assembler flags, so any instructions that the compiler has
generated that are not available on power4 will cause an error:

  /usr/bin/as -a64 -mppc64 -mlittle-endian -mpower8 \
   -I ./arch/powerpc/include -I ./arch/powerpc/include/generated \
   -I ./include -I ./arch/powerpc/include/uapi \
   -I ./arch/powerpc/include/generated/uapi -I ./include/uapi \
   -I ./include/generated/uapi -I arch/powerpc -I arch/powerpc \
   -maltivec -mpower4 -o init/do_mounts.o /tmp/do_mounts-3b0a3d.s
  /tmp/do_mounts-51ce54.s:748: Error: unrecognized opcode: `isel'

GCC does include -many, so the GCC driven gas call will succeed:

  as -v -I ./arch/powerpc/include -I ./arch/powerpc/include/generated -I
  ./include -I ./arch/powerpc/include/uapi
  -I ./arch/powerpc/include/generated/uapi -I ./include/uapi
  -I ./include/generated/uapi -I arch/powerpc -I arch/powerpc
   -a64 -mpower8 -many -mlittle -maltivec -mpower4 -o init/do_mounts.o

Note that isel is power7 and above for IBM CPUs. GCC only generates it
for Power9 and above, but the above test was run against the clang
generated assembly.

Peter Bergner explains:

  When using -many -mpower4, gas will first try and find a matching
  power4 mnemonic and failing that, it will then allow any valid
  mnemonic that gas knows about. GCC's use of -many predates me
  though.

  IIRC, Alan looked at trying to remove it, but I forget why he
  didn't. Could be either a gcc or gas issue at the time. I'm not sure
  whether issue still exists or not. He and I have modified how gas
  works internally a fair amount since he tried removing gcc use of
  -many.

  I will also note that when using -many, gas will choose the first
  mnemonic that matches in the mnemonic table and we have (mostly)
  sorted the table so that server mnemonics show up earlier in the
  table than other mnemonics, so they'll be seen/chosen first.

By explicitly setting -many we can build with Clang and GCC while
retaining the -mpower4 option.
Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

The variable 'aa_index' is defined as an unsigned value in
update_lmb_associativity_index(), but find_aa_index() may return -1
when dlpar_clone_property() fails. So change find_aa_index() to return
a bool, which indicates whether 'aa_index' was found or not.

Fixes: c05a5a40 ("powerpc/pseries: Dynamic add entires to associativity lookup array")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Nathan Fontenot nfont@linux.vnet.ibm.com>
[mpe: Tweak changelog, rename is_found to just found]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Rather than mixing "if (state)" blocks and gotos, convert entirely to
"if (state)" blocks to make the state machine behaviour clearer.
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

The wait_state member of eeh_ops does not need to be platform
dependent; it's just logic around eeh_ops.get_state(). Therefore,
merge the two (slightly different!) platform versions into a new
function, eeh_wait_state() and remove the eeh_ops member.

While doing this, also correct:
* The wait logic, so that it never waits longer than max_wait.
* The wait logic, so that it never waits less than
  EEH_STATE_MIN_WAIT_TIME.
* One call site where the result is treated like a bit field before
  it's checked for negative error values.
* In pseries_eeh_get_state(), rename the "state" parameter to "delay"
  because that's what it is.
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Currently, eeh_pe_state_mark() marks a PE (and it's children) with a
state and then performs additional processing if that state included
EEH_PE_ISOLATED.

The state parameter is always a constant at the call site, so
rearrange eeh_pe_state_mark() into two functions and just call the
appropriate one at each site.
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

The function eeh_pe_state_mark_with_cfg() just performs the work of
eeh_pe_state_mark() and then, conditionally, the work of
eeh_pe_state_clear(). However it is only ever called with a constant
state such that the condition is always true, so replace it by direct
calls.
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Move the call to eeh_dev_to_pe() up, so that later it's clear that
"pe" isn't NULL.
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Change the name of the fields in eeh_rmv_data to clarify their usage.

Change "edev_list" to "removed_vf_list" because it does not contain
generic edevs, but rather only edevs that contain virtual functions
(which need to be removed during recovery).

Similarly, change "removed" to "removed_dev_count" because it is a
count of any removed devices, not just those in the above list.
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Instances of struct eeh_pe are placed in a tree structure using the
fields "child_list" and "child", so place these next to each other
in the definition.

The field "child" is a list entry, so remove the unnecessary and
misleading use of the list initializer, LIST_HEAD(), on it.

The eeh_dev struct contains two list entry fields, called "list" and
"rmv_list". Rename them to "entry" and "rmv_entry" and, as above, stop
initializing them with LIST_HEAD().
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Remove the unnecessary cast through void * on the first parameter and
remove the unused second parameter (always NULL).
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

The 'bus' member of struct eeh_dev is assigned to once but never used,
so remove it.
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Currently a flag, EEH_POSTPONED_PROBE, is used to prevent an incorrect
message "EEH: No capable adapters found" from being displayed during
the boot of powernv systems.

It is necessary because, on powernv, the call to eeh_probe_devices()
made from eeh_init() is too early and EEH can't yet be enabled. A
second call is made later from eeh_pnv_post_init(), which succeeds.

(On pseries, the first call succeeds because PCI devices are set up
early enough and no second call is made.)

This can be simplified by moving the early call to eeh_probe_devices()
from eeh_init() (where it's seen by both platforms) to
pSeries_final_fixup(), so that each platform only calls
eeh_probe_devices() once, at a point where it can succeed.
This is slightly later in the boot sequence, but but still early
enough and it is now in the same place in the sequence for both
platforms (the pcibios_fixup hook).

The display of the message can be cleaned up as well, by moving it
into eeh_probe_devices().
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

eeh_add_to_parent_pe() sometimes removes the EEH_PE_KEEP flag, but it
incorrectly removes it from pe->type, instead of pe->state.

However, rather than clearing it from the correct field, remove it.
Inspection of the code shows that it can't ever have had any effect
(even if it had been cleared from the correct field), because the
field is never tested after it is cleared by the statement in
question.

The clear statement was added by commit 807a827d ("powerpc/eeh:
Keep PE during hotplug"), but it didn't explain why it was necessary.
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

If a device is removed during EEH processing (either by a driver's
handler or as part of recovery), it can lead to a null dereference
in eeh_pe_report_edev().

To handle this, skip devices that have been removed.
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

If an error occurs during an unplug operation, it's possible for
eeh_dump_dev_log() to be called when edev->pdn is null, which
currently leads to dereferencing a null pointer.

Handle this by skipping the error log for those devices.
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

The boot wrapper is currently built with -Os. By building with O2 we
can meaningfully reduce the time decompressing the kernel.

I tested by comparing 10 runs of each option in Qemu and on hardware.
The kernel is compressed with KERNEL_XZ built with GCC 8.2.0-7ubuntu1.
The values are counts of the timebase.

Qemu TCG powernv Power8:

              Os            O2            O3
 median       10221123889   6201518438    6568186825
 stddev        1361267211    429090641     657930076
 improvement                    39.33%        35.74%

Palmetto Power8:

              Os            O2            O3
 median           50279         50599          35790
 stddev       992144533     627130655      623721078
 improvement                   36.79%         37.13%

Romulus Power9:

              Os            O2            O3
 median       670312391     454733720      448881398
 stddev          157569        107276         108760
 improvement                   32.16%         33.03%

TCG was quite noisy, with every few runs producing an outlier. Even so,
O2 is faster than O3. On hardware the numbers were less noisy and O3 is
slightly faster than O2.

The wrapper size increases when moving from Os. Comparing zImage.epapr
to the existing Os build using bloat-o-meter:

  Before=43401, After=56837 (13KB), chg +30.96%
  Before=43401, After=64305 (20KB), chg +48.16%

I chose O2 for a balance between Qemu and hardware speed up.
Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

This will avoid auto-vectorisation when building with higher
optimisation levels.

We don't know if the machine can support VSX and even if it's present
it's probably not going to be enabled at this point in boot.

These flag were both added prior to GCC 4.6 which is the minimum
compiler version supported by upstream, thanks to Segher for the
details.
Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

As of commit 10c77dba ("powerpc/boot: Fix build failure in 32-bit
boot wrapper") the opal code is hidden behind CONFIG_PPC64_BOOT_WRAPPER,
but the boot wrapper avoids include/linux, so it does not get the normal
Kconfig flags.

We can drop the guard entirely as in commit f8e8e69c ("powerpc/boot:
Only build OPAL code when necessary") the makefile only includes opal.c
in the build if CONFIG_PPC64_BOOT_WRAPPER is set.

Fixes: 10c77dba ("powerpc/boot: Fix build failure in 32-bit boot wrapper")
Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Currently the wrapper is built without including anything in
$(src)/include/, which means there are no CONFIG_ symbols defined.
This means the platform specific serial drivers were never enabled.

We now copy the definitions into the boot directory, so any C file can
now include autoconf.h to depend on configuration options.

Fixes: 866bfc75 ("powerpc: conditionally compile platform-specific serial drivers")
Signed-off-by: Joel Stanley <joel@jms.id.au>
[mpe: Fix to use $(objtree) to find autoconf.h]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

'default n' is the default value for any bool or tristate Kconfig
setting so there is no need to write it explicitly.

Also since commit f467c564 ("kconfig: only write '# CONFIG_FOO
is not set' for visible symbols") the Kconfig behavior is the same
regardless of 'default n' being present or not:

    ...
    One side effect of (and the main motivation for) this change is making
    the following two definitions behave exactly the same:

        config FOO
                bool

        config FOO
                bool
                default n

    With this change, neither of these will generate a
    '# CONFIG_FOO is not set' line (assuming FOO isn't selected/implied).
    That might make it clearer to people that a bare 'default n' is
    redundant.
    ...
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Currently when we get an unknown RTAS event it prints the type as
"Unknown" and no other useful information. Add the raw type code to the
log message so that we have something to work off.
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Reviewed-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

The powerpc kernel uses setjmp which causes a warning when building
with clang:

  In file included from arch/powerpc/xmon/xmon.c:51:
  ./arch/powerpc/include/asm/setjmp.h:15:13: error: declaration of
  built-in function 'setjmp' requires inclusion of the header <setjmp.h>
        [-Werror,-Wbuiltin-requires-header]
  extern long setjmp(long *);
              ^
  ./arch/powerpc/include/asm/setjmp.h:16:13: error: declaration of
  built-in function 'longjmp' requires inclusion of the header <setjmp.h>
        [-Werror,-Wbuiltin-requires-header]
  extern void longjmp(long *, long);
              ^

This *is* the header and we're not using the built-in setjump but
rather the one in arch/powerpc/kernel/misc.S. As the compiler warning
does not make sense, it for the files where setjmp is used.
Signed-off-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
[mpe: Move subdir-ccflags in xmon/Makefile to not clobber -Werror]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

The "count < sizeof(struct os_area_db)" comparison is type promoted to
size_t so negative values of "count" are treated as very high values
and we accidentally return success instead of a negative error code.

This doesn't really change runtime much but it fixes a static checker
warning.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Geoff Levand <geoff@infradead.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

On a Power9 box we get a few screens full of these on boot. Drop
them to pr_debug.

  [    5.993645] nest_centaur6_imc performance monitor hardware support registered
  [    5.993728] nest_centaur7_imc performance monitor hardware support registered
  [    5.996510] core_imc performance monitor hardware support registered
  [    5.996569] nest_mba0_imc performance monitor hardware support registered
  [    5.996631] nest_mba1_imc performance monitor hardware support registered
  [    5.996685] nest_mba2_imc performance monitor hardware support registered
Signed-off-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Reviewed-by: Stewart Smith <stewart@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

instructions_to_print var is assigned value 16 and there is no
way to change it.

This patch replaces it by a constant.
Reviewed-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

When two processes crash at the same time, we sometimes encounter
interleaving in the middle of a line:

  init[1]: segfault (11) at 0 nip 0 lr 0 code 1
  init[1]: code: XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
  init[74]: segfault (11) at 10a74 nip 1000c198 lr 100078c8 code 1 in sh[10000000+14000]
  XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
  init[1]: code: XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
  init[74]: code: 90010024 bf61000c 91490a7c 3fa01002 3be00000 7d3e4b78 3bbd0c20 3b600000
  init[74]: code: 3b9d0040 7c7fe02e 2f830000 419e0028 <89230000> 2f890000 41be001c 4b7f6e79

This patch fixes it by preparing complete lines in a buffer and
printing it at once.

Fixes: 88b0fe17 ("powerpc: Add show_user_instructions()")
Reviewed-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
[mpe: Use seq_buf_printf() not seq_buf_puts() which doesn't NULL terminate]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

As spotted by sparse:

  arch/powerpc/kernel/process.c:1302:6: warning: symbol 'show_user_instructions' was not declared. Should it be static?

Fixes: 88b0fe17 ("powerpc: Add show_user_instructions()")
Reviewed-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
[mpe: Split out of larger patch]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

This patch fixes the following warnings, which are leftovers
from when __get_user() was replaced by probe_kernel_address().

arch/powerpc/kernel/process.c:1287:22: warning: incorrect type in argument 2 (different address spaces)
arch/powerpc/kernel/process.c:1287:22:    expected void const *src
arch/powerpc/kernel/process.c:1287:22:    got unsigned int [noderef] <asn:1>*<noident>
arch/powerpc/kernel/process.c:1319:21: warning: incorrect type in argument 2 (different address spaces)
arch/powerpc/kernel/process.c:1319:21:    expected void const *src
arch/powerpc/kernel/process.c:1319:21:    got unsigned int [noderef] <asn:1>*<noident>

Fixes: 7b051f66 ("powerpc: Use probe_kernel_address in show_instructions")
Reviewed-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
[mpe: Split out of larger patch]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

commit 06ec27ae ("powerpc/64: add stack protector support")
doesn't initialise the stack canary on SMP secondary CPU's paca,
leading to the following false positive report from the
stack protector.

smp: Bringing up secondary CPUs ...
Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: __schedule+0x978/0xa80
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.19.0-rc7-next-20181010-autotest-autotest #1
Call Trace:
[c000001fed5b3bf0] [c000000000a0ef3c] dump_stack+0xb0/0xf4 (unreliable)
[c000001fed5b3c30] [c0000000000f9d68] panic+0x140/0x308
[c000001fed5b3cc0] [c0000000000f9844] __stack_chk_fail+0x24/0x30
[c000001fed5b3d20] [c000000000a2c3a8] __schedule+0x978/0xa80
[c000001fed5b3e00] [c000000000a2c9b4] schedule_idle+0x34/0x60
[c000001fed5b3e30] [c00000000013d344] do_idle+0x224/0x3d0
[c000001fed5b3ec0] [c00000000013d6e0] cpu_startup_entry+0x30/0x50
[c000001fed5b3ef0] [c000000000047f34] start_secondary+0x4d4/0x520
[c000001fed5b3f90] [c00000000000b370] start_secondary_prolog+0x10/0x14

This patch properly initialises the stack_canary of the secondary
idle tasks.
Reported-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Fixes: 06ec27ae ("powerpc/64: add stack protector support")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Merge our fixes branch. It has a few important fixes that are needed for
futher testing and also some commits that will conflict with content in
next.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Add missing severity level to log messages.
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Modifying the request queue or changing the current state requires
mutual exclusion. Use local_irq_disable() consistently for this
rather than disabling the ADB interrupt. This simplifies the locking
scheme and brings via-macii into line with the other ADB drivers.
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

The BUG_ON assertions I added to the via-macii driver over a decade ago
haven't fired AFAIK. Some can never fire (by inspection). One assertion
checks for a NULL pointer, but that would merely substitute a BUG crash
for an Oops crash. Remove the pointless BUG_ON assertions and replace
the others with a WARN_ON and an array bounds check.
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Make the reset operation synchronous, like the other ADB drivers.
The reset request is static data but callers may not know that.
This way the struct is not in use when the reset method returns.
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Avoid the KERN_CONT problem by avoiding message fragments. The problem
arises during async ADB bus probing, when ADB messages may get mixed up
with other messages. See also, commit 4bcc595c ("printk: reinstate
KERN_CONT for printing continuation lines").

Remove a number of printk() continuation lines by logging handler
changes in adb_try_handler_change() instead.

This patch addresses the problematic use of "\n" at the beginning of
pr_cont() messages, which got overlooked in commit f2be6295
("macintosh/adb: Properly mark continued kernel messages").

That commit also changed printk(KERN_DEBUG ...) to pr_debug(...), which
hinders work on low-level ADB driver bugs. Revert that change.

Cc: Andreas Schwab <schwab@linux-m68k.org>
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Now that the 68k Mac port has adopted the via-pmu driver, the same RTC
code can be shared between m68k and powerpc. Replace duplicated code in
arch/powerpc and arch/m68k with common RTC accessors for Cuda and PMU.

Drop the problematic WARN_ON which was introduced in commit 22db552b
("powerpc/powermac: Fix rtc read/write functions").
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

With commit 2ea62630 ("powerpc/topology: Get topology for shared
processors at boot"), kdump kernel on shared LPAR may crash.

The necessary conditions are
- Shared LPAR with at least 2 nodes having memory and CPUs.
- Memory requirement for kdump kernel must be met by the first N-1
  nodes where there are at least N nodes with memory and CPUs.

Example numactl of such a machine.
  $ numactl -H
  available: 5 nodes (0,2,5-7)
  node 0 cpus:
  node 0 size: 0 MB
  node 0 free: 0 MB
  node 2 cpus:
  node 2 size: 255 MB
  node 2 free: 189 MB
  node 5 cpus: 24 25 26 27 28 29 30 31
  node 5 size: 4095 MB
  node 5 free: 4024 MB
  node 6 cpus: 0 1 2 3 4 5 6 7 16 17 18 19 20 21 22 23
  node 6 size: 6353 MB
  node 6 free: 5998 MB
  node 7 cpus: 8 9 10 11 12 13 14 15 32 33 34 35 36 37 38 39
  node 7 size: 7640 MB
  node 7 free: 7164 MB
  node distances:
  node   0   2   5   6   7
    0:  10  40  40  40  40
    2:  40  10  40  40  40
    5:  40  40  10  40  40
    6:  40  40  40  10  20
    7:  40  40  40  20  10

Steps to reproduce.
1. Load / start kdump service.
2. Trigger a kdump (for example : echo c > /proc/sysrq-trigger)

When booting a kdump kernel with 2048M:

  kexec: Starting switchover sequence.
  I'm in purgatory
  Using 1TB segments
  hash-mmu: Initializing hash mmu with SLB
  Linux version 4.19.0-rc5-master+ (srikar@linux-xxu6) (gcc version 4.8.5 (SUSE Linux)) #1 SMP Thu Sep 27 19:45:00 IST 2018
  Found initrd at 0xc000000009e70000:0xc00000000ae554b4
  Using pSeries machine description
  -----------------------------------------------------
  ppc64_pft_size    = 0x1e
  phys_mem_size     = 0x88000000
  dcache_bsize      = 0x80
  icache_bsize      = 0x80
  cpu_features      = 0x000000ff8f5d91a7
    possible        = 0x0000fbffcf5fb1a7
    always          = 0x0000006f8b5c91a1
  cpu_user_features = 0xdc0065c2 0xef000000
  mmu_features      = 0x7c006001
  firmware_features = 0x00000007c45bfc57
  htab_hash_mask    = 0x7fffff
  physical_start    = 0x8000000
  -----------------------------------------------------
  numa:   NODE_DATA [mem 0x87d5e300-0x87d67fff]
  numa:     NODE_DATA(0) on node 6
  numa:   NODE_DATA [mem 0x87d54600-0x87d5e2ff]
  Top of RAM: 0x88000000, Total RAM: 0x88000000
  Memory hole size: 0MB
  Zone ranges:
    DMA      [mem 0x0000000000000000-0x0000000087ffffff]
    DMA32    empty
    Normal   empty
  Movable zone start for each node
  Early memory node ranges
    node   6: [mem 0x0000000000000000-0x0000000087ffffff]
  Could not find start_pfn for node 0
  Initmem setup node 0 [mem 0x0000000000000000-0x0000000000000000]
  On node 0 totalpages: 0
  Initmem setup node 6 [mem 0x0000000000000000-0x0000000087ffffff]
  On node 6 totalpages: 34816

  Unable to handle kernel paging request for data at address 0x00000060
  Faulting instruction address: 0xc000000008703a54
  Oops: Kernel access of bad area, sig: 11 [#1]
  LE SMP NR_CPUS=2048 NUMA pSeries
  Modules linked in:
  CPU: 11 PID: 1 Comm: swapper/11 Not tainted 4.19.0-rc5-master+ #1
  NIP:  c000000008703a54 LR: c000000008703a38 CTR: 0000000000000000
  REGS: c00000000b673440 TRAP: 0380   Not tainted  (4.19.0-rc5-master+)
  MSR:  8000000002009033 <SF,VEC,EE,ME,IR,DR,RI,LE>  CR: 24022022  XER: 20000002
  CFAR: c0000000086fc238 IRQMASK: 0
  GPR00: c000000008703a38 c00000000b6736c0 c000000009281900 0000000000000000
  GPR04: 0000000000000000 0000000000000000 fffffffffffff001 c00000000b660080
  GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000220
  GPR12: 0000000000002200 c000000009e51400 0000000000000000 0000000000000008
  GPR16: 0000000000000000 c000000008c152e8 c000000008c152a8 0000000000000000
  GPR20: c000000009422fd8 c000000009412fd8 c000000009426040 0000000000000008
  GPR24: 0000000000000000 0000000000000000 c000000009168bc8 c000000009168c78
  GPR28: c00000000b126410 0000000000000000 c00000000916a0b8 c00000000b126400
  NIP [c000000008703a54] bus_add_device+0x84/0x1e0
  LR [c000000008703a38] bus_add_device+0x68/0x1e0
  Call Trace:
  [c00000000b6736c0] [c000000008703a38] bus_add_device+0x68/0x1e0 (unreliable)
  [c00000000b673740] [c000000008700194] device_add+0x454/0x7c0
  [c00000000b673800] [c00000000872e660] __register_one_node+0xb0/0x240
  [c00000000b673860] [c00000000839a6bc] __try_online_node+0x12c/0x180
  [c00000000b673900] [c00000000839b978] try_online_node+0x58/0x90
  [c00000000b673930] [c0000000080846d8] find_and_online_cpu_nid+0x158/0x190
  [c00000000b673a10] [c0000000080848a0] numa_update_cpu_topology+0x190/0x580
  [c00000000b673c00] [c000000008d3f2e4] smp_cpus_done+0x94/0x108
  [c00000000b673c70] [c000000008d5c00c] smp_init+0x174/0x19c
  [c00000000b673d00] [c000000008d346b8] kernel_init_freeable+0x1e0/0x450
  [c00000000b673dc0] [c0000000080102e8] kernel_init+0x28/0x160
  [c00000000b673e30] [c00000000800b65c] ret_from_kernel_thread+0x5c/0x80
  Instruction dump:
  60000000 60000000 e89e0020 7fe3fb78 4bff87d5 60000000 7c7d1b79 4082008c
  e8bf0050 e93e0098 3b9f0010 2fa50000 <e8690060> 38630018 419e0114 7f84e378
  ---[ end trace 593577668c2daa65 ]---

However a regular kernel with 4096M (2048 gets reserved for crash
kernel) boots properly.

Unlike regular kernels, which mark all available nodes as online,
kdump kernel only marks just enough nodes as online and marks the rest
as offline at boot. However kdump kernel boots with all available
CPUs. With Commit 2ea62630 ("powerpc/topology: Get topology for
shared processors at boot"), all CPUs are onlined on their respective
nodes at boot time. try_online_node() tries to online the offline
nodes but fails as all needed subsystems are not yet initialized.

As part of fix, detect and skip early onlining of a offline node.

Fixes: 2ea62630 ("powerpc/topology: Get topology for shared processors at boot")
Reported-by: Pavithra Prakash <pavrampu@in.ibm.com>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Tested-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>