linux-stable.git/arch/powerpc/kernel/rtas.c, branch linux-5.2.y

powerpc/rtas: use device model APIs and serialization during LPM

2019-10-07T16:59:09+00:00

[ Upstream commit a6717c01ddc259f6f73364779df058e2c67309f8 ]

The LPAR migration implementation and userspace-initiated cpu hotplug
can interleave their executions like so:

1. Set cpu 7 offline via sysfs.

2. Begin a partition migration, whose implementation requires the OS
   to ensure all present cpus are online; cpu 7 is onlined:

     rtas_ibm_suspend_me -> rtas_online_cpus_mask -> cpu_up

   This sets cpu 7 online in all respects except for the cpu's
   corresponding struct device; dev->offline remains true.

3. Set cpu 7 online via sysfs. _cpu_up() determines that cpu 7 is
   already online and returns success. The driver core (device_online)
   sets dev->offline = false.

4. The migration completes and restores cpu 7 to offline state:

     rtas_ibm_suspend_me -> rtas_offline_cpus_mask -> cpu_down

This leaves cpu7 in a state where the driver core considers the cpu
device online, but in all other respects it is offline and
unused. Attempts to online the cpu via sysfs appear to succeed but the
driver core actually does not pass the request to the lower-level
cpuhp support code. This makes the cpu unusable until the cpu device
is manually set offline and then online again via sysfs.

Instead of directly calling cpu_up/cpu_down, the migration code should
use the higher-level device core APIs to maintain consistent state and
serialize operations.

Fixes: 120496ac2d2d ("powerpc: Bring all threads online prior to migration/hibernation")
Signed-off-by: Nathan Lynch 
Reviewed-by: Gautham R. Shenoy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20190802192926.19277-2-nathanl@linux.ibm.com
Signed-off-by: Sasha Levin

powerpc/rtas: retry when cpu offline races with suspend/migration

2019-07-31T05:24:44+00:00

[ Upstream commit 9fb603050ffd94f8127df99c699cca2f575eb6a0 ]

The protocol for suspending or migrating an LPAR requires all present
processor threads to enter H_JOIN. So if we have threads offline, we
have to temporarily bring them up. This can race with administrator
actions such as SMT state changes. As of dfd718a2ed1f ("powerpc/rtas:
Fix a potential race between CPU-Offline & Migration"),
rtas_ibm_suspend_me() accounts for this, but errors out with -EBUSY
for what almost certainly is a transient condition in any reasonable
scenario.

Callers of rtas_ibm_suspend_me() already retry when -EAGAIN is
returned, and it is typical during a migration for that to happen
repeatedly for several minutes polling the H_VASI_STATE hcall result
before proceeding to the next stage.

So return -EAGAIN instead of -EBUSY when this race is
encountered. Additionally: logging this event is still appropriate but
use pr_info instead of pr_err; and remove use of unlikely() while here
as this is not a hot path at all.

Fixes: dfd718a2ed1f ("powerpc/rtas: Fix a potential race between CPU-Offline & Migration")
Signed-off-by: Nathan Lynch 
Signed-off-by: Michael Ellerman 
Signed-off-by: Sasha Levin

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

2019-05-30T18:26:32+00:00

Based on 1 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license as published by
  the free software foundation either version 2 of the license or at
  your option any later version

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 3029 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Allison Randal 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de
Signed-off-by: Greg Kroah-Hartman

memblock: drop memblock_alloc_base()

2019-03-12T17:04:01+00:00

The memblock_alloc_base() function tries to allocate a memory up to the
limit specified by its max_addr parameter and panics if the allocation
fails.  Replace its usage with memblock_phys_alloc_range() and make the
callers check the return value and panic in case of error.

Link: http://lkml.kernel.org/r/1548057848-15136-10-git-send-email-rppt@linux.ibm.com
Signed-off-by: Mike Rapoport 
Acked-by: Michael Ellerman 		[powerpc]
Cc: Catalin Marinas 
Cc: Christophe Leroy 
Cc: Christoph Hellwig 
Cc: "David S. Miller" 
Cc: Dennis Zhou 
Cc: Geert Uytterhoeven 
Cc: Greentime Hu 
Cc: Greg Kroah-Hartman 
Cc: Guan Xuetao 
Cc: Guo Ren 
Cc: Guo Ren 				[c-sky]
Cc: Heiko Carstens 
Cc: Juergen Gross 			[Xen]
Cc: Mark Salter 
Cc: Matt Turner 
Cc: Max Filippov 
Cc: Michael Ellerman 
Cc: Michal Simek 
Cc: Paul Burton 
Cc: Petr Mladek 
Cc: Richard Weinberger 
Cc: Rich Felker 
Cc: Rob Herring 
Cc: Rob Herring 
Cc: Russell King 
Cc: Stafford Horne 
Cc: Tony Luck 
Cc: Vineet Gupta 
Cc: Yoshinori Sato 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

powerpc/rtas: Fix a potential race between CPU-Offline & Migration

2018-10-13T11:21:25+00:00

Live Partition Migrations require all the present CPUs to execute the
H_JOIN call, and hence rtas_ibm_suspend_me() onlines any offline CPUs
before initiating the migration for this purpose.

The commit 85a88cabad57
("powerpc/pseries: Disable CPU hotplug across migrations")
disables any CPU-hotplug operations once all the offline CPUs are
brought online to prevent any further state change. Once the
CPU-Hotplug operation is disabled, the code assumes that all the CPUs
are online.

However, there is a minor window in rtas_ibm_suspend_me() between
onlining the offline CPUs and disabling CPU-Hotplug when a concurrent
CPU-offline operations initiated by the userspace can succeed thereby
nullifying the the aformentioned assumption. In this unlikely case
these offlined CPUs will not call H_JOIN, resulting in a system hang.

Fix this by verifying that all the present CPUs are actually online
after CPU-Hotplug has been disabled, failing which we restore the
state of the offline CPUs in rtas_ibm_suspend_me() and return an
-EBUSY.

Cc: Nathan Fontenot 
Cc: Tyrel Datwyler 
Suggested-by: Michael Ellerman 
Signed-off-by: Gautham R. Shenoy 
Reviewed-by: Nathan Fontenot 
Signed-off-by: Michael Ellerman

powerpc/pseries/mobility: Extend start/stop topology update scope

2018-10-13T11:21:25+00:00

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 
Reviewed-by: Nathan Fontenot 
Signed-off-by: Michael Ellerman

powerpc/pseries: Disable CPU hotplug across migrations

2018-09-19T12:08:12+00:00

When performing partition migrations all present CPUs must be online
as all present CPUs must make the H_JOIN call as part of the migration
process. Once all present CPUs make the H_JOIN call, one CPU is returned
to make the rtas call to perform the migration to the destination system.

During testing of migration and changing the SMT state we have found
instances where CPUs are offlined, as part of the SMT state change,
before they make the H_JOIN call. This results in a hung system where
every CPU is either in H_JOIN or offline.

To prevent this this patch disables CPU hotplug during the migration
process.

Signed-off-by: Nathan Fontenot 
Reviewed-by: Tyrel Datwyler 
Signed-off-by: Michael Ellerman

powerpc: Remove -Wattribute-alias pragmas

2018-06-25T14:21:13+00:00

With SYSCALL_DEFINEx() disabling -Wattribute-alias generically, there's
no need to duplicate that for PowerPC syscalls.

This reverts commit 415520373975 ("powerpc: fix build failure by
disabling attribute-alias warning in pci_32") and commit 2479bfc9bc60
("powerpc: Fix build by disabling attribute-alias warning for
SYSCALL_DEFINEx").

Signed-off-by: Paul Burton 
Acked-by: Christophe Leroy 
Acked-by: Michael Ellerman 
Signed-off-by: Masahiro Yamada

powerpc: Fix build by disabling attribute-alias warning for SYSCALL_DEFINEx

2018-06-03T10:40:24+00:00

GCC 8.1 emits warnings such as the following. As arch/powerpc code is
built with -Werror, this breaks the build with GCC 8.1.

  In file included from arch/powerpc/kernel/pci_64.c:23:
  ./include/linux/syscalls.h:233:18: error: 'sys_pciconfig_iobase' alias
  between functions of incompatible types 'long int(long int, long
  unsigned int, long unsigned int)' and 'long int(long int, long int,
  long int)' [-Werror=attribute-alias]
    asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
                    ^~~
  ./include/linux/syscalls.h:222:2: note: in expansion of macro '__SYSCALL_DEFINEx'
    __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)

This patch inhibits those warnings.

Signed-off-by: Christophe Leroy 
[mpe: Trim change log]
Signed-off-by: Michael Ellerman

powerpc/syscalls: switch rtas(2) to SYSCALL_DEFINE

2018-05-10T13:25:14+00:00

Signed-off-by: Al Viro 
[mpe: Update sys_ni.c for s/ppc_rtas/sys_rtas/]
Signed-off-by: Michael Ellerman