ACK/cmnt: [SRU][Zesty][PATCH 0/4] Fixes for LP:1685792

[Colin Ian King]

On 17/05/17 11:51, Joseph Salisbury wrote:
> BugLink: http://bugs.launchpad.net/bugs/1685792
> 
> == SRU Justification ==
> Power9 DD1 has a hardware issue that when all threads are 
> offlined  and then any of the CPUs are onlined, they come online with an 
> incorrect PACA thereby resulting in a crash.
> 
> These four patches are in mainline as of v4.12-rc1.  They are needed to get 
> CPU-Hotplug working correctly on a Power9 DD1 system.
> 
> The first three patches are clean cherry picks, but the fourth required
> a minor backport.
> 
> == Fixes ==
> commit a7cd88da97040513e17cd77ae3e57764e854bae4
> Author: Gautham R. Shenoy <ego at linux.vnet.ibm.com>
> Date:   Wed Mar 22 20:34:14 2017 +0530
> 
>     powerpc/powernv: Move CPU-Offline idle state invocation from smp.c to idle.c
> 
> commit 9006123157886acc47bdc17e26c933d710b8d6cd
> Author: Gautham R. Shenoy <ego at linux.vnet.ibm.com>
> Date:   Wed Mar 22 20:34:15 2017 +0530
> 
>     powerpc/powernv/smp: Add busy-wait loop as fall back for CPU-Hotplug
> 
> commit f3b3f28493d93232a37d5fbb5cb5ad168ede0e1a
> Author: Gautham R. Shenoy <ego at linux.vnet.ibm.com>
> Date:   Wed Mar 22 20:34:16 2017 +0530
> 
>     powerpc/powernv/idle: Don't override default/deepest directly in kernel
> 
> commit 17ed4c8f81da2bf340d33a8c875f4d6b1dfd9398
> Author: Gautham R. Shenoy <ego at linux.vnet.ibm.com>
> Date:   Wed Mar 22 20:34:17 2017 +0530
> 
>     powerpc/powernv: Recover correct PACA on wakeup from a stop on P9 DD1
> 
> 
> == Test Case ==
> A test kernel was built with these patches and tested by the original bug reporter.
> The bug reporter states the test kernel resolved the bug.
> 
> Gautham R. Shenoy (4):
>   powerpc/powernv: Move CPU-Offline idle state invocation from smp.c to
>     idle.c
>   powerpc/powernv/smp: Add busy-wait loop as fall back for CPU-Hotplug
>   powerpc/powernv/idle: Don't override default/deepest directly in
>     kernel
>   powerpc/powernv: Recover correct PACA on wakeup from a stop on P9 DD1
> 
>  arch/powerpc/include/asm/cpuidle.h       |  1 +
>  arch/powerpc/include/asm/paca.h          |  5 ++
>  arch/powerpc/kernel/asm-offsets.c        |  2 +
>  arch/powerpc/kernel/idle_book3s.S        | 48 +++++++++++++++-
>  arch/powerpc/platforms/powernv/idle.c    | 96 ++++++++++++++++++++++++++------
>  arch/powerpc/platforms/powernv/powernv.h |  2 -
>  arch/powerpc/platforms/powernv/smp.c     | 18 +-----
>  7 files changed, 137 insertions(+), 35 deletions(-)
> 

Upstream patches that are clean cherry picks (and a minor backport
tweak).  Bug reporter states that these fix the issue, so testing looks
good from what I can gather. Risk limited to 1 architecture.

Comment: The original SRU bug could do with the normal SRU info in a
clearer form including data such as regression potential risk, etc.

For all 4 patches:

Acked-by: Colin Ian King <colin.king at canonical.com>