ACK: [SRU][F][G][H] [PATCH 0/2] Fix misalignment buffer on Power9 DD2.1 (LP: 1902694)

[Kleber Souza]

On 04.11.20 06:27, patricia.domingues at canonical.com wrote:
> BugLink: https://bugs.launchpad.net/bugs/1902694
> 
> SRU Justification:
> 
> [Impact]
> 
> * A data integrity issue was observed on POWER 9 (DD2.1) systems.
> 
> * It affects Ubuntu 20.04 with kernel 5.4.0-52 and Ubuntu 20.10 with kernel 5.8.0-26 kernel.
> 
> * The root cause is found in the compiling of p9_hmi_special_emu().
> 
> * When doing a VMX store (in __get_user_atomic_128_aligned()) to a buffer (vbuf), the buffer is not 128 bit aligned.
> 
> [Fix]
> 
> * 1da4a0272c54 "powerpc: Fix undetected data corruption with P9N DD2.1 VSX CI load emulation"
> 
> * d1781f237047 "selftests/powerpc: Make alignment handler test P9N DD2.1 vector CI load workaround"
> 
> [Test Case]
> 
> * A POWER 9 (DD2.1) bare metal system is needed that has either Ubuntu 20.04, 20.10 or 21.04 installed.
> 
> * It's best to test this based on a sample application and test case
>    "selftests/powerpc: Make alignment handler test P9N DD2.1 vector CI load workaround"
> 
> [Regression Potential]
> 
> * The regression risk is relatively moderate, because:
> 
> * it only happens with special VSX (vector) instructions in use, e.g. in p9_hmi_special_emu
> 
> * it happens on bare metal only and only on POWER 9 (DD2.1)
> 
> * and the changes are very overseeable (in total one effective code line per patch/commit)
> 
> * Since only p9_hmi_special_emu is touched, this will break in case of any regressions, but this is already broken based on this bug.
> 
> [Other]
> 
> * According to the reporter this affects Ubuntu 20.04 / 5.4.0-52 and 20.10 / 5.8.0-26.
> 
> * Since the development of Hirsute is already open the SRU is requested for Hirsute, too.
> 
> * Patches got upstream accepted in v5.10-rc1 and v5.10-rc2.
> 
> Michael Neuling (2):
>    powerpc: Fix undetected data corruption with P9N DD2.1 VSX CI load
>      emulation
>    selftests/powerpc: Make alignment handler test P9N DD2.1 vector CI
>      load workaround
> 
>   arch/powerpc/kernel/traps.c                               | 2 +-
>   .../selftests/powerpc/alignment/alignment_handler.c       | 8 ++++++--
>   2 files changed, 7 insertions(+), 3 deletions(-)
> 


Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>