Comment 1 for bug 1669023

Leann,

Patch to fix an error caused by a typo, please have the Kernel Team
evaluate.

Thanks.

                   Michael

On 03/01/2017 07:29 AM, Launchpad Bug Tracker wrote:
> bugproxy (bugproxy) has assigned this bug to you for Ubuntu:
>
> Canonical,
>
> Please include the following fix on 16.10. This typo is causing some issue on TM.
> The patches that causes this problem is ec2a04841b785373a6379af66032201a2b90922b on yakkety-ubuntu repo.
>
> commit 39715bf972ed4fee18fe5409609a971fb16b1771
> Author: Valentin Rothberg <email address hidden>
> Date: Wed Oct 5 07:57:26 2016 +0200
>
> powerpc/process: Fix CONFIG_ALIVEC typo in restore_tm_state()
>
> It should be ALTIVEC, not ALIVEC.
>
> Cyril explains: If a thread performs a transaction with altivec and then
> gets preempted for whatever reason, this bug may cause the kernel to not
> re-enable altivec when that thread runs again. This will result in an
> altivec unavailable fault, when that fault happens inside a user
> transaction the kernel has no choice but to enable altivec and doom the
> transaction.
>
> The result is that transactions using altivec may get aborted more often
> than they should.
>
> The difficulty in catching this with a selftest is my deliberate use of
> the word may above. Optimisations to avoid FPU/altivec/VSX faults mean
> that the kernel will always leave them on for 255 switches. This code
> prevents the kernel turning it off if it got to the 256th switch (and
> userspace was transactional).
>
> Fixes: dc16b553c949 ("powerpc: Always restore FPU/VEC/VSX if hardware transactional memory in use")
> Reviewed-by: Cyril Bur <email address hidden>
> Signed-off-by: Valentin Rothberg <email address hidden>
> Signed-off-by: Michael Ellerman <email address hidden>
>
> ** Affects: ubuntu
> Importance: Undecided
> Assignee: Taco Screen team (taco-screen-team)
> Status: New
>
>
> ** Tags: architecture-ppc64le bugnameltc-152112 severity-high targetmilestone-inin1610

--
Michael Hohnbaum
OIL Program Manager
Power (ppc64el) Development Project Manager
Canonical, Ltd.