Subject: Re: powerpc: set used_vsr/used_vr/used_spe in sigreturn path when MSR bits are active

From: Michael Ellerman <[email-masked]>
Date: Tue, 13 Sep 2016 22:16:38 +1000 (AEST)

On Tue, 2016-26-07 at 08:06:01 UTC, Simon Guo wrote:
> From: Simon Guo <[email-masked]>
> 
> Normally, when MSR[VSX/VR/SPE] bits = 1, the used_vsr/used_vr/used_spe
> bit have already been set. However signal frame locates at user space
> and it is controlled by user application. It is up to kernel to make
> sure used_vsr/used_vr/used_spe(in kernel)=1 and consistent with MSR
> bits.
> 
> For example, CRIU application, who utilizes sigreturn to restore
> checkpointed process, will lead to the case where MSR[VSX] bit is
> active in signal frame, but used_vsx bit is not set. (the same applies
> to VR/SPE).
> 
> This patch will reinforce this at kernel by always setting used_* bit
> when MSR related bits are active in signal frame and we are doing
> sigreturn.
> 
> This patch is based on Ben's Proposal.
> 
> Signed-off-by: Benjamin Herrenschmidt <[email-masked]>
> Signed-off-by: Simon Guo <[email-masked]>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/e1c0d66fcb179a1737b3d5cc11

cheers