From: Michael Ellerman <mpe@ellerman•id.au>
To: Oliver O'Halloran <oohall@gmail•com>, linuxppc-dev@lists•ozlabs.org
Cc: Oliver O'Halloran <oohall@gmail•com>, Anton Blanchard <anton@samba•org>
Subject: Re: powerpc/process: fix altivec SPR not being saved
Date: Thu, 31 Mar 2016 10:29:45 +1100 (AEDT) [thread overview]
Message-ID: <3qb3lF16RQz9sf6@ozlabs.org> (raw)
In-Reply-To: <1457388527-14575-1-git-send-email-oohall@gmail.com>
On Mon, 2016-07-03 at 22:08:47 UTC, Oliver O'Halloran wrote:
> In save_sprs() in process.c contains the following test:
>
> if (cpu_has_feature(cpu_has_feature(CPU_FTR_ALTIVEC)))
> t->vrsave = mfspr(SPRN_VRSAVE);
>
> CPU feature with the mask 0x1 is CPU_FTR_COHERENT_ICACHE so the test
> is equivilent to:
>
> if (cpu_has_feature(CPU_FTR_ALTIVEC) &&
> cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
>
> On CPUs without support for both (i.e G5) this results in vrsave not being
> saved between context switches. The vector register save/restore code
> doesn't use VRSAVE to determine which registers to save/restore,
> but the value of VRSAVE is used to determine if altivec is being used
> in several code paths.
>
> Signed-off-by: Oliver O'Halloran <oohall@gmail•com>
> Signed-off-by: Anton Blanchard <anton@samba•org>
> Fixes: 152d523e6307 ("powerpc: Create context switch helpers save_sprs() and restore_sprs()")
> Cc: stable@vger•kernel.org
Applied to powerpc fixes, thanks.
https://git.kernel.org/powerpc/c/01d7c2a2de47890934faba91a7
cheers
prev parent reply other threads:[~2016-03-30 23:29 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-06 22:33 [PATCH] powerpc/process: fix altivec SPR not being saved Oliver O'Halloran
2016-03-07 3:51 ` Benjamin Herrenschmidt
2016-03-07 4:19 ` Anton Blanchard
2016-03-07 22:08 ` Oliver O'Halloran
2016-03-30 23:29 ` Michael Ellerman [this message]
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