On Sun, May 29, 2016 at 10:03:50PM +1000, Anton Blanchard wrote:
> From: Anton Blanchard <an...@samba.org>
>
> In both __giveup_fpu() and __giveup_altivec() we make two modifications
> to tsk->thread.regs->msr. gcc decides to do a read/modify/write of
> each change, so we end up with a load hit store:
>
> ld r9,264(r10)
> rldicl r9,r9,50,1
> rotldi r9,r9,14
> std r9,264(r10)
> ...
> ld r9,264(r10)
> rldicl r9,r9,40,1
> rotldi r9,r9,24
> std r9,264(r10)
>
> Fix this by using a temporary.
>
> Signed-off-by: Anton Blanchard <an...@samba.org>
> ---
> arch/powerpc/kernel/process.c | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index e2f12cb..7da1f92 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -139,12 +139,16 @@ EXPORT_SYMBOL(__msr_check_and_clear);
> #ifdef CONFIG_PPC_FPU
> void __giveup_fpu(struct task_struct *tsk)
> {
> + u64 msr;
Huh? Make it an unsigned long please, which is the type of the msr
field in struct pt_regs to work on both 32 and 64 bit processors.
> +
> save_fpu(tsk);
> - tsk->thread.regs->msr &= ~MSR_FP;
> + msr = tsk->thread.regs->msr;
> + msr &= ~MSR_FP;
> #ifdef CONFIG_VSX
> if (cpu_has_feature(CPU_FTR_VSX))
> - tsk->thread.regs->msr &= ~MSR_VSX;
> + msr &= ~MSR_VSX;
> #endif
> + tsk->thread.regs->msr = msr;
> }
>
> void giveup_fpu(struct task_struct *tsk)
> @@ -219,12 +223,16 @@ static int restore_fp(struct task_struct *tsk) { return
> 0; }
>
> static void __giveup_altivec(struct task_struct *tsk)
> {
> + u64 msr;
> +
Ditto.
> save_altivec(tsk);
> - tsk->thread.regs->msr &= ~MSR_VEC;
> + msr = tsk->thread.regs->msr;
> + msr &= ~MSR_VEC;
> #ifdef CONFIG_VSX
> if (cpu_has_feature(CPU_FTR_VSX))
> - tsk->thread.regs->msr &= ~MSR_VSX;
> + msr &= ~MSR_VSX;
> #endif
> + tsk->thread.regs->msr = msr;
> }
>
> void giveup_altivec(struct task_struct *tsk)
> --
> 2.7.4
>
Gabriel
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