On Wed, 2016-08-17 at 13:43 +1000, Cyril Bur wrote:
> mfmsr() is a fairly expensive call and callers of msr_check_and_set()
> may want to make decisions bits in the MSR that it did not change but
> may not know the value of.
I can't grok this. Please reword.
Mikey
> This patch would avoid a two calls to mfmsr().
>
> Signed-off-by: Cyril Bur <cyril...@gmail.com>
> ---
> arch/powerpc/include/asm/reg.h | 2 +-
> arch/powerpc/kernel/process.c | 4 +++-
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/reg.h
> b/arch/powerpc/include/asm/reg.h
> index f69f40f..0a3dde9 100644
> --- a/arch/powerpc/include/asm/reg.h
> +++ b/arch/powerpc/include/asm/reg.h
> @@ -1247,7 +1247,7 @@ static inline void mtmsr_isync(unsigned long val)
> : "memory")
> #endif
>
> -extern void msr_check_and_set(unsigned long bits);
> +extern unsigned long msr_check_and_set(unsigned long bits);
> extern bool strict_msr_control;
> extern void __msr_check_and_clear(unsigned long bits);
> static inline void msr_check_and_clear(unsigned long bits)
> diff --git a/arch/powerpc/kernel/process.c
> b/arch/powerpc/kernel/process.c
> index 82308fd..c42581b 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -110,7 +110,7 @@ static int __init enable_strict_msr_control(char
> *str)
> }
> early_param("ppc_strict_facility_enable", enable_strict_msr_control);
>
> -void msr_check_and_set(unsigned long bits)
> +unsigned long msr_check_and_set(unsigned long bits)
> {
> unsigned long oldmsr = mfmsr();
> unsigned long newmsr;
> @@ -124,6 +124,8 @@ void msr_check_and_set(unsigned long bits)
>
> if (oldmsr != newmsr)
> mtmsr_isync(newmsr);
> +
> + return newmsr;
> }
>
> void __msr_check_and_clear(unsigned long bits)
