On Wed, Oct 26, 2016 at 07:35:26PM +0800, Wanpeng Li wrote:
> From: Wanpeng Li <wanpeng...@hotmail.com>
>
> As Peterz pointed out:
>
> | The thing is, many many smp_reschedule_interrupt() invocations don't
> | actually execute anything much at all and are only send to tickle the
> | return to user path (which does the actual preemption).
>
> This patch add write msr notrace to avoid the debug codes splash.
>
> Suggested-by: Peter Zijlstra <pet...@infradead.org>
> Suggested-by: Paolo Bonzini <pbonz...@redhat.com>
> Cc: Ingo Molnar <mi...@kernel.org>
> Cc: Mike Galbraith <efa...@gmx.de>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: Paolo Bonzini <pbonz...@redhat.com>
> Signed-off-by: Wanpeng Li <wanpeng...@hotmail.com>
> ---
> arch/x86/include/asm/apic.h | 3 ++-
> arch/x86/include/asm/msr.h | 15 +++++++++++++++
> arch/x86/kernel/apic/apic.c | 1 +
> arch/x86/kernel/kvm.c | 4 ++--
> arch/x86/kernel/smp.c | 2 --
> 5 files changed, 20 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
> index f5aaf6c..a5a0bcf 100644
> --- a/arch/x86/include/asm/apic.h
> +++ b/arch/x86/include/asm/apic.h
> @@ -196,7 +196,7 @@ static inline void native_apic_msr_write(u32 reg, u32 v)
>
> static inline void native_apic_msr_eoi_write(u32 reg, u32 v)
> {
> - wrmsr(APIC_BASE_MSR + (APIC_EOI >> 4), APIC_EOI_ACK, 0);
> + wrmsr_notrace(APIC_BASE_MSR + (APIC_EOI >> 4), APIC_EOI_ACK, 0);
> }
>
> static inline u32 native_apic_msr_read(u32 reg)
> @@ -332,6 +332,7 @@ struct apic {
> * on write for EOI.
> */
> void (*eoi_write)(u32 reg, u32 v);
> + void (*native_eoi_write)(u32 reg, u32 v);
> u64 (*icr_read)(void);
> void (*icr_write)(u32 low, u32 high);
> void (*wait_icr_idle)(void);
> diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
> index b5fee97..afbb221 100644
> --- a/arch/x86/include/asm/msr.h
> +++ b/arch/x86/include/asm/msr.h
> @@ -127,6 +127,21 @@ notrace static inline void native_write_msr(unsigned int
> msr,
> }
>
> /* Can be uninlined because referenced by paravirt */
> +notrace static inline void native_write_msr_notrace(unsigned int msr,
> + unsigned low, unsigned high)
> +{
> + asm volatile("1: wrmsr\n"
> + "2:\n"
> + _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_wrmsr_unsafe)
> + : : "c" (msr), "a"(low), "d" (high) : "memory");
> +}
Why is this duplicating the inline asm?
This function should be called __native_write_msr_notrace() instead and
then native_write_msr() should do:
notrace static inline void native_write_msr(unsigned int msr,
unsigned low, unsigned high)
{
__native_write_msr_notrace(msr, low, high);
if (msr_tracepoint_active(__tracepoint_write_msr))
do_trace_write_msr(msr, ((u64)high << 32 | low), 0);
}
This way it is way more clear who calls what.
And this thing should be two patches anyway:
1. change native_write_msr()
2. Add the apic changes.
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
