2016-10-26 19:50 GMT+08:00 Borislav Petkov <b...@alien8.de>:
> 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.
Thanks for pointing out.
Regards,
Wanpeng Li
