On 26/10/2016 13:35, 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");
> +}
> +
> +static inline void wrmsr_notrace(unsigned msr, unsigned low, unsigned high)
> +{
> + native_write_msr_notrace(msr, low, high);
> +}
> +
> +/* Can be uninlined because referenced by paravirt */
> notrace static inline int native_write_msr_safe(unsigned int msr,
> unsigned low, unsigned high)
> {
> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
> index 88c657b..2686894 100644
> --- a/arch/x86/kernel/apic/apic.c
> +++ b/arch/x86/kernel/apic/apic.c
> @@ -2263,6 +2263,7 @@ void __init apic_set_eoi_write(void (*eoi_write)(u32
> reg, u32 v))
> for (drv = __apicdrivers; drv < __apicdrivers_end; drv++) {
> /* Should happen once for each apic */
> WARN_ON((*drv)->eoi_write == eoi_write);
> + (*drv)->native_eoi_write = (*drv)->eoi_write;
> (*drv)->eoi_write = eoi_write;
> }
> }
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index edbbfc8..d230513 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -308,7 +308,7 @@ static void kvm_register_steal_time(void)
>
> static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
>
> -static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
> +notrace static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
> {
> /**
> * This relies on __test_and_clear_bit to modify the memory
> @@ -319,7 +319,7 @@ static void kvm_guest_apic_eoi_write(u32 reg, u32 val)
> */
> if (__test_and_clear_bit(KVM_PV_EOI_BIT, this_cpu_ptr(&kvm_apic_eoi)))
> return;
> - apic_write(APIC_EOI, APIC_EOI_ACK);
> + apic->native_eoi_write(APIC_EOI, APIC_EOI_ACK);
> }
>
> static void kvm_guest_cpu_init(void)
> diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
> index c00cb64..68f8cc2 100644
> --- a/arch/x86/kernel/smp.c
> +++ b/arch/x86/kernel/smp.c
> @@ -261,10 +261,8 @@ static inline void __smp_reschedule_interrupt(void)
>
> __visible void smp_reschedule_interrupt(struct pt_regs *regs)
> {
> - irq_enter();
> ack_APIC_irq();
> __smp_reschedule_interrupt();
> - irq_exit();
> /*
> * KVM uses this interrupt to force a cpu out of guest mode
> */
>
Acked-by: Paolo Bonzini <pbonz...@redhat.com>
