Messages in this thread Patch in this message | | | From | Wanpeng Li <> | Subject | [PATCH v3] x86/msr: Add write msr notrace to avoid the debug codes splash | Date | Tue, 25 Oct 2016 10:58:05 +0800 |
| |
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 <peterz@infradead.org> Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Wanpeng Li <wanpeng.li@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 | 2 +- arch/x86/kernel/smp.c | 2 -- 5 files changed, 19 insertions(+), 4 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..ca9eef7 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -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 */ -- 1.9.1
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