From 8ca225520e278e41396dab0524989f4848626f83 Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Mon, 7 Nov 2016 11:13:40 +0800 Subject: x86/apic: Prevent tracing on apic_msr_write_eoi() The following RCU lockdep warning led to adding irq_enter()/irq_exit() into smp_reschedule_interrupt(): RCU used illegally from idle CPU! rcu_scheduler_active = 1, debug_locks = 0 RCU used illegally from extended quiescent state! no locks held by swapper/1/0. do_trace_write_msr native_write_msr native_apic_msr_eoi_write smp_reschedule_interrupt reschedule_interrupt As Peterz pointed out: | So now we're making a very frequent interrupt slower because of debug | code. | | The thing is, many many smp_reschedule_interrupt() invocations don't | actually execute anything much at all and are only sent to tickle the | return to user path (which does the actual preemption). | | Having to do the whole irq_enter/irq_exit dance just for this unlikely | debug case totally blows. Use the wrmsr_notrace() variant in native_apic_msr_write_eoi, annotate the kvm variant with notrace and add a native_apic_eoi callback to the apic structure so KVM guests are covered as well. This allows to revert the irq_enter/irq_exit dance in smp_reschedule_interrupt(). Suggested-by: Peter Zijlstra Suggested-by: Paolo Bonzini Signed-off-by: Wanpeng Li Acked-by: Paolo Bonzini Cc: kvm@vger.kernel.org Cc: Mike Galbraith Cc: Borislav Petkov Link: http://lkml.kernel.org/r/1478488420-5982-3-git-send-email-wanpeng.li@hotmail.com Signed-off-by: Thomas Gleixner --- arch/x86/kernel/smp.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'arch/x86/kernel/smp.c') diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c index c00cb64bc0a1..68f8cc222f25 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 */ -- cgit 1.4.1