x86/apic: Prevent tracing on apic_msr_write_eoi()
authorWanpeng Li <wanpeng.li@hotmail.com>
Mon, 7 Nov 2016 03:13:40 +0000 (11:13 +0800)
committerThomas Gleixner <tglx@linutronix.de>
Wed, 9 Nov 2016 21:03:14 +0000 (22:03 +0100)
commit8ca225520e278e41396dab0524989f4848626f83
treec71f406bb7dc56ef41e7043672b5842593998f09
parentb2c5ea4f759190ee9f75687a00035c1a66d0d743
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 <peterz@infradead.org>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org
Cc: Mike Galbraith <efault@gmx.de>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/1478488420-5982-3-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
arch/x86/include/asm/apic.h
arch/x86/kernel/apic/apic.c
arch/x86/kernel/kvm.c
arch/x86/kernel/smp.c