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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>
This commit is contained in:
Wanpeng Li 2016-11-07 11:13:40 +08:00 committed by Thomas Gleixner
parent b2c5ea4f75
commit 8ca225520e
4 changed files with 5 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/x86/include/asm/apic.h
View File

@ -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);

1
arch/x86/kernel/apic/apic.c
View File

@ -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;
}
}

4
arch/x86/kernel/kvm.c
View File

@ -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)
static notrace 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)

2
arch/x86/kernel/smp.c
View File

@ -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
*/