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authorGleb Natapov <gleb@redhat.com>2013-06-03 11:30:02 +0300
committerGleb Natapov <gleb@redhat.com>2013-06-03 11:32:39 +0300
commit299018f44ac553dce3caf84df1d14c4764faa279 (patch)
tree75c178b1c2767697e2bef132aea84a8c04c1b156 /arch
parent8acb42070ec4c87a9baab5c7bac626030d5bef28 (diff)
downloadvexpress-lsk-299018f44ac553dce3caf84df1d14c4764faa279.tar.gz
KVM: Fix race in apic->pending_events processing
apic->pending_events processing has a race that may cause INIT and SIPI processing to be reordered: vpu0: vcpu1: set INIT test_and_clear_bit(KVM_APIC_INIT) process INIT set INIT set SIPI test_and_clear_bit(KVM_APIC_SIPI) process SIPI At the end INIT is left pending in pending_events. The following patch fixes this by latching pending event before processing them. Signed-off-by: Gleb Natapov <gleb@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/lapic.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index e1adbb4aca7..0eee2c8b64d 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1861,11 +1861,14 @@ void kvm_apic_accept_events(struct kvm_vcpu *vcpu)
{
struct kvm_lapic *apic = vcpu->arch.apic;
unsigned int sipi_vector;
+ unsigned long pe;
- if (!kvm_vcpu_has_lapic(vcpu))
+ if (!kvm_vcpu_has_lapic(vcpu) || !apic->pending_events)
return;
- if (test_and_clear_bit(KVM_APIC_INIT, &apic->pending_events)) {
+ pe = xchg(&apic->pending_events, 0);
+
+ if (test_bit(KVM_APIC_INIT, &pe)) {
kvm_lapic_reset(vcpu);
kvm_vcpu_reset(vcpu);
if (kvm_vcpu_is_bsp(apic->vcpu))
@@ -1873,7 +1876,7 @@ void kvm_apic_accept_events(struct kvm_vcpu *vcpu)
else
vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
}
- if (test_and_clear_bit(KVM_APIC_SIPI, &apic->pending_events) &&
+ if (test_bit(KVM_APIC_SIPI, &pe) &&
vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
/* evaluate pending_events before reading the vector */
smp_rmb();