From: Bandan Das Date: Tue, 8 Jul 2014 04:30:23 +0000 (-0400) Subject: KVM: x86: Check for nested events if there is an injectable interrupt X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=9242b5b60df8b13b469bc6b7be08ff6ebb551ad3;p=deliverable%2Flinux.git KVM: x86: Check for nested events if there is an injectable interrupt With commit b6b8a1451fc40412c57d1 that introduced vmx_check_nested_events, checks for injectable interrupts happen at different points in time for L1 and L2 that could potentially cause a race. The regression occurs because KVM_REQ_EVENT is always set when nested_run_pending is set even if there's no pending interrupt. Consequently, there could be a small window when check_nested_events returns without exiting to L1, but an interrupt comes through soon after and it incorrectly, gets injected to L2 by inject_pending_event Fix this by adding a call to check for nested events too when a check for injectable interrupt returns true Signed-off-by: Bandan Das Signed-off-by: Paolo Bonzini --- diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index f6449334ec45..ef432f891d30 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5887,6 +5887,18 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool req_int_win) kvm_x86_ops->set_nmi(vcpu); } } else if (kvm_cpu_has_injectable_intr(vcpu)) { + /* + * Because interrupts can be injected asynchronously, we are + * calling check_nested_events again here to avoid a race condition. + * See https://lkml.org/lkml/2014/7/2/60 for discussion about this + * proposal and current concerns. Perhaps we should be setting + * KVM_REQ_EVENT only on certain events and not unconditionally? + */ + if (is_guest_mode(vcpu) && kvm_x86_ops->check_nested_events) { + r = kvm_x86_ops->check_nested_events(vcpu, req_int_win); + if (r != 0) + return r; + } if (kvm_x86_ops->interrupt_allowed(vcpu)) { kvm_queue_interrupt(vcpu, kvm_cpu_get_interrupt(vcpu), false);