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KVM: x86: Check for nested events if there is an injectable interrupt 

With commit b6b8a1451f 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 <bsd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Bandan Das 2014-07-08 00:30:23 -04:00 committed by Paolo Bonzini
parent cd3de83f14
commit 9242b5b60d
1 changed files with 12 additions and 0 deletions
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12
arch/x86/kvm/x86.c
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@ -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);