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authorBandan Das <bsd@redhat.com>2014-07-08 00:30:23 -0400
committerPaolo Bonzini <pbonzini@redhat.com>2014-07-08 10:06:42 +0200
commit9242b5b60df8b13b469bc6b7be08ff6ebb551ad3 (patch)
treec490ce887713f72c5ba0df7c214693abf7fa60f4 /arch/x86
parentcd3de83f147601356395b57a8673e9c5ff1e59d1 (diff)
downloadlinux-9242b5b60df8b13b469bc6b7be08ff6ebb551ad3.tar.bz2
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 <bsd@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/kvm/x86.c12
1 files changed, 12 insertions, 0 deletions
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);