KVM: nVMX: Ignore SIPI that arrives in L2 when vCPU is not in WFS

Fall through to handling other pending exception/events for L2 if SIPI
is pending while the CPU is not in Wait-for-SIPI.  KVM correctly ignores
the event, but incorrectly returns immediately, e.g. a SIPI coincident
with another event could lead to KVM incorrectly routing the event to L1
instead of L2.

Fixes: bf0cd88ce363 ("KVM: x86: emulate wait-for-SIPI and SIPI-VMExit")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20220830231614.3580124-11-seanjc@google.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 60e6a26..04585f5 100644 (file)
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3978,10 +3978,12 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu)
                        return -EBUSY;
 
                clear_bit(KVM_APIC_SIPI, &apic->pending_events);
-               if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED)
+               if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
                        nested_vmx_vmexit(vcpu, EXIT_REASON_SIPI_SIGNAL, 0,
                                                apic->sipi_vector & 0xFFUL);
-               return 0;
+                       return 0;
+               }
+               /* Fallthrough, the SIPI is completely ignored. */
        }
 
        /*