linux-kernel - [PATCH v2 08/24] KVM: nVMX: Ignore SIPI that arrives in L2 when vCPU is not in WFS

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Date:   Fri, 15 Jul 2022 20:42:10 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Oliver Upton <oupton@...gle.com>,
        Peter Shier <pshier@...gle.com>
Subject: [PATCH v2 08/24] 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@...gle.com>
Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/kvm/vmx/nested.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index bc5759f82a3f..104f233ddd5d 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3925,10 +3925,12 @@ 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. */
 	}
 
 	/*
-- 
2.37.0.170.g444d1eabd0-goog