linux-kernel - [PATCH v2 16/24] KVM: x86: Evaluate ability to inject SMI/NMI/IRQ after potential VM-Exit

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Message-Id: <20220715204226.3655170-17-seanjc@google.com>
Date:   Fri, 15 Jul 2022 20:42:18 +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 16/24] KVM: x86: Evaluate ability to inject SMI/NMI/IRQ
 after potential VM-Exit

Determine whether or not new events can be injected after checking nested
events.  If a VM-Exit occurred during nested event handling, any previous
event that needed re-injection is gone from's KVM perspective; the event
is captured in the vmc*12 VM-Exit information, but doesn't exist in terms
of what needs to be done for entry to L1.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/kvm/x86.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9e20d34d856d..795c799fc767 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9657,7 +9657,7 @@ static void kvm_inject_exception(struct kvm_vcpu *vcpu)
 
 static int inject_pending_event(struct kvm_vcpu *vcpu, bool *req_immediate_exit)
 {
-	bool can_inject = !kvm_event_needs_reinjection(vcpu);
+	bool can_inject;
 	int r;
 
 	/*
@@ -9722,7 +9722,13 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool *req_immediate_exit)
 	if (r < 0)
 		goto out;
 
-	/* try to inject new event if pending */
+	/*
+	 * New events, other than exceptions, cannot be injected if KVM needs
+	 * to re-inject a previous event.  See above comments on re-injecting
+	 * for why pending exceptions get priority.
+	 */
+	can_inject = !kvm_event_needs_reinjection(vcpu);
+
 	if (vcpu->arch.exception.pending) {
 		/*
 		 * Fault-class exceptions, except #DBs, set RF=1 in the RFLAGS
-- 
2.37.0.170.g444d1eabd0-goog