linux-kernel - [PATCH v3 4/7] KVM: SVM: Inject NMIs when restricted injection is active

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Message-ID: <20241127225539.5567-5-huibo.wang@amd.com>
Date: Wed, 27 Nov 2024 22:55:36 +0000
From: Melody Wang <huibo.wang@....com>
To: <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <x86@...nel.org>
CC: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
	<pbonzini@...hat.com>, Tom Lendacky <thomas.lendacky@....com>, "Neeraj
 Upadhyay" <neeraj.upadhyay@....com>, Ashish Kalra <ashish.kalra@....com>,
	Michael Roth <michael.roth@....com>, Pankaj Gupta <pankaj.gupta@....com>,
	Melody Wang <huibo.wang@....com>
Subject: [PATCH v3 4/7] KVM: SVM: Inject NMIs when restricted injection is active

When restricted injection is active, only #HV exceptions can be injected into
the SEV-SNP guest.

Detect that restricted injection feature is active for the guest, and then
follow the #HV doorbell communication from the GHCB specification to inject
NMIs.

Co-developed-by: Thomas Lendacky <thomas.lendacky@....com>
Signed-off-by: Thomas Lendacky <thomas.lendacky@....com>
Signed-off-by: Melody Wang <huibo.wang@....com>
---
 arch/x86/kvm/svm/sev.c | 19 ++++++++++++++++---
 arch/x86/kvm/svm/svm.c |  8 ++++++++
 arch/x86/kvm/svm/svm.h |  1 +
 3 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 77dbc7dea974..00d1f620d14a 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -5077,7 +5077,10 @@ static void __sev_snp_inject(enum inject_type type, struct kvm_vcpu *vcpu)
 		return;
 	}
 
-	hvdb->events.vector = vcpu->arch.interrupt.nr;
+	if (type == INJECT_NMI)
+		hvdb->events.nmi = 1;
+	else
+		hvdb->events.vector = vcpu->arch.interrupt.nr;
 
 	prepare_hv_injection(svm, hvdb);
 
@@ -5157,10 +5160,17 @@ void sev_snp_cancel_injection(struct kvm_vcpu *vcpu)
 	/* Copy info back into event_inj field (replaces #HV) */
 	svm->vmcb->control.event_inj = SVM_EVTINJ_VALID;
 
+	/*
+	 * KVM only injects a single event each time (prepare_hv_injection),
+	 * so when events.nmi is true, the vector will be zero
+	 */
 	if (hvdb->events.vector)
 		svm->vmcb->control.event_inj |= hvdb->events.vector |
 						SVM_EVTINJ_TYPE_INTR;
 
+	if (hvdb->events.nmi)
+		svm->vmcb->control.event_inj |= SVM_EVTINJ_TYPE_NMI;
+
 	hvdb->events.pending_events = 0;
 
 out:
@@ -5186,8 +5196,11 @@ bool sev_snp_blocked(enum inject_type type, struct kvm_vcpu *vcpu)
 	if (!hvdb)
 		return true;
 
-	/* Indicate interrupts blocked based on guest acknowledgment */
-	blocked = !!hvdb->events.vector;
+	/* Indicate NMIs and interrupts blocked based on guest acknowledgment */
+	if (type == INJECT_NMI)
+		blocked = hvdb->events.nmi;
+	else
+		blocked = !!hvdb->events.vector;
 
 	unmap_hvdb(vcpu, &hvdb_map);
 
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 99f35a54b6ad..91bf17684bc8 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3616,6 +3616,9 @@ static void svm_inject_nmi(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 
+	if (sev_snp_inject(INJECT_NMI, vcpu))
+		goto status;
+
 	svm->vmcb->control.event_inj = SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_NMI;
 
 	if (svm->nmi_l1_to_l2)
@@ -3630,6 +3633,8 @@ static void svm_inject_nmi(struct kvm_vcpu *vcpu)
 		svm->nmi_masked = true;
 		svm_set_iret_intercept(svm);
 	}
+
+status:
 	++vcpu->stat.nmi_injections;
 }
 
@@ -3800,6 +3805,9 @@ bool svm_nmi_blocked(struct kvm_vcpu *vcpu)
 	if (!gif_set(svm))
 		return true;
 
+	if (sev_snp_is_rinj_active(vcpu))
+		return sev_snp_blocked(INJECT_NMI, vcpu);
+
 	if (is_guest_mode(vcpu) && nested_exit_on_nmi(svm))
 		return false;
 
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 724e0b197b2c..b6e833f455ae 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -57,6 +57,7 @@ extern int lbrv;
 
 enum inject_type {
 	INJECT_IRQ,
+	INJECT_NMI,
 };
 
 /*
-- 
2.34.1