linux-kernel - [PATCH 09/13] KVM: SVM: allow NMI window with vNMI

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Date:   Thu, 17 Nov 2022 16:32:38 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sandipan Das <sandipan.das@....com>,
        Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
        Jing Liu <jing2.liu@...el.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Wyes Karny <wyes.karny@....com>,
        Borislav Petkov <bp@...en8.de>,
        Babu Moger <babu.moger@....com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Jim Mattson <jmattson@...gle.com>, x86@...nel.org,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 09/13] KVM: SVM: allow NMI window with vNMI

When the vNMI is enabled, the only case when the KVM will use an NMI
window is when the vNMI injection is pending.

In this case on next IRET/RSM/STGI, the injection has to be complete
and a new NMI can be injected.

Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/kvm/svm/svm.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index cfec4c98bb589b..eaa30f8ace518d 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2477,7 +2477,10 @@ static int iret_interception(struct kvm_vcpu *vcpu)
 	struct vcpu_svm *svm = to_svm(vcpu);
 
 	++vcpu->stat.nmi_window_exits;
-	vcpu->arch.hflags |= HF_IRET_MASK;
+
+	if (!is_vnmi_enabled(svm))
+		vcpu->arch.hflags |= HF_IRET_MASK;
+
 	if (!sev_es_guest(vcpu->kvm)) {
 		svm_clr_intercept(svm, INTERCEPT_IRET);
 		svm->nmi_iret_rip = kvm_rip_read(vcpu);
@@ -3735,9 +3738,6 @@ static void svm_enable_nmi_window(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 
-	if (is_vnmi_enabled(svm))
-		return;
-
 	if ((vcpu->arch.hflags & (HF_NMI_MASK | HF_IRET_MASK)) == HF_NMI_MASK)
 		return; /* IRET will cause a vm exit */
 
@@ -3751,9 +3751,14 @@ static void svm_enable_nmi_window(struct kvm_vcpu *vcpu)
 	 * Something prevents NMI from been injected. Single step over possible
 	 * problem (IRET or exception injection or interrupt shadow)
 	 */
-	svm->nmi_singlestep_guest_rflags = svm_get_rflags(vcpu);
-	svm->nmi_singlestep = true;
-	svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF);
+
+	if (is_vnmi_enabled(svm)) {
+		svm_set_intercept(svm, INTERCEPT_IRET);
+	} else {
+		svm->nmi_singlestep_guest_rflags = svm_get_rflags(vcpu);
+		svm->nmi_singlestep = true;
+		svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF);
+	}
 }
 
 static void svm_flush_tlb_current(struct kvm_vcpu *vcpu)
-- 
2.34.3