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

Maxim Levitsky
2022-11-17T14:35:10Z

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@redhat.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