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Subject[PATCH 4/4] KVM: nSVM: avoid loss of pending IRQ/NMI before entering L2
Date
This patch reproduces for nSVM the change that was made for nVMX in
commit b5861e5cf2fc ("KVM: nVMX: Fix loss of pending IRQ/NMI before
entering L2"). While I do not have a test that breaks without it, I
cannot see why it would not be necessary since all events are unblocked
by VMRUN's setting of GIF back to 1.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/svm.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 0d773406f7ac..3df62257889a 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3574,6 +3574,10 @@ static bool nested_vmcb_checks(struct vmcb *vmcb)
static void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
struct vmcb *nested_vmcb, struct kvm_host_map *map)
{
+ bool evaluate_pending_interrupts =
+ is_intercept(svm, INTERCEPT_VINTR) ||
+ is_intercept(svm, INTERCEPT_IRET);
+
if (kvm_get_rflags(&svm->vcpu) & X86_EFLAGS_IF)
svm->vcpu.arch.hflags |= HF_HIF_MASK;
else
@@ -3660,7 +3664,21 @@ static void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,

svm->nested.vmcb = vmcb_gpa;

+ /*
+ * If L1 had a pending IRQ/NMI before executing VMRUN,
+ * which wasn't delivered because it was disallowed (e.g.
+ * interrupts disabled), L0 needs to evaluate if this pending
+ * event should cause an exit from L2 to L1 or be delivered
+ * directly to L2.
+ *
+ * Usually this would be handled by the processor noticing an
+ * IRQ/NMI window request. However, VMRUN can unblock interrupts
+ * by implicitly setting GIF, so force L0 to perform pending event
+ * evaluation by requesting a KVM_REQ_EVENT.
+ */
enable_gif(svm);
+ if (unlikely(evaluate_pending_interrupts))
+ kvm_make_request(KVM_REQ_EVENT, &svm->vcpu);

mark_all_dirty(svm->vmcb);
}
--
1.8.3.1
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