Set "blocked by NMI" flag if EPT violation happens during IRET from NMI
otherwise NMI can be called recursively causing stack corruption.

Signed-off-by: Gleb Natapov <g...@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 1f1da43..fa1984c 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5339,6 +5339,15 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
                return 0;
        }
 
+       /*
+        * EPT violation happened while executing iret from NMI,
+        * "blocked by NMI" bit has to be set before next VM entry.
+        * There are errata that may cause this bit to not be set:
+        * AAK134, BY25. 
+        */
+       if (exit_qualification & INTR_INFO_UNBLOCK_NMI)
+               vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO, 
GUEST_INTR_STATE_NMI);
+
        gpa = vmcs_read64(GUEST_PHYSICAL_ADDRESS);
        trace_kvm_page_fault(gpa, exit_qualification);
 
--
                        Gleb.
--
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