If a VM-exit happens during an NMI injection then clear the "NMI Blocking" bit

in the Guest Interruptibility-state VMCS field.

If we fail to do this then a subsequent VM-entry will fail because it is an
error to inject an NMI into the guest while "NMI Blocking" is turned on. This
is described in "Checks on Guest Non-Register State" in the Intel SDM.

Submitted by:	David Reed (david.reed@tidalscale.com)

2 files changed, 26 insertions, 12 deletions

diff --git a/sys/amd64/vmm/intel/vmcs.h b/sys/amd64/vmm/intel/vmcs.h
index fde93e522674..cd2f84b8978b 100644
--- a/sys/amd64/vmm/intel/vmcs.h
+++ b/sys/amd64/vmm/intel/vmcs.h
@@ -333,10 +333,10 @@ vmcs_write(uint32_t encoding, uint64_t val)
 /*
  * VMCS interrupt information fields
  */
-#define	VMCS_INTR_INFO_VALID		(1U << 31)
-#define	VMCS_INTR_INFO_TYPE(info)	(((info) >> 8) & 0x7)
-#define	VMCS_INTR_INFO_HW_INTR		(0 << 8)
-#define	VMCS_INTR_INFO_NMI		(2 << 8)
+#define	VMCS_INTR_VALID		(1U << 31)
+#define	VMCS_INTR_T_MASK	0x700		/* Interruption-info type */
+#define	VMCS_INTR_T_HWINTR	(0 << 8)
+#define	VMCS_INTR_T_NMI		(2 << 8)
 
 /*
  * VMCS IDT-Vectoring information fields
diff --git a/sys/amd64/vmm/intel/vmx.c b/sys/amd64/vmm/intel/vmx.c
index a4e0a851e982..0c3717596489 100644
--- a/sys/amd64/vmm/intel/vmx.c
+++ b/sys/amd64/vmm/intel/vmx.c
@@ -1065,7 +1065,7 @@ vmx_inject_nmi(struct vmx *vmx, int vcpu)
 	 * Inject the virtual NMI. The vector must be the NMI IDT entry
 	 * or the VMCS entry check will fail.
 	 */
-	info = VMCS_INTR_INFO_NMI | VMCS_INTR_INFO_VALID;
+	info = VMCS_INTR_T_NMI | VMCS_INTR_VALID;
 	info |= IDT_NMI;
 	vmcs_write(VMCS_ENTRY_INTR_INFO, info);
 
@@ -1103,7 +1103,7 @@ vmx_inject_interrupts(struct vmx *vmx, int vcpu, struct vlapic *vlapic)
 	 * because of a pending AST.
 	 */
 	info = vmcs_read(VMCS_ENTRY_INTR_INFO);
-	if (info & VMCS_INTR_INFO_VALID)
+	if (info & VMCS_INTR_VALID)
 		return;
 
 	/*
@@ -1134,7 +1134,7 @@ vmx_inject_interrupts(struct vmx *vmx, int vcpu, struct vlapic *vlapic)
 		goto cantinject;
 
 	/* Inject the interrupt */
-	info = VMCS_INTR_INFO_HW_INTR | VMCS_INTR_INFO_VALID;
+	info = VMCS_INTR_T_HWINTR | VMCS_INTR_VALID;
 	info |= vector;
 	vmcs_write(VMCS_ENTRY_INTR_INFO, info);
 
@@ -1444,10 +1444,12 @@ vmx_exit_process(struct vmx *vmx, int vcpu, struct vm_exit *vmexit)
 	int error, handled;
 	struct vmxctx *vmxctx;
 	struct vlapic *vlapic;
-	uint32_t eax, ecx, edx, idtvec_info, idtvec_err, intr_info, reason;
+	uint32_t eax, ecx, edx, gi, idtvec_info, idtvec_err, intr_info, reason;
 	uint64_t qual, gpa;
 	bool retu;
 
+	CTASSERT((PINBASED_CTLS_ONE_SETTING & PINBASED_VIRTUAL_NMI) != 0);
+
 	handled = 0;
 	vmxctx = &vmx->ctx[vcpu];
 
@@ -1480,6 +1482,18 @@ vmx_exit_process(struct vmx *vmx, int vcpu, struct vm_exit *vmexit)
 				vmcs_write(VMCS_ENTRY_EXCEPTION_ERROR,
 				    idtvec_err);
 			}
+			/*
+			 * If 'virtual NMIs' are being used and the VM-exit
+			 * happened while injecting an NMI during the previous
+			 * VM-entry, then clear "blocking by NMI" in the Guest
+			 * Interruptibility-state.
+			 */
+			if ((idtvec_info & VMCS_INTR_T_MASK) ==
+			    VMCS_INTR_T_NMI) {
+				 gi = vmcs_read(VMCS_GUEST_INTERRUPTIBILITY);
+				 gi &= ~VMCS_INTERRUPTIBILITY_NMI_BLOCKING;
+				 vmcs_write(VMCS_GUEST_INTERRUPTIBILITY, gi);
+			}
 			vmcs_write(VMCS_ENTRY_INST_LENGTH, vmexit->inst_length);
 		}
 	default:
@@ -1556,8 +1570,8 @@ vmx_exit_process(struct vmx *vmx, int vcpu, struct vm_exit *vmexit)
 		 * this virtual interrupt during the subsequent VM enter.
 		 */
 		intr_info = vmcs_read(VMCS_EXIT_INTR_INFO);
-		KASSERT((intr_info & VMCS_INTR_INFO_VALID) != 0 &&
-		    VMCS_INTR_INFO_TYPE(intr_info) == 0,
+		KASSERT((intr_info & VMCS_INTR_VALID) != 0 &&
+		    (intr_info & VMCS_INTR_T_MASK) == VMCS_INTR_T_HWINTR,
 		    ("VM exit interruption info invalid: %#x", intr_info));
 		vmx_trigger_hostintr(intr_info & 0xff);
 
@@ -2039,11 +2053,11 @@ vmx_inject(void *arg, int vcpu, int type, int vector, uint32_t code,
 	if (error)
 		return (error);
 
-	if (info & VMCS_INTR_INFO_VALID)
+	if (info & VMCS_INTR_VALID)
 		return (EAGAIN);
 
 	info = vector | (type_map[type] << 8) | (code_valid ? 1 << 11 : 0);
-	info |= VMCS_INTR_INFO_VALID;
+	info |= VMCS_INTR_VALID;
 	error = vmcs_setreg(vmcs, 0, VMCS_IDENT(VMCS_ENTRY_INTR_INFO), info);
 	if (error != 0)
 		return (error);