From: dv <dv@openbsd.org>
Date: Sun, 10 Dec 2023 21:25:14 +0000 (+0000)
Subject: vmm(4): flush EPTs after enabling VMX mode.
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=0a6d19ec1e7074703dcb7d5a3c1613d45bea1cd9;p=openbsd

vmm(4): flush EPTs after enabling VMX mode.

The Intel SDM states the vmxon/vmxoff instructions don't invalidate
any EPT states on the cpu and recommend invalidating the global
context. vmm(4) opportunistically disables and enables VMX mode as
vms are created or terminated, so this adds a recommended
housekeeping step per the SDM.

While here, tidy up the CR4 toggling by moving it to after the MSR
feature check.

ok mlarkin@
---

diff --git a/sys/arch/amd64/amd64/vmm_machdep.c b/sys/arch/amd64/amd64/vmm_machdep.c
index 82decbd3fed..8d8557471e0 100644
--- a/sys/arch/amd64/amd64/vmm_machdep.c
+++ b/sys/arch/amd64/amd64/vmm_machdep.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: vmm_machdep.c,v 1.11 2023/11/26 13:02:44 dv Exp $ */
+/* $OpenBSD: vmm_machdep.c,v 1.12 2023/12/10 21:25:14 dv Exp $ */
 /*
  * Copyright (c) 2014 Mike Larkin <mlarkin@openbsd.org>
  *
@@ -1055,6 +1055,7 @@ start_vmm_on_cpu(struct cpu_info *ci)
 {
 	uint64_t msr;
 	uint32_t cr4;
+	struct vmx_invept_descriptor vid;
 
 	/* No VMM mode? exit. */
 	if ((ci->ci_vmm_flags & CI_VMM_VMX) == 0 &&
@@ -1081,11 +1082,6 @@ start_vmm_on_cpu(struct cpu_info *ci)
 			ci->ci_vmxon_region->vr_revision =
 			    ci->ci_vmm_cap.vcc_vmx.vmx_vmxon_revision;
 
-			/* Set CR4.VMXE */
-			cr4 = rcr4();
-			cr4 |= CR4_VMXE;
-			lcr4(cr4);
-
 			/* Enable VMX */
 			msr = rdmsr(MSR_IA32_FEATURE_CONTROL);
 			if (msr & IA32_FEATURE_CONTROL_LOCK) {
@@ -1097,9 +1093,18 @@ start_vmm_on_cpu(struct cpu_info *ci)
 				wrmsr(MSR_IA32_FEATURE_CONTROL, msr);
 			}
 
-			/* Enter VMX mode */
+			/* Set CR4.VMXE */
+			cr4 = rcr4();
+			cr4 |= CR4_VMXE;
+			lcr4(cr4);
+
+			/* Enter VMX mode and clear EPTs on this cpu */
 			if (vmxon((uint64_t *)&ci->ci_vmxon_region_pa))
-				return;
+				panic("vmxon failed");
+
+			memset(&vid, 0, sizeof(vid));
+			if (invept(IA32_VMX_INVEPT_GLOBAL_CTX, &vid))
+				panic("invept failed");
 		}
 	}