From: dv <dv@openbsd.org>
Date: Mon, 30 Jan 2023 14:05:36 +0000 (+0000)
Subject: vmm(4): expose PKU cpuid bit if in use on host.
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=ef14a9e8cae106563ff9ce15d913365f9ad3fa0e;p=openbsd

vmm(4): expose PKU cpuid bit if in use on host.

We are using {rd,wr}pkru instructions for saving and restoring the
PKRU, so tie the exposure of PKU feature bit to vmm having the
ability to properly handle the guest state.
---

diff --git a/sys/arch/amd64/amd64/vmm.c b/sys/arch/amd64/amd64/vmm.c
index 55244baa3e5..d8c8abc96f3 100644
--- a/sys/arch/amd64/amd64/vmm.c
+++ b/sys/arch/amd64/amd64/vmm.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: vmm.c,v 1.336 2023/01/30 02:32:01 dv Exp $	*/
+/*	$OpenBSD: vmm.c,v 1.337 2023/01/30 14:05:36 dv Exp $	*/
 /*
  * Copyright (c) 2014 Mike Larkin <mlarkin@openbsd.org>
  *
@@ -7035,6 +7035,14 @@ vmm_handle_cpuid(struct vcpu *vcpu)
 			*rbx = curcpu()->ci_feature_sefflags_ebx & VMM_SEFF0EBX_MASK;
 			*rcx = curcpu()->ci_feature_sefflags_ecx & VMM_SEFF0ECX_MASK;
 			*rdx = curcpu()->ci_feature_sefflags_edx & VMM_SEFF0EDX_MASK;
+			/*
+			 * Only expose PKU support if we've detected it in use
+			 * on the host.
+			 */
+			if (vmm_softc->pkru_enabled)
+				*rcx |= SEFF0ECX_PKU;
+			else
+				*rcx &= ~SEFF0ECX_PKU;
 		} else {
 			/* Unsupported subleaf */
 			DPRINTF("%s: function 0x07 (SEFF) unsupported subleaf "