linux-kernel - [PATCH] KVM: x86: Work around buggy MPX platform

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Message-ID: <DE8DF0795D48FD4CA783C40EC82923350155757D@SHSMSX152.ccr.corp.intel.com>
Date:	Mon, 10 Mar 2014 08:48:15 +0000
From:	"Liu, Jinsong" <jinsong.liu@...el.com>
To:	Paolo Bonzini <pbonzini@...hat.com>,
	"'kvm@...r.kernel.org'" <kvm@...r.kernel.org>,
	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
	"'qemu-devel@...gnu.org'" <qemu-devel@...gnu.org>
Subject: [PATCH] KVM: x86: Work around buggy MPX platform

>From 5854070994c5002b3a37577165ed3e82f36f712d Mon Sep 17 00:00:00 2001
From: Liu Jinsong <jinsong.liu@...el.com>
Date: Sat, 8 Mar 2014 04:40:02 +0800
Subject: [PATCH] KVM: x86: Work around buggy MPX platform

Work around buggy MPX platform which support MSR_IA32_BNDCFGS
but has issue at, say, VMX ucode.

Signed-off-by: Liu Jinsong <jinsong.liu@...el.com>
---
 arch/x86/kvm/x86.c |   14 +++++++++++++-
 1 files changed, 13 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1e91a24..1fc184d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3936,6 +3936,16 @@ static void kvm_init_msr_list(void)
 	for (i = j = KVM_SAVE_MSRS_BEGIN; i < ARRAY_SIZE(msrs_to_save); i++) {
 		if (rdmsr_safe(msrs_to_save[i], &dummy[0], &dummy[1]) < 0)
 			continue;
+
+		/*
+		 * Work around some buggy MPX platform which support
+		 * MSR_IA32_BNDCFGS but has issue at, say, VMX ucode.
+		 */
+		if ((msrs_to_save[i] == MSR_IA32_BNDCFGS) &&
+			(kvm_x86_ops->mpx_supported   ?
+			!kvm_x86_ops->mpx_supported() : 1))
+				continue;
+
 		if (j < i)
 			msrs_to_save[j] = msrs_to_save[i];
 		j++;
@@ -5576,9 +5586,11 @@ int kvm_arch_init(void *opaque)
 		goto out_free_percpu;
 
 	kvm_set_mmio_spte_mask();
-	kvm_init_msr_list();
 
 	kvm_x86_ops = ops;
+
+	kvm_init_msr_list();
+
 	kvm_mmu_set_mask_ptes(PT_USER_MASK, PT_ACCESSED_MASK,
 			PT_DIRTY_MASK, PT64_NX_MASK, 0);
 
-- 
1.7.1
--
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