Patch "kvm: x86: Guest BNDCFGS requires guest MPX support" has been added to the 4.4-stable tree

Patch "kvm: x86: Guest BNDCFGS requires guest MPX support" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    kvm: x86: Guest BNDCFGS requires guest MPX support

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kvm-x86-guest-bndcfgs-requires-guest-mpx-support.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 4439af9f911ae0243ffe4e2dfc12bace49605d8b Mon Sep 17 00:00:00 2001
From: Jim Mattson <jmattson@google.com>
Date: Wed, 24 May 2017 10:49:25 -0700
Subject: kvm: x86: Guest BNDCFGS requires guest MPX support
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Jim Mattson <jmattson@google.com>

commit 4439af9f911ae0243ffe4e2dfc12bace49605d8b upstream.

The BNDCFGS MSR should only be exposed to the guest if the guest
supports MPX. (cf. the TSC_AUX MSR and RDTSCP.)

Fixes: 0dd376e709975779 ("KVM: x86: add MSR_IA32_BNDCFGS to msrs_to_save")
Change-Id: I3ad7c01bda616715137ceac878f3fa7e66b6b387
Signed-off-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kvm/cpuid.h |    8 ++++++++
 arch/x86/kvm/vmx.c   |    4 ++--
 2 files changed, 10 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -150,6 +150,14 @@ static inline bool guest_cpuid_has_pcomm
 	return best && (best->ebx & bit(X86_FEATURE_PCOMMIT));
 }
 
+static inline bool guest_cpuid_has_mpx(struct kvm_vcpu *vcpu)
+{
+	struct kvm_cpuid_entry2 *best;
+
+	best = kvm_find_cpuid_entry(vcpu, 7, 0);
+	return best && (best->ebx & bit(X86_FEATURE_MPX));
+}
+
 static inline bool guest_cpuid_has_rdtscp(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpuid_entry2 *best;
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2813,7 +2813,7 @@ static int vmx_get_msr(struct kvm_vcpu *
 		msr_info->data = vmcs_readl(GUEST_SYSENTER_ESP);
 		break;
 	case MSR_IA32_BNDCFGS:
-		if (!vmx_mpx_supported())
+		if (!vmx_mpx_supported() || !guest_cpuid_has_mpx(vcpu))
 			return 1;
 		msr_info->data = vmcs_read64(GUEST_BNDCFGS);
 		break;
@@ -2890,7 +2890,7 @@ static int vmx_set_msr(struct kvm_vcpu *
 		vmcs_writel(GUEST_SYSENTER_ESP, data);
 		break;
 	case MSR_IA32_BNDCFGS:
-		if (!vmx_mpx_supported())
+		if (!vmx_mpx_supported() || !guest_cpuid_has_mpx(vcpu))
 			return 1;
 		vmcs_write64(GUEST_BNDCFGS, data);
 		break;


Patches currently in stable-queue which might be from jmattson@google.com are

queue-4.4/kvm-x86-guest-bndcfgs-requires-guest-mpx-support.patch
queue-4.4/kvm-vmx-check-value-written-to-ia32_bndcfgs.patch
queue-4.4/kvm-vmx-do-not-disable-intercepts-for-bndcfgs.patch