Patch "kvm: x86: Guest BNDCFGS requires guest MPX support" has been added to the 4.12-stable tree

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 4.12-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-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jim Mattson <[email protected]>
Date: Wed, 24 May 2017 10:49:25 -0700
Subject: kvm: x86: Guest BNDCFGS requires guest MPX support
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From: Jim Mattson <[email protected]>

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.)

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

@@ -144,6 +144,14 @@ static inline bool guest_cpuid_has_rtm(s
 	return best && (best->ebx & bit(X86_FEATURE_RTM));
 }
 
+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;

@@ -3195,7 +3195,7 @@ static int vmx_get_msr(struct kvm_vcpu *
 		msr_info->data = vmcs_readl(GUEST_SYSENTER_ESP);
 		break;
 	case MSR_IA32_BNDCFGS:
-		if (!kvm_mpx_supported())
+		if (!kvm_mpx_supported() || !guest_cpuid_has_mpx(vcpu))
 			return 1;
 		msr_info->data = vmcs_read64(GUEST_BNDCFGS);
 		break;

@@ -3277,7 +3277,7 @@ static int vmx_set_msr(struct kvm_vcpu *
 		vmcs_writel(GUEST_SYSENTER_ESP, data);
 		break;
 	case MSR_IA32_BNDCFGS:
-		if (!kvm_mpx_supported())
+		if (!kvm_mpx_supported() || !guest_cpuid_has_mpx(vcpu))
 			return 1;
 		vmcs_write64(GUEST_BNDCFGS, data);
 		break;

Patches currently in stable-queue which might be from [email protected] are

queue-4.12/kvm-x86-guest-bndcfgs-requires-guest-mpx-support.patch queue-4.12/kvm-vmx-check-value-written-to-ia32_bndcfgs.patch queue-4.12/kvm-vmx-do-not-disable-intercepts-for-bndcfgs.patch