Patch "kvm: vmx: allow host to access guest MSR_IA32_BNDCFGS" has been added to the 4.4-stable tree

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

kvm: vmx: allow host to access guest MSR_IA32_BNDCFGS

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-vmx-allow-host-to-access-guest-msr_ia32_bndcfgs.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 <[email protected]> know about it.

From: Haozhong Zhang <[email protected]>
Date: Tue, 4 Jul 2017 10:27:41 +0800
Subject: kvm: vmx: allow host to access guest MSR_IA32_BNDCFGS

From: Haozhong Zhang <[email protected]>

commit 691bd4340bef49cf7e5855d06cf24444b5bf2d85 upstream.

It's easier for host applications, such as QEMU, if they can always access guest MSR_IA32_BNDCFGS in VMCS, even though MPX is disabled in guest cpuid.

---
 arch/x86/kvm/vmx.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

@@ -2813,7 +2813,8 @@ 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() || !guest_cpuid_has_mpx(vcpu))
+		if (!vmx_mpx_supported() ||
+		    (!msr_info->host_initiated && !guest_cpuid_has_mpx(vcpu)))
 			return 1;
 		msr_info->data = vmcs_read64(GUEST_BNDCFGS);
 		break;

@@ -2890,7 +2891,8 @@ static int vmx_set_msr(struct kvm_vcpu *
 		vmcs_writel(GUEST_SYSENTER_ESP, data);
 		break;
 	case MSR_IA32_BNDCFGS:
-		if (!vmx_mpx_supported() || !guest_cpuid_has_mpx(vcpu))
+		if (!vmx_mpx_supported() ||
+		    (!msr_info->host_initiated && !guest_cpuid_has_mpx(vcpu)))
 			return 1;
 		if (is_noncanonical_address(data & PAGE_MASK) ||
 		    (data & MSR_IA32_BNDCFGS_RSVD))

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

queue-4.4/kvm-vmx-allow-host-to-access-guest-msr_ia32_bndcfgs.patch