FAILED: patch "[PATCH] kvm: vmx: allow host to access guest MSR_IA32_BNDCFGS" failed to apply to 4.12-stable tree

From 691bd4340bef49cf7e5855d06cf24444b5bf2d85 Mon Sep 17 00:00:00 2001

The patch below does not apply to the 4.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 691bd4340bef49cf7e5855d06cf24444b5bf2d85 Mon Sep 17 00:00:00 2001
From: Haozhong Zhang <[email protected]>
Date: Tue, 4 Jul 2017 10:27:41 +0800
Subject: [PATCH] kvm: vmx: allow host to access guest MSR_IA32_BNDCFGS

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.

Cc [email protected]

Signed-off-by Haozhong Zhang <[email protected]>

Signed-off-by Paolo Bonzini <[email protected]>

arch/x86/kvm/vmx.c +4 -2

index fb0471268a14..b4cfdcfdc1c1 100644
@@ -3196,7 +3196,8 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		msr_info->data = vmcs_readl(GUEST_SYSENTER_ESP);
 		break;
 	case MSR_IA32_BNDCFGS:
-		if (!kvm_mpx_supported() || !guest_cpuid_has_mpx(vcpu))
+		if (!kvm_mpx_supported() ||
+		    (!msr_info->host_initiated && !guest_cpuid_has_mpx(vcpu)))
 			return 1;
 		msr_info->data = vmcs_read64(GUEST_BNDCFGS);
 		break;

@@ -3278,7 +3279,8 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		vmcs_writel(GUEST_SYSENTER_ESP, data);
 		break;
 	case MSR_IA32_BNDCFGS:
-		if (!kvm_mpx_supported() || !guest_cpuid_has_mpx(vcpu))
+		if (!kvm_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))

Quoted 9 lines · On 07/18/17 17:06 +0200, [email protected] wrote:

The patch below does not apply to the 4.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

Hi Paolo and Greg,

I think the following patches should be backported as well before applying mine:

a8b6fda38f80 kvm: vmx: Do not disable intercepts for BNDCFGS 4439af9f911a kvm: x86: Guest BNDCFGS requires guest MPX support 4531662d1abf kvm: vmx: Check value written to IA32_BNDCFGS

I think the following patches should be backported as well before applying mine:

a8b6fda38f80 kvm: vmx: Do not disable intercepts for BNDCFGS 4439af9f911a kvm: x86: Guest BNDCFGS requires guest MPX support 4531662d1abf kvm: vmx: Check value written to IA32_BNDCFGS