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: stable@vger.kernel.org
Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index fb04712..b4cfdcf 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -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))