Use the new MSR feature framework to expose the ARCH_CAPABILITIES MSR to
userspace.  This way, userspace can access the capabilities even if it
does not have the permissions to read MSRs.

Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
 arch/x86/kvm/vmx.c | 12 +++++++++++-
 arch/x86/kvm/x86.c |  1 +
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 130fca0ea1bf..99689061e11e 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3228,7 +3228,17 @@ static inline bool vmx_feature_control_msr_valid(struct 
kvm_vcpu *vcpu,
 
 static int vmx_get_msr_feature(struct kvm_msr_entry *msr)
 {
-       return 1;
+       switch (msr->index) {
+       case MSR_IA32_ARCH_CAPABILITIES:
+               if (!boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES))
+                       return 1;
+               rdmsrl(msr->index, msr->data);
+               break;
+       default:
+               return 1;
+       }
+
+       return 0;
 }
 
 /*
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 54b4ed55945b..e9a8cc9e3b2b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1054,6 +1054,7 @@ bool kvm_rdpmc(struct kvm_vcpu *vcpu)
  * can be used by a hypervisor to validate requested CPU features.
  */
 static u32 msr_based_features[] = {
+       MSR_IA32_ARCH_CAPABILITIES,
        MSR_F10H_DECFG,
 };
 
-- 
1.8.3.1

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