KVM: x86: don't expose MSR_IA32_UMWAIT_CONTROL unconditionally

This msr is only available when the host supports WAITPKG feature.

This breaks a nested guest, if the L1 hypervisor is set to ignore
unknown msrs, because the only other safety check that the
kernel does is that it attempts to read the msr and
rejects it if it gets an exception.

Cc: stable@vger.kernel.org
Fixes: 6e3ba4abce ("KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL")
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20200523161455.3940-3-mlevitsk@redhat.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c17e6eb9ad43d84fece0aeb875bfd903e69a252c..e0083a08da9e7731d7224256553f8f0795407cc4 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5242,6 +5242,10 @@ static void kvm_init_msr_list(void)
                        if (!kvm_cpu_cap_has(X86_FEATURE_RDTSCP))
                                continue;
                        break;
+               case MSR_IA32_UMWAIT_CONTROL:
+                       if (!kvm_cpu_cap_has(X86_FEATURE_WAITPKG))
+                               continue;
+                       break;
                case MSR_IA32_RTIT_CTL:
                case MSR_IA32_RTIT_STATUS:
                        if (!kvm_cpu_cap_has(X86_FEATURE_INTEL_PT))