kvm: nVMX: Relax guest IA32_FEATURE_CONTROL constraints

Commit 37e4c997dadf ("KVM: VMX: validate individual bits of guest
MSR_IA32_FEATURE_CONTROL") broke the KVM_SET_MSRS ABI by instituting
new constraints on the data values that kvm would accept for the guest
MSR, IA32_FEATURE_CONTROL. Perhaps these constraints should have been
opt-in via a new KVM capability, but they were applied
indiscriminately, breaking at least one existing hypervisor.

Relax the constraints to allow either or both of
FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX and
FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX to be set when nVMX is
enabled. This change is sufficient to fix the aforementioned breakage.

Fixes: 37e4c997dadf ("KVM: VMX: validate individual bits of guest MSR_IA32_FEATURE_CONTROL")
Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d39475e..d175429 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7115,10 +7115,12 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
 
        if (nested_vmx_allowed(vcpu))
                to_vmx(vcpu)->msr_ia32_feature_control_valid_bits |=
+                       FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX |
                        FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX;
        else
                to_vmx(vcpu)->msr_ia32_feature_control_valid_bits &=
-                       ~FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX;
+                       ~(FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX |
+                         FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX);
 
        if (nested_vmx_allowed(vcpu)) {
                nested_vmx_cr_fixed1_bits_update(vcpu);