[PATCH 2/3] KVM: x86: Reject enabling KVM_CAP_X86_BUS_LOCK_EXIT when !kvm_caps.has_bus_lock_exit

[Xiaoyao Li]

Return -EINVAL to reject the enabling of KVM_CAP_X86_BUS_LOCK_EXIT from
userspace when kvm_caps.has_bus_lock_exit is false.

For KVM_BUS_LOCK_DETECTION_EXIT, if KVM doesn't support BUS LOCK EXIT,
return error to userspace instead of success.

For KVM_BUS_LOCK_DETECTION_OFF, it seems OK to allow it when KVM doesn't
support bus_lock_exit. But from an API perspective, it implies
inconsistency that KVM_CAP_X86_BUS_LOCK_EXIT reports 0 but setting
KVM_BUS_LOCK_DETECTION_OFF is allowed. To keep it consistent, also
return error for KVM_BUS_LOCK_DETECTION_OFF when KVM doesn't support
BUS LOCK EXIT.

Fixes: fe6b6bc802b4 ("KVM: VMX: Enable bus lock VM exit")
Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
---
---
 arch/x86/kvm/x86.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d94b59140c45..3d8422d1cd04 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4058,8 +4058,10 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 		    (cap->args[0] & KVM_BUS_LOCK_DETECTION_EXIT))
 			break;
 
-		if (kvm_caps.has_bus_lock_exit &&
-		    cap->args[0] & KVM_BUS_LOCK_DETECTION_EXIT)
+		if (!kvm_caps.has_bus_lock_exit)
+			break;
+
+		if (cap->args[0] & KVM_BUS_LOCK_DETECTION_EXIT)
 			kvm->arch.bus_lock_detection_enabled = true;
 		r = 0;
 		break;
-- 
2.43.0