On 24/04/20 13:37, Jon Doron wrote:

+static int syndbg_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host)
+{
+	struct kvm_hv_syndbg *syndbg = vcpu_to_hv_syndbg(vcpu);
+
+	if (!syndbg->active && !host)
+		return 1;
+

One small thing: is the ENABLE_CAP and active field needed?  Can you
just check if the guest has the syndbg CPUID bits set?

Thanks,

Paolo