Re: [PATCH v3 02/17] KVM: x86/xen: fix Xen hypercall page msr handling

[Vitaly Kuznetsov <vkuznets@redhat.com>]

David Woodhouse <dwmw2@infradead.org> writes:

>>> @@ -3001,6 +3001,9 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu,
>>struct msr_data *msr_info)
>>>  	u32 msr = msr_info->index;
>>>  	u64 data = msr_info->data;
>>>  
>>> +	if (msr && (msr == vcpu->kvm->arch.xen_hvm_config.msr))
>>> +		return xen_hvm_config(vcpu, data);
>>> +
>>
>>Can we generalize this maybe? E.g. before handling KVM and
>>architectural
>>MSRs we check that the particular MSR is not overriden by an emulated
>>hypervisor, 
>>
>>e.g.
>>	if (kvm_emulating_hyperv(kvm) && kvm_hyperv_msr_overriden(kvm,msr)
>>		return kvm_hyperv_handle_msr(kvm, msr);
>>	if (kvm_emulating_xen(kvm) && kvm_xen_msr_overriden(kvm,msr)
>>		return kvm_xen_handle_msr(kvm, msr);
>
> That smells a bit like overengineering. As I said, I did have a play
> with "improving" Joao's original patch but nothing I tried actually
> made more sense to me than this once the details were ironed out.

This actually looks more or less like hypercall distinction from after PATCH3:

	if (kvm_xen_hypercall_enabled(vcpu->kvm))
		return kvm_xen_hypercall(vcpu);

        if (kvm_hv_hypercall_enabled(vcpu->kvm))
  	        return kvm_hv_hypercall(vcpu);

....

so my idea was why not do the same for MSRs?

-- 
Vitaly