Re: [RFC Patch 3/3] KVM/x86: Add tlb_remote_flush callback support for vmcs

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Tianyu Lan <Tianyu.Lan@microsoft.com> writes:

> On 6/12/2018 11:12 PM, Vitaly Kuznetsov wrote:
>> Tianyu Lan <Tianyu.Lan@microsoft.com> writes:
>> 
>>>
>>> +static int vmx_remote_flush_tlb(struct kvm *kvm)
>>> +{
>>> +	struct kvm_vcpu *vcpu = kvm_get_vcpu(kvm, 0);
>>> +
>>> +	if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
>>> +		return -1;
>> 
>> Why vcpu0? Can arch.mmu.root_hpa-s differ across vCPUs? What happens if
>> they do?
>
> Yes, it may take place that arch.mmu.root_hpa is differ across vCPUs.
> We may check all vcpu root_hpa and use the hypercall when there is only 
> one validated ept table. If not, go back to current way.
>

I'd suggest an optimization: keep track of wether root_hpas are equal
across all vcpus (check this on change).

-- 
  Vitaly