Re: [PATCH V4 4/7] KVM, pkeys: add pkeys support for permission_fault logic

[Xiao Guangrong <guangrong.xiao@linux.intel.com>]

On 03/07/2016 04:36 AM, Paolo Bonzini wrote:
>
>
> On 06/03/2016 09:00, Xiao Guangrong wrote:
>>>
>>>        if (vcpu_match_mmio_gva(vcpu, gva)
>>>            && !permission_fault(vcpu, vcpu->arch.walk_mmu,
>>> -                 vcpu->arch.access, access)) {
>>> +                 vcpu->arch.access, 0, access)) {
>>
>> No. The pkey is not always 0.
>>
>> We should cache PKEY for the mmio access and use it here to check if the
>> right is adequate.
>
> This is just an optimization I think, so it can have false negatives (it
> won't have many in practice because MMIO accesses are usually done in
> supervisor mode).  The actual check is done when
> vcpu->arch.walk_mmu->gva_to_gpa is called.

Okay, this patchset disabled PKEY for soft mmu (ept = 0) so it should be safe,
however some comments would be appreciated.