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SubjectRe: [PATCH v5 8/9] KVM: MMU: combine guest pte read between fetch and pte prefetch


Marcelo Tosatti wrote:

>> -
>> - first_pte_gpa = gfn_to_gpa(sp->gfn) +
>> - (offset + i) * sizeof(pt_element_t);
>> -
>> - if (kvm_read_guest_atomic(vcpu->kvm, first_pte_gpa, gptep,
>> - sizeof(gptep)) < 0)
>> - return;
>> + gptep = gw->prefetch_ptes;
>
> Where do you reread the gpte in the prefetch path?
>

Marcelo,

Thanks for your review.

Below codes read gptes in the prefetch path:

index = sptep - sp->spt;
i = index & ~(PTE_PREFETCH_NUM - 1);
max = index | (PTE_PREFETCH_NUM - 1);

if (PTTYPE == 32)
offset = sp->role.quadrant << PT64_LEVEL_BITS;

first_pte_gpa = gfn_to_gpa(sp->gfn) +
(offset + i) * sizeof(pt_element_t);

if (kvm_read_guest_atomic(vcpu->kvm, first_pte_gpa, gptep,
sizeof(gptep)) < 0)
return;

It reads the 16 aligned items around sptep's corresponding gpte and this gpte
is also in this area. :-)


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