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

[Xiao Guangrong]

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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