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

[Marcelo Tosatti <mtosatti@redhat.com>]

On Wed, Jul 07, 2010 at 09:23:15AM +0800, Xiao Guangrong wrote:
> 
> 
> 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. :-)

But you removed that in patch 8?