Re: [PATCH v3 9/11] KVM: MMU: prefetch ptes when intercepted guest #PF

Avi Kivity
2010-07-01T12:11:22Z

On 07/01/2010 04:11 AM, Xiao Guangrong wrote:
>
> Marcelo Tosatti wrote:
>
>
>>> +
>>> + addr = gfn_to_hva_many(vcpu->kvm, gfn,&entry);
>>> + if (kvm_is_error_hva(addr))
>>> + return -1;
>>> +
>>> + entry = min(entry, (int)(end - start));
>>> + ret = __get_user_pages_fast(addr, entry, 1, pages);
>>> + if (ret<= 0)
>>> + return -1;
>>>
>> Why can't you use gfn_to_pfn_atomic() here, one page at a time? Is
>> the overhead significant that this is worthwhile?
>>
>> You're bypassing the centralized interface.
>>
> I think it's worthwhile to do since we can reduce gup overhead, no reason
> to traverse process's page table again and again for the consecutive pages.
>

Then we should make the centralized interface work in terms of multiple
pages, and write the single-page interfaces in terms of the multipage
interfaces.

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