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SubjectRe: [PATCH v5 6/9] KVM: MMU: introduce pte_prefetch_topup_memory_cache()
On 07/13/2010 07:25 AM, Xiao Guangrong wrote:
>
>> Regressions? no. Or do you mean the problem already exists? Where?
>>
> I mean this is a exist problem, likes invlpg, pte-write and sync-page, there are
> speculative path that it's not real access, but marked dirty if pte is writable.
>

Right. We should fix those too.

Prefetch is much more worrying though, especially with ept. If a guest
is using just 1/8 of the pages, it can look to migration as if it's
using 100% of the pages. The impact can be pretty large.

In contrast, I'm not too worried about invlpg, as most times an access
will follow a miss, and usually a write access if we set a writeable
pte. Not sure about sync-page.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.



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