Re: [PATCH 11/11] KVM: MMU: improve write flooding detected

Avi Kivity
2011-07-27T11:08:35Z

On 07/27/2011 01:20 PM, Xiao Guangrong wrote:
> >> }
> >
> > I think this is a little dangerous. A guest kernel may be instantiating multiple gptes on a page fault, but guest userspace hits only one of them (the one which caused the page fault) - I think Windows does this, but I'm not sure.
> >
>
> I think this case is not bad: if the guest kernel need to write multiple gptes (>=3),
> it will cause many page fault, we do better zap the shadow page and let it become writable as
> soon as possible.
> (And, we have pte-fetch, it can quickly establish the mapping for a new shadow page)

Actually, what should save us is unsync pages. Why are we hitting this
path at all?

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