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SubjectRe: [PATCH v2 6/10] KVM MMU: don't write-protect if have new mapping to unsync page
On 04/25/2010 10:00 AM, Xiao Guangrong wrote:
> Two cases maybe happen in kvm_mmu_get_page() function:
>
> - one case is, the goal sp is already in cache, if the sp is unsync,
> we only need update it to assure this mapping is valid, but not
> mark it sync and not write-protect sp->gfn since it not broke unsync
> rule(one shadow page for a gfn)
>
> - another case is, the goal sp not existed, we need create a new sp
> for gfn, i.e, gfn (may)has another shadow page, to keep unsync rule,
> we should sync(mark sync and write-protect) gfn's unsync shadow page.
> After enabling multiple unsync shadows, we sync those shadow pages
> only when the new sp not allow to become unsync(also for the unsyc
> rule, the new rule is: allow all pte page become unsync)
>

Another interesting case is to create new shadow pages in the unsync
state. That can help when the guest starts a short lived process: we
can avoid write protecting its pagetables completely. Even if we do
sync them, we can sync them in a batch instead of one by one, saving IPIs.

--
error compiling committee.c: too many arguments to function



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