Re: [patch 3/3] KVM: MMU: prepopulate the shadow on invlpg

[Avi Kivity <avi@redhat.com>]

Marcelo Tosatti wrote:
> Err, I'm on crack. The assumption is that the common case is pte
> invalidation + invlpg: kunmap_atomic, page aging clearing the 
> accessed bit, page reclaim.
>
> Linux COW will invalidate + invlpg (do_wp_page) first:
>
>                 entry = mk_pte(new_page, vma->vm_page_prot);
>                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
>                 /*
>                  * Clear the pte entry and flush it first, before
>                  * updating the
>                  * pte with the new entry. This will avoid a race
>                  * condition
>                  * seen in the presence of one thread doing SMC and
>                  * another
>                  * thread doing COW.
>                  */
>                 ptep_clear_flush_notify(vma, address, page_table);
>
> Not sure about Windows.
>
>   

Okay, so Linux won't win on this.  But is there any downside, apart from 
fetching the pte and reestablishing the spte?


-- 
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