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

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On 08/25/2011 04:21 PM, Marcelo Tosatti wrote:
On Thu, Aug 25, 2011 at 07:42:10AM +0300, Avi Kivity wrote:
>  On 08/25/2011 05:04 AM, Marcelo Tosatti wrote:
>  >>
>  >>   It could increase the flood count independently of the accessed bit of
>  >>   the spte being updated, zapping after 3 attempts as it is now.
>  >>
>  >>   But additionally reset the flood count if the gpte appears to be valid
>  >>   (points to an existant gfn if the present bit is set, or if its zeroed).
>  >
>  >Well not zero, as thats a common pattern for non ptes.
>  >
>
>  On 32-bit with 4GB RAM, practically anything is a valid gpte.

The following could be required to consider a valid gpte, for write
flood detection purposes:

- Must be present.
- PageCacheDisable must be unset.
- PageWriteThrough must be unset.


Unless the guest is using PAT.

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

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