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Re: [PATCH v2 6/9] x86/p2m: avoid unnecessary calls of write_p2m_entry_pre() hook
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Date: Fri, 8 Jan 2021 16:38:27 +0100
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On Fri, Nov 06, 2020 at 10:37:35AM +0100, Jan Beulich wrote:
> When shattering a large page, we first construct the new page table page
> and only then hook it up. The "pre" hook in this case does nothing, for
> the page starting out all blank. Avoid 512 calls into shadow code in
> this case by passing in INVALID_GFN, indicating the page being updated
> is (not yet) associated with any GFN. (The alternative to this change
> would be to actually pass in a correct GFN, which can't be all the same
> on every loop iteration.)
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
I agree it's silly to pass the gfn when populating the page table
page, as there's no gfn being updated (yet).
Thanks, Roger.
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