RE: [Xen-devel] scrubbing free'd pages

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-devel-
> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Keir Fraser
> Sent: 25 May 2010 14:40
> To: James Harper; Rafal Wojtczuk
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-devel] scrubbing free'd pages
> 
> On 25/05/2010 14:33, "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
> wrote:
> 
> >> Other memory pages the domain freeing the
> >> pages must scrub them itself before freeing them back to Xen.
> >
> > Is that true for a HVM domain making a decrease_reservation
> hypercall?
> > If so I should modify my code accordingly...
> 
> Yes you should.
> 
> > it also means I need to
> > know if the page I'm decreasing is an unpopulated PoD page or not
> too.
> 
> Certainly you could avoid it in that case. Actually I think the PoD
> code can
> detect and reclaim allocated-but-zeroed pages however. But not sure
> if you
> really have to rely on that or not.
> 

Yes, that's true, but it would be better if we didn't have to scrub pages and 
cause a populate immediately before an invalidate.

  Paul

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