Re: [Xen-devel] map memory holes with same page

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 11:29 +0100 on 23 May (1306150145), James Harper wrote:
> I guess the only way to solve this is to stop every access hitting an
> emulation. Either I can map a common read-only page into every hole
> (which doesn't sound like a workable solution based on feedback so far),
> or Xen could keep a common read-only page and map it into a hole every
> time it is accessed (and then move the page when another hole is
> accessed), which would reduce the problem to emulation on the first time
> a different hole is accessed...

That's pretty ugly, though.  Is there really no way to tell Windows not
to bother hibernating your ballooned-out memory?  Surely there must be
equivalent cases in real hardware: GART framebuffers and so on?

What happens when Windows tries to load all your ballooned memory back
in on resume, btw?  Will it uncompress all those frames back onto
non-existent RAM?  (i.e. would we have to have this scratch frame be
writable - and if so would we need to properly discard writes to
correctly emulate missing RAM?)

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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