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RE: [Xen-devel] Re: xen crash in tmem: checking a xen pfn for domain own

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: RE: [Xen-devel] Re: xen crash in tmem: checking a xen pfn for domain ownership
From: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Date: Mon, 20 Sep 2010 07:12:57 -0700 (PDT)
Cc: Xen-devel <Xen-devel@xxxxxxxxxxxxxxxxxxx>
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> On 20/09/2010 08:16, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
> >>>> On 17.09.10 at 21:32, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
> wrote:
> >> Oh, depending on what you want to do with the page you may well want
> to
> >> get_page(current->domain, page). You don't hold a lock on the
> domain's p2m,
> >> so page ownerships can change under your feet, and hence getting a
> reference
> >> to the page, and checking the page's ownership at the same time,
> might be
> >> wise. And if you want to modify the page you should probably use
> >> get_page_and_type(..., PGT_writable_page).
> >
> > That's particularly important for the pv case, where gfn_to_mfn() is
> > a no-op.

Thanks, Jan and Keir, I'll take a look at it.
> Yes, I actually forgot about the PV case, and I think that's the only
> case
> that matters for tmem. :-)

Tmem works for HVM guests now too (on top of Stefano's PV-on-HVM
Linux kernel patches), though I haven't tested it in awhile.

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