Re: [Xen-devel] Re: [PATCH]Add a flag for shadow pages

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 04/03/2009 09:56, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:

> Another would be to create a new function page_get_reference_and_owner()
> which obtains a reference on a guest page and *returns* the (now known
> valid) domain pointer. Probably this is nicer actually. Then all existing
> users of page_get_owner() need checking to ensure they don't need to use the
> new more expensive function -- I think some are probably actually unsafe now
> that shadow pages clobber the domain field.

I'm working on this by the way. I'll clean up everything except shadow uses
of page_get_owner(). The only two possibly suspect uses I can see (most are
just ASSERT/BUG_ON uses I think are okay):
 * sh_mfn_is_a_pagetable()
 * shadow_get_page_from_l1e()

It'd be good if Tim or Gianluca would check whether these need to be more
careful -- could page_get_owner() return a duff non-NULL value in either of
these functions? This could only happen if the pages they work on could
possibly actually be shadow pages with clobbered page owner field.

 -- Keir



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