Re: [Xen-devel] [PATCH 2 of 4 RFC] xen, pod: Check zero-check pages returned by the balloon driver

[Tim Deegan <tim@xxxxxxx>]

At 12:54 +0100 on 08 Jun (1339160092), George Dunlap wrote:
> +        else if( p2m_is_ram(t) )
> +        {
> +            if ( steal_for_cache )
> +            {
> +                struct page_info *page;
> +                
> +                ASSERT(mfn_valid(mfn));

I think this assertion is broken by the paging code, which adds
paged-out pages to the RAM types.  One fix is to undo that change and
have p2m_is_ram() only be true for present pages, but I think for 4.2 it
would be less disruptive to test here for the paged-out and paging
types.

Cc'ing Andres on the larger question -- do you think we can have
p2m_is_ram() imply mfn_valid() again?  I'm not sure whether it will make
things cleaner (or at least move the burden of handling paged-out memory
into the paging code) or add more boilerplate to paths where the paging
will be handled after a check for p2m_os_ram().  What do you think?

Cheers,

Tim.

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