Xen devel - Nov 2009 - why would XENMEM_decrease_reservation fail?

I am attempting to implement the kludge to make save/restore/migrate
work in the GPLPV drivers under Xen 3.4.1. On my test box I successfully
free grant_table_pages + 1 pages. The logs from another users system
show that each call to XENMEM_decrease_reservation returns 0 instead of
1.

Under what circumstances would XENMEM_decrease_reservation fail? The pfn
passed to XENMEM_decrease_reservation looks reasonable (similar values
to my test box), and everything else is identical.

Thanks

James


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On 16/11/2009 22:52, "James Harper"
<james.harper@bendigoit.com.au> wrote:
> I am attempting to implement the kludge to make save/restore/migrate
> work in the GPLPV drivers under Xen 3.4.1. On my test box I successfully
> free grant_table_pages + 1 pages. The logs from another users system
> show that each call to XENMEM_decrease_reservation returns 0 instead of
> 1.
> 
> Under what circumstances would XENMEM_decrease_reservation fail? The pfn
> passed to XENMEM_decrease_reservation looks reasonable (similar values
> to my test box), and everything else is identical.
Really it should only fail if the page does not belong to the guest. You
might have to give them a patch to add tracing to error paths in e.g.,
guest_remove_page() to find out what''s going on, if this happens
deterministically for them.

 -- Keir



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