Re: [Xen-devel] live migration can fail due to XENMEM_maximum_gpfn

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

On Mon, Oct 06, 2008 at 05:47:53PM +0100, John Levon wrote:
> 
> There's a race that can cause live migration to fail. In particular,
> xc_save uses XENMEM_maximum_gpfn to create the shm segment. qemu then
> also uses that value to look up the segment. However, the value can
> easily change in between due to p2m_set_entry(). In particular if
> there's PV drivers in the HVM domU, ->max_mapped_pfn can change easily:
> 
> dom 11 max gpfn 262143
> dom 11 max gpfn 262143
> dom 11 max gpfn 262143
> ....
> dom 11 max gpfn 985087
> 
> (1Gb Solaris HVM domU).
> 
> I'm not sure how this should be fixed?

I think a similar race would exist once balloon expansion
(using memory hot plug) is implemented.
According to http://wiki.xensource.com/xenwiki/XenParavirtOps,
it is WIP, though.

-- 
yamahata

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