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

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] live migration can fail due to XENMEM_maximum_gpfn
From: John Levon <levon@xxxxxxxxxxxxxxxxx>
Date: Mon, 6 Oct 2008 17:47:53 +0100
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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?

thanks
john

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