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Re: [Xen-devel] Occasional clock/time problems on HVM domU after live migrate on Xen 4.2.{1, 2}

On Sat, 2013-04-27 at 18:11 +0100, Alex Bligh wrote:
> I am seeing occasional clock/time problems on an HVM domU with upstream 
> qemu-dm on Xen 4.2 (more precisely 4.2.2-rc1 with my live migrate
> patches).

Does this work with Xen unstable? (IOW can we isolate this to an
upstream bug or a backporting bug/lack of a fix)

> I'm migrating between two machines with identical hardware. I'm using an
> Ubuntu Precise dom0 and domU. The machines run ntp in dom0 for what its
> worth, but their RTCs may not be synced.
> When I migrate a machine in one direction it very frequently works. However,
> sometimes, executing a ping command on the migrated machine appears to fail.
> Close inspection suggests the networking works (I can see traffic going in
> and out), but the machine's idea of time is all screwed up so ping gets
> confused into sending nothing. It's as if time is not moving forward on
> the migrated machine.
> Possibly for a similar reason, the paravirtualised domU vNIC which is
> attached to a bridge in dom0 sometimes comes up 'NO CARRIER' for no
> discernable reason. It appears to be a member of the relevant bridge
> according to brctl. I'm not sure how the pv nic detects the presence
> of 'carrier'.
> Any ideas?

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