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Re: [libvirt] [PATCH 2/2] qemu: Clear source path of removable block if it is ejected.



[ CC to Markus and Luiz ]

于 2011年08月12日 22:00, Daniel P. Berrange 写道:
On Fri, Aug 12, 2011 at 09:14:09PM +0800, Osier Yang wrote:
于 2011年08月12日 21:04, Daniel P. Berrange 写道:
   The changes affect the running domain config, (e.g. for a running
domain, "virsh dumpxml" won't display the source path of the media
anymore once it's ejected inside guest. But think it's reasonable
to do like so.
No, IMHO, we really do not want to be going to the QEMU monitor every
time we dump XML. We want the dump XML operation to be fast&   reliable
even in the face of a stuck/deadlocked QEMU [1].

If we want Dump XML to always show the corect state, then we need
QEMU to be giving us an event notification.


Daniel

[1] Yes we have a problem with the balloon query update in this respect
     too, but we need to fix that, not make the problem worse.
Agree, but there is no better idea in my mind to solve the migration
problem with
"info block" but no qemu event.

Both the public migration APIs and the internal qemu migration APIs
need to get
the domain XML before doing preparation on dest host, all of them
need a way to
let the dest known if the disk is ejected. That's why I choosed to change
"qemuDomainFormatXML".
I see the problem is that with the v2 migration protocol, we simply
call into the normal  virDomainGetXMLDesc API call. This was fixed
in v3 migration to use the virDomainMigrateBegin call to get the
XML.

Or do you have any good idea? Thanks
I really think we should invest our time in getting QEMU to provide us
with event notifications, rather than trying to hack around it by using
info block. It really shouldn't be this hard to get an event from QEMU
when they already have the data we need.

Daniel

Hi Markus and Luiz,

As the discussion in this thread, we have problem on solving the problem with just "info block" but no event. Do you think it's acceptable for qemu upstream
to add the event support? I can invest time on doing the work if need.

Thanks
Osier


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