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Re: [Xen-devel] [PATCH] Fix restore handling checks

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] [PATCH] Fix restore handling checks
From: Michal Novotny <minovotn@xxxxxxxxxx>
Date: Tue, 22 Jun 2010 08:11:32 +0200
Cc: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
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On 06/22/2010 07:43 AM, Michal Novotny wrote:
On 06/21/2010 08:04 PM, Keir Fraser wrote:
On 21/06/2010 17:30, "Michal Novotny"<minovotn@xxxxxxxxxx>  wrote:

Hi,
this is the patch to fix restore handling to implement some more checks
to support more checks than for UUID and name duplicity. This patch
basically disallows the migration/restore of IDE drives with the
read-only flag since this is not supported according to the ATAPI/IDE
specifications so we should disallow this for both domain creation and
domain migration/restore.
What about CD-ROMs? This would break my test domain config, for example.


Right, there's the exception for CD-ROMs according to the spec. I should implement this as well but read-only IDE disk devices are not supported according to the IDE specs.


This is the updated version of my patch to allow read-only CD-ROM devices as you had a good point that read-only is supported for CD-ROM IDE drives (but only for them).



This patch implements it for both create and
restore/migrate functionality.

Also, the check whether the host machine does have enough memory
available for the guest has been implemented which can be the real issue
when you try to migrate a guest from one machine to another that is not
having enough memory for this guest. The guest memory gets transferred
but it fails to run so it's not running on either of those machines
(i.e. domain is not on the destination nor source host machine).
Failed restore should get reported back to the host that is saving the guest state, and cause that machine to resume execution of the original VM. Does
that not work for you?

Possibly checking up front for available memory on the target is a good
idea, but it shouldn't be *essential* if the error handling is up to par.

  -- Keir


I was able to make it working now and this functionality seems to be working now however I think that the preliminary check before the transfer itself is a good idea. As far as I had it implemented already I just did some modifications to allow CD-ROM IDE read-only drives and this is the updated version.

Michal


I did try it with restore functionality now since I've been able to make
it working for save once so I'm currently using one save image for the
testing but unfortunately I'm having many issues with the common
migration and save functionality since I've been able to make it working
once to save it correctly. Fortunately the restores for this one
particular save image is working fine. I was also thinking about 2
concurrent migrations to the guest and/or save with the concurrent
migration and it should be the issue (although it's not been tested
because of reasons described above) since the domain gets created and
it's available in the XendDomain list (i.e. xc.domain_getinfo() list) so
it shouldn't be an issue here.

Michal

Signed-off-by: Michal Novotny<minovotn@xxxxxxxxxx>





--
Michal Novotny<minovotn@xxxxxxxxxx>, RHCE
Virtualization Team (xen userspace), Red Hat

Attachment: xen-fix-restore-handling-for-ide-drives-and-memory.patch
Description: Text Data

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