Re: [Xen-devel] [PATCH] [xendomains] Make absolutely certain xendomains won't start a domain that has failed to restore

[Ewan Mellor <ewan@xxxxxxxxxxxxx>]

On Wed, Dec 06, 2006 at 05:40:49PM -0500, Hugh Brock wrote:

> In testing the xendomains init script, we have discovered a condition in
> which xm restore <vm1> will complete successfully, but the xendomains
> script nonetheless attempts to create <vm1> from scratch. Any domain
> with an entry in XENDOMAINS_AUTO that was also automatically paused on
> shutdown is vulnerable to this problem. We believe the sequence of
> events is as follows:
> 
> 1. xm restore guest1
> 2. xend pauses guest1 and waits N seconds for hotplug to complete
> 3. hotplug does not complete (for some reason), so xm restore finishes,
> but guest1 is still in paused state (not destroyed after failure)
> 4. xm create guest1 is run
> 5. original paused guest1 grabs the hotplug devices from the new guest1
> 6. original guest1 is now running
> 7. new guest1 is waiting for devices which were stolen
> 
> This results in a running guest1 and a paused guest1; if an operator
> then attempts to unpause the paused guest1, storage corruption or worse
> could result.
> 
> This patch checks the contents of XENDOMAINS_SAVE before the restore
> process begins, and prevents xendomains from attempting to start any
> domain that appears there, whether the domain started successfully or
> not.
> 
> Signed off by: Hugh Brock <hbrock@xxxxxxxxxx>

Applied, thanks Hugh.

Ewan.

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