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Re: [Xen-devel] [PATCH] Fix bug #331

To: Ewan Mellor <ewan@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Fix bug #331
From: Dan Smith <danms@xxxxxxxxxx>
Date: Fri, 25 Nov 2005 15:55:37 -0800
Cc: Xen Developers <xen-devel@xxxxxxxxxxxxxxxxxxx>
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EM> Unfortunately, Xend is not the right place for these checks.  We
EM> have to worry about device configuration even when it's not
EM> performed through Xend -- the drivers will configure the device if
EM> you write to the store, even if you don't go through Xend.  With
EM> that in mind, these safety checks need to be lower down in the
EM> system. 

I think the drivers should attach multiple DomUs to the same block
device, if asked to do so.  The bug description said that this
functionality should be provided by the tools for special-purpose
filesystems that can handle concurrent writers.  It seems perfectly
logical to me for the drivers to do what they're told, and have the
tools (whatever tools may be in use) provide the checks and
protections necessary to help the user from shooting himself in the
foot.

Further, I think that pushing a bunch of checks into the hotplug
scripts is less desirable, as it makes it harder to communicate good
information back to the frontend tools.  Right now, we just get a
"failed" message instead of "device missing" or "device already in
use" message.

-- 
Dan Smith
IBM Linux Technology Center
Open Hypervisor Team
email: danms@xxxxxxxxxx


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