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xen-devel
Re: [Xen-devel] [PATCH] Device duplicate check fix
Hi,
you don't see the need to add this check to xend since the same check is
already present in the hotplug scripts? So, is this useless and should I
do nothing about that and let it be reverted like Keir wrote he did and
do nothing about that?
Michal
Stefano Stabellini wrote:
Sorry for the late reply, but I only now I realized that this patch
breaks stubdoms: an exception is needed to allow a disk to be shared
between the guest and its own stubdom.
Beside I do not see the need to add this check to xend since the same
check is already present in the hotplug scripts.
Michal Novotny wrote:
*Hello,
I've checked the duplicate-check code here and I found that's checked
only in the context of one domain but not cross-domain. The thing is
that we should check tap/vbd device cross-domain not to allow another
guest to use the same disk image in some circumstances to prevent VM's
disk corruption.
The patch included denies disk image addition under those circumstances:
1. **We're adding read-only disk that's already used as write-exclusive
2. **We're adding write-shared disk that's already used as write-exclusive
3. **We're adding write-exclusive disk that's already used
4. **We're adding read-only disk that's already used as write-shared*
(because of I/O caching issues etc.)
*
The vif device duplicate check remains the same it was and it's checked
in the context of current domain only so that behaviour has been preserved.
Michal
Signed-off-by: Michal Novotny <minovotn@xxxxxxxxxx>
*
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