Re: [Xen-devel] [PATCH] Device duplicate check fix

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

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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