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Re: [Xen-devel] [PATCH v3 05/13] xen/iommu: arm: Remove temporary the SMMU driver

On Fri, 2015-02-20 at 12:53 +0000, Julien Grall wrote:
> Hi Ian,
> On 20/02/15 12:18, Ian Campbell wrote:
> > On Fri, 2015-01-30 at 18:49 +0000, Julien Grall wrote:
> >> The current SMMU driver has completly diverged. That makes me hard to
> >> maintain.
> > 
> > Will this temporarily regress anything in a noticeable way? I think
> > it'll just potentially make some hypothetical platform switch back to
> > 1:1 dom0 mode, which in practice they all use anyway, IOW no harm done,
> > even temporarily. So:
> We still have to keep the 1:1 DOM0 mapping with SMMU. It's because we
> don't know if all devices are protected.
> The only possible regression is the SMMU node won't be remove from DOM0
> and threfore may be used by Linux. Aside that there is no different for
> the user.

Might that cause issues?

The main thing I'm worried about is if the bisector is searching a range
which includes this change looking for some unrelated change and this
commit causes some sort of spurious issue or perturbation which confuses
the bisector.

Perhaps a temporary stub could be put in which just marks SMMUs as used
by Xen but doesn't actually use them?

> >> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> >> Acked-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > 
> > Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Regards,

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