Re: [Xen-devel] [RFC for-4.5 12/12] drivers/passthrough: arm: Add support for SMMU drivers

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hello Jan,

On 20/02/14 08:11, Jan Beulich wrote:
> > > > On 19.02.14 at 18:31, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> > On 02/19/2014 05:27 PM, Ian Campbell wrote:
> > > On Wed, 2014-02-19 at 17:21 +0000, Julien Grall wrote:
> > > > > > +#define SZ_4K                               (1 << 12)
> > > > > > +#define SZ_64K                              (1 << 16)
> > > > > > +
> > > > > > +/* Driver options */
> > > > > > +#define SMMU_OPT_SECURE_CONFIG_ACCESS   (1 << 0)
> > > > > Is this just retained to reduce the deviation from the Linux driver?
> > > > > It's no use to us I think. (I suppose that goes for a bunch of other
> > > > > stuff, eg.. the PGSZ_4K stuff, which I will avoid commenting on
> > > > > further).
> > > > SZ_4K and SZ_64K is used later in the code.
> > > But they are actually useless to us aren't they?
> > As we use only 4K page in Xen yes. I kept it because there is few place
> > where the SMMU configuration is not the same.
> >
> > If we want to support 64K page in the future it will harder to had
> > support if this stuff is removed.
> >
> > The constant was added by himself as it doesn't exists on Xen. I can
> > move it into the generic code.
> But if possible I'd like to encourage you using PAGE_SIZE_4K to
> match up with what we already got in the IOMMU code. Unless
> deviation from the sources you're cloning is deemed worse than
> consistency within our code.
I think this change is fine. It doesn't fundamentally change the code.

I will update the patch for the next version.

Regards,

--
Julien Grall

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