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

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 */

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

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.


Julien Grall

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