[Xen-devel] [RFC 12/23] xen: Extend page_to_mfn to take an offset in the page

Hi David,

On 19/05/15 14:57, David Vrabel wrote:

On 14/05/15 18:00, Julien Grall wrote:

quoted

With 64KB page granularity support in Linux, a page will be split accross
multiple MFN (Xen is using 4KB page granularity). Thoses MFNs may not be
contiguous.

With the offset in the page, the helper will be able to know which MFN
the driver needs to retrieve.

I think a gnttab_grant_foreign_access_ref()-like helper that takes a
page would be better.

You will probably want this helper able to return/fill a set of refs for
64 KiB pages.

I will see what I can do.

Although, I think this patch is still valid to avoid wrong usage with
64KB page granularity by the caller.

The developer may think that MFN are contiguous which is not always true.

Regards,

-- 
Julien Grall