Re: [Xen-devel] [RFC 2/2] xen/public: grant-table: Specificy the size of the grant

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.08.15 at 13:28, <julien.grall@xxxxxxxxxx> wrote:
> --- a/xen/include/public/grant_table.h
> +++ b/xen/include/public/grant_table.h
> @@ -51,6 +51,11 @@
>   * know the real machine address of a page it is sharing. This makes
>   * it possible to share memory correctly with domains running in
>   * fully virtualised memory.
> + *
> + * The size of a grant is always 4KB irrespectively of the page
> + * granularity of the guest. This is means that when the guest is using
> + * 64KB page granularity, it will have to split the page in 4KB chunks
> + * and request a grant for every of them.
>   */

This paragraph should get "on ARM" added somewhere. There is no
inherent requirement for such a restriction on another architecture
Xen might get ported to; the only restriction of the current interface
is that it can't support page sizes from 64k up. On an architecture
e.g. not supporting other than 8k pages things would still be fine,
yet the comment above would then be wrong.

An alternative might be to say "... is always the smallest
architecturally supported page size (e.g. 4k on x86 and ARM)
irrespective of ...".

Jan


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