[Xen-devel] [PATCH v2 02/20] xen: Introduce a function to split a Linux page into Xen page

David Vrabel david.vrabel at citrix.com
Fri Jul 24 02:31:39 PDT 2015

On 09/07/15 21:42, Julien Grall wrote:
> The Xen interface is always using 4KB page. This means that a Linux page
> may be split across multiple Xen page when the page granularity is not
> the same.
> This helper will break down a Linux page into 4KB chunk and call the
> helper on each of them.
> --- a/include/xen/page.h
> +++ b/include/xen/page.h
> @@ -39,4 +39,24 @@ struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS];
>  extern unsigned long xen_released_pages;
> +typedef int (*xen_pfn_fn_t)(struct page *page, unsigned long pfn, void *data);
> +
> +/* Break down the page in 4KB granularity and call fn foreach xen pfn */
> +static inline int xen_apply_to_page(struct page *page, xen_pfn_fn_t fn,
> +				    void *data)

I think this should be outlined (unless you have measurements that
support making it inlined).

Also perhaps make it

int xen_for_each_gfn(struct page *page,
                     xen_gfn_fn_t fn, void *data);


int xen_for_each_gfn(struct page **page, unsigned int count,
                     xen_gfn_fn_t fn, void *data);



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