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Commit 008c320a authored by Julien Grall's avatar Julien Grall Committed by David Vrabel
Browse files

xen/grant: Introduce helpers to split a page into grant 



Currently, a grant is always based on the Xen page granularity (i.e
4KB). When Linux is using a different page granularity, a single page
will be split between multiple grants.

The new helpers will be in charge of splitting the Linux page into grants
and call a function given by the caller on each grant.

Also provide an helper to count the number of grants within a given
contiguous region.

Note that the x86/include/asm/xen/page.h is now including
xen/interface/grant_table.h rather than xen/grant_table.h. It's
necessary because xen/grant_table.h depends on asm/xen/page.h and will
break the compilation. Furthermore, only definition in
interface/grant_table.h is required.

Signed-off-by: default avatarJulien Grall <julien.grall@citrix.com>
Reviewed-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
Reviewed-by: default avatarStefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
parent 1084b198

arch/x86/include/asm/xen/page.h

+1 −1
Original line number Diff line number Diff line
@@ -12,7 +12,7 @@ 
#include <asm/pgtable.h>



#include <xen/interface/xen.h>

#include <xen/grant_table.h>

#include <xen/interface/grant_table.h>

#include <xen/features.h>



/* Xen machine address */

drivers/xen/grant-table.c

+26 −0
Original line number Diff line number Diff line
@@ -776,6 +776,32 @@ void gnttab_batch_copy(struct gnttab_copy *batch, unsigned count) 
}

EXPORT_SYMBOL_GPL(gnttab_batch_copy);



void gnttab_foreach_grant_in_range(struct page *page,

				   unsigned int offset,

				   unsigned int len,

				   xen_grant_fn_t fn,

				   void *data)

{

	unsigned int goffset;

	unsigned int glen;

	unsigned long xen_pfn;



	len = min_t(unsigned int, PAGE_SIZE - offset, len);

	goffset = xen_offset_in_page(offset);



	xen_pfn = page_to_xen_pfn(page) + XEN_PFN_DOWN(offset);



	while (len) {

		glen = min_t(unsigned int, XEN_PAGE_SIZE - goffset, len);

		fn(pfn_to_gfn(xen_pfn), goffset, glen, data);



		goffset = 0;

		xen_pfn++;

		len -= glen;

	}

}

EXPORT_SYMBOL_GPL(gnttab_foreach_grant_in_range);



int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,

		    struct gnttab_map_grant_ref *kmap_ops,

		    struct page **pages, unsigned int count)

include/xen/grant_table.h

+42 −0
Original line number Diff line number Diff line
@@ -45,8 +45,10 @@ 
#include <asm/xen/hypervisor.h>



#include <xen/features.h>

#include <xen/page.h>

#include <linux/mm_types.h>

#include <linux/page-flags.h>

#include <linux/kernel.h>



#define GNTTAB_RESERVED_XENSTORE 1
@@ -224,4 +226,44 @@ static inline struct xen_page_foreign *xen_page_foreign(struct page *page) 
#endif

}



/* Split Linux page in chunk of the size of the grant and call fn

 *

 * Parameters of fn:

 *	gfn: guest frame number

 *	offset: offset in the grant

 *	len: length of the data in the grant.

 *	data: internal information

 */

typedef void (*xen_grant_fn_t)(unsigned long gfn, unsigned int offset,

			       unsigned int len, void *data);



void gnttab_foreach_grant_in_range(struct page *page,

				   unsigned int offset,

				   unsigned int len,

				   xen_grant_fn_t fn,

				   void *data);



/* Helper to get to call fn only on the first "grant chunk" */

static inline void gnttab_for_one_grant(struct page *page, unsigned int offset,

					unsigned len, xen_grant_fn_t fn,

					void *data)

{

	/* The first request is limited to the size of one grant */

	len = min_t(unsigned int, XEN_PAGE_SIZE - (offset & ~XEN_PAGE_MASK),

		    len);



	gnttab_foreach_grant_in_range(page, offset, len, fn, data);

}



/* Get the number of grant in a specified region

 *

 * start: Offset from the beginning of the first page

 * len: total length of data (can cross multiple page)

 */

static inline unsigned int gnttab_count_grant(unsigned int start,

					      unsigned int len)

{

	return XEN_PFN_UP(xen_offset_in_page(start) + len);

}



#endif /* __ASM_GNTTAB_H__ */