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

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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: Julien Grall <julien.grall@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
This commit is contained in:
Julien Grall 2015-06-19 17:49:03 +01:00 committed by David Vrabel
parent 1084b1988d
commit 008c320a96
3 changed files with 69 additions and 1 deletions
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2
arch/x86/include/asm/xen/page.h
View File

@ -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 */

26
drivers/xen/grant-table.c
View File

@ -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)

42
include/xen/grant_table.h
View File

@ -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__ */