Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
xen/xenbus: add xenbus_setup_ring() service function
Most PV device frontends share very similar code for setting up shared
ring buffers:
- allocate page(s)
- init the ring admin data
- give the backend access to the ring via grants
Tearing down the ring requires similar actions in all frontends again:
- remove grants
- free the page(s)
Provide service functions xenbus_setup_ring() and xenbus_teardown_ring()
for that purpose.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
+73
+69
drivers/xen/xenbus/xenbus_client.c
+69
drivers/xen/xenbus/xenbus_client.c
···
407
407
}
408
408
EXPORT_SYMBOL_GPL(xenbus_grant_ring);
409
409
410
+
/*
411
+
* xenbus_setup_ring
412
+
* @dev: xenbus device
413
+
* @vaddr: pointer to starting virtual address of the ring
414
+
* @nr_pages: number of pages to be granted
415
+
* @grefs: grant reference array to be filled in
416
+
*
417
+
* Allocate physically contiguous pages for a shared ring buffer and grant it
418
+
* to the peer of the given device. The ring buffer is initially filled with
419
+
* zeroes. The virtual address of the ring is stored at @vaddr and the
420
+
* grant references are stored in the @grefs array. In case of error @vaddr
421
+
* will be set to NULL and @grefs will be filled with INVALID_GRANT_REF.
422
+
*/
423
+
int xenbus_setup_ring(struct xenbus_device *dev, gfp_t gfp, void **vaddr,
424
+
unsigned int nr_pages, grant_ref_t *grefs)
425
+
{
426
+
unsigned long ring_size = nr_pages * XEN_PAGE_SIZE;
427
+
unsigned int i;
428
+
int ret;
429
+
430
+
*vaddr = alloc_pages_exact(ring_size, gfp | __GFP_ZERO);
431
+
if (!*vaddr) {
432
+
ret = -ENOMEM;
433
+
goto err;
434
+
}
435
+
436
+
ret = xenbus_grant_ring(dev, *vaddr, nr_pages, grefs);
437
+
if (ret)
438
+
goto err;
439
+
440
+
return 0;
441
+
442
+
err:
443
+
if (*vaddr)
444
+
free_pages_exact(*vaddr, ring_size);
445
+
for (i = 0; i < nr_pages; i++)
446
+
grefs[i] = INVALID_GRANT_REF;
447
+
*vaddr = NULL;
448
+
449
+
return ret;
450
+
}
451
+
EXPORT_SYMBOL_GPL(xenbus_setup_ring);
452
+
453
+
/*
454
+
* xenbus_teardown_ring
455
+
* @vaddr: starting virtual address of the ring
456
+
* @nr_pages: number of pages
457
+
* @grefs: grant reference array
458
+
*
459
+
* Remove grants for the shared ring buffer and free the associated memory.
460
+
* On return the grant reference array is filled with INVALID_GRANT_REF.
461
+
*/
462
+
void xenbus_teardown_ring(void **vaddr, unsigned int nr_pages,
463
+
grant_ref_t *grefs)
464
+
{
465
+
unsigned int i;
466
+
467
+
for (i = 0; i < nr_pages; i++) {
468
+
if (grefs[i] != INVALID_GRANT_REF) {
469
+
gnttab_end_foreign_access(grefs[i], 0);
470
+
grefs[i] = INVALID_GRANT_REF;
471
+
}
472
+
}
473
+
474
+
if (*vaddr)
475
+
free_pages_exact(*vaddr, nr_pages * XEN_PAGE_SIZE);
476
+
*vaddr = NULL;
477
+
}
478
+
EXPORT_SYMBOL_GPL(xenbus_teardown_ring);
410
479
411
480
/**
412
481
* Allocate an event channel for the given xenbus_device, assigning the newly
+4
include/xen/xenbus.h
+4
include/xen/xenbus.h
···
226
226
int xenbus_switch_state(struct xenbus_device *dev, enum xenbus_state new_state);
227
227
int xenbus_grant_ring(struct xenbus_device *dev, void *vaddr,
228
228
unsigned int nr_pages, grant_ref_t *grefs);
229
+
int xenbus_setup_ring(struct xenbus_device *dev, gfp_t gfp, void **vaddr,
230
+
unsigned int nr_pages, grant_ref_t *grefs);
231
+
void xenbus_teardown_ring(void **vaddr, unsigned int nr_pages,
232
+
grant_ref_t *grefs);
229
233
int xenbus_map_ring_valloc(struct xenbus_device *dev, grant_ref_t *gnt_refs,
230
234
unsigned int nr_grefs, void **vaddr);
231
235