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authorJuergen Gross <jgross@suse.com>2022-04-28 09:01:03 +0200
committerJuergen Gross <jgross@suse.com>2022-05-19 14:21:55 +0200
commit7050096d07755c53f71e486af18475050cc4e04b (patch)
treed349d6a8581287ad96ceb2c563adc2ecc0ef4f5a /drivers/xen
parent6fac592cca60dca0b2a524c303c83e958c2003bb (diff)
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>
Diffstat (limited to 'drivers/xen')
-rw-r--r--drivers/xen/xenbus/xenbus_client.c69
1 files changed, 69 insertions, 0 deletions
diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index df6890681231..1a2e0d94ccd1 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -407,6 +407,75 @@ int xenbus_grant_ring(struct xenbus_device *dev, void *vaddr,
}
EXPORT_SYMBOL_GPL(xenbus_grant_ring);
+/*
+ * xenbus_setup_ring
+ * @dev: xenbus device
+ * @vaddr: pointer to starting virtual address of the ring
+ * @nr_pages: number of pages to be granted
+ * @grefs: grant reference array to be filled in
+ *
+ * Allocate physically contiguous pages for a shared ring buffer and grant it
+ * to the peer of the given device. The ring buffer is initially filled with
+ * zeroes. The virtual address of the ring is stored at @vaddr and the
+ * grant references are stored in the @grefs array. In case of error @vaddr
+ * will be set to NULL and @grefs will be filled with INVALID_GRANT_REF.
+ */
+int xenbus_setup_ring(struct xenbus_device *dev, gfp_t gfp, void **vaddr,
+ unsigned int nr_pages, grant_ref_t *grefs)
+{
+ unsigned long ring_size = nr_pages * XEN_PAGE_SIZE;
+ unsigned int i;
+ int ret;
+
+ *vaddr = alloc_pages_exact(ring_size, gfp | __GFP_ZERO);
+ if (!*vaddr) {
+ ret = -ENOMEM;
+ goto err;
+ }
+
+ ret = xenbus_grant_ring(dev, *vaddr, nr_pages, grefs);
+ if (ret)
+ goto err;
+
+ return 0;
+
+ err:
+ if (*vaddr)
+ free_pages_exact(*vaddr, ring_size);
+ for (i = 0; i < nr_pages; i++)
+ grefs[i] = INVALID_GRANT_REF;
+ *vaddr = NULL;
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(xenbus_setup_ring);
+
+/*
+ * xenbus_teardown_ring
+ * @vaddr: starting virtual address of the ring
+ * @nr_pages: number of pages
+ * @grefs: grant reference array
+ *
+ * Remove grants for the shared ring buffer and free the associated memory.
+ * On return the grant reference array is filled with INVALID_GRANT_REF.
+ */
+void xenbus_teardown_ring(void **vaddr, unsigned int nr_pages,
+ grant_ref_t *grefs)
+{
+ unsigned int i;
+
+ for (i = 0; i < nr_pages; i++) {
+ if (grefs[i] != INVALID_GRANT_REF) {
+ gnttab_end_foreign_access(grefs[i], 0);
+ grefs[i] = INVALID_GRANT_REF;
+ }
+ }
+
+ if (*vaddr)
+ free_pages_exact(*vaddr, nr_pages * XEN_PAGE_SIZE);
+ *vaddr = NULL;
+}
+EXPORT_SYMBOL_GPL(xenbus_teardown_ring);
/**
* Allocate an event channel for the given xenbus_device, assigning the newly