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Re: [PATCH 09/18] xen/xenbus: add xenbus_setup_ring() service function
- To: Juergen Gross <jgross@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
- From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
- Date: Wed, 20 Apr 2022 14:44:31 -0400
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
- Delivery-date: Wed, 20 Apr 2022 18:45:06 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 4/20/22 11:09 AM, Juergen Gross wrote:
+/*
+ * 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;
+}
We can create a wrapper around this function that will also call
SHARED_RING_INIT() and FRONT_RING_INIT(). A bunch of drivers do that.
-boris
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