1 files changed, 194 insertions, 0 deletions

diff --git a/sound/xen/xen_snd_front_shbuf.c b/sound/xen/xen_snd_front_shbuf.c
new file mode 100644
index 000000000000..07ac176a41ba
--- /dev/null
+++ b/sound/xen/xen_snd_front_shbuf.c
@@ -0,0 +1,194 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+/*
+ * Xen para-virtual sound device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#include <linux/kernel.h>
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+
+#include "xen_snd_front_shbuf.h"
+
+grant_ref_t xen_snd_front_shbuf_get_dir_start(struct xen_snd_front_shbuf *buf)
+{
+        if (!buf->grefs)
+                return GRANT_INVALID_REF;
+
+        return buf->grefs[0];
+}
+
+void xen_snd_front_shbuf_clear(struct xen_snd_front_shbuf *buf)
+{
+        memset(buf, 0, sizeof(*buf));
+}
+
+void xen_snd_front_shbuf_free(struct xen_snd_front_shbuf *buf)
+{
+        int i;
+
+        if (buf->grefs) {
+                for (i = 0; i < buf->num_grefs; i++)
+                        if (buf->grefs[i] != GRANT_INVALID_REF)
+                                gnttab_end_foreign_access(buf->grefs[i],
+                                                          0, 0UL);
+                kfree(buf->grefs);
+        }
+        kfree(buf->directory);
+        free_pages_exact(buf->buffer, buf->buffer_sz);
+        xen_snd_front_shbuf_clear(buf);
+}
+
+/*
+ * number of grant references a page can hold with respect to the
+ * xensnd_page_directory header
+ */
+#define XENSND_NUM_GREFS_PER_PAGE ((XEN_PAGE_SIZE - \
+                offsetof(struct xensnd_page_directory, gref)) / \
+                sizeof(grant_ref_t))
+
+static void fill_page_dir(struct xen_snd_front_shbuf *buf,
+                          int num_pages_dir)
+{
+        struct xensnd_page_directory *page_dir;
+        unsigned char *ptr;
+        int i, cur_gref, grefs_left, to_copy;
+
+        ptr = buf->directory;
+        grefs_left = buf->num_grefs - num_pages_dir;
+        /*
+         * skip grant references at the beginning, they are for pages granted
+         * for the page directory itself
+         */
+        cur_gref = num_pages_dir;
+        for (i = 0; i < num_pages_dir; i++) {
+                page_dir = (struct xensnd_page_directory *)ptr;
+                if (grefs_left <= XENSND_NUM_GREFS_PER_PAGE) {
+                        to_copy = grefs_left;
+                        page_dir->gref_dir_next_page = GRANT_INVALID_REF;
+                } else {
+                        to_copy = XENSND_NUM_GREFS_PER_PAGE;
+                        page_dir->gref_dir_next_page = buf->grefs[i + 1];
+                }
+
+                memcpy(&page_dir->gref, &buf->grefs[cur_gref],
+                       to_copy * sizeof(grant_ref_t));
+
+                ptr += XEN_PAGE_SIZE;
+                grefs_left -= to_copy;
+                cur_gref += to_copy;
+        }
+}
+
+static int grant_references(struct xenbus_device *xb_dev,
+                            struct xen_snd_front_shbuf *buf,
+                            int num_pages_dir, int num_pages_buffer,
+                            int num_grefs)
+{
+        grant_ref_t priv_gref_head;
+        unsigned long frame;
+        int ret, i, j, cur_ref;
+        int otherend_id;
+
+        ret = gnttab_alloc_grant_references(num_grefs, &priv_gref_head);
+        if (ret)
+                return ret;
+
+        buf->num_grefs = num_grefs;
+        otherend_id = xb_dev->otherend_id;
+        j = 0;
+
+        for (i = 0; i < num_pages_dir; i++) {
+                cur_ref = gnttab_claim_grant_reference(&priv_gref_head);
+                if (cur_ref < 0) {
+                        ret = cur_ref;
+                        goto fail;
+                }
+
+                frame = xen_page_to_gfn(virt_to_page(buf->directory +
+                                                     XEN_PAGE_SIZE * i));
+                gnttab_grant_foreign_access_ref(cur_ref, otherend_id, frame, 0);
+                buf->grefs[j++] = cur_ref;
+        }
+
+        for (i = 0; i < num_pages_buffer; i++) {
+                cur_ref = gnttab_claim_grant_reference(&priv_gref_head);
+                if (cur_ref < 0) {
+                        ret = cur_ref;
+                        goto fail;
+                }
+
+                frame = xen_page_to_gfn(virt_to_page(buf->buffer +
+                                                     XEN_PAGE_SIZE * i));
+                gnttab_grant_foreign_access_ref(cur_ref, otherend_id, frame, 0);
+                buf->grefs[j++] = cur_ref;
+        }
+
+        gnttab_free_grant_references(priv_gref_head);
+        fill_page_dir(buf, num_pages_dir);
+        return 0;
+
+fail:
+        gnttab_free_grant_references(priv_gref_head);
+        return ret;
+}
+
+static int alloc_int_buffers(struct xen_snd_front_shbuf *buf,
+                             int num_pages_dir, int num_pages_buffer,
+                             int num_grefs)
+{
+        buf->grefs = kcalloc(num_grefs, sizeof(*buf->grefs), GFP_KERNEL);
+        if (!buf->grefs)
+                return -ENOMEM;
+
+        buf->directory = kcalloc(num_pages_dir, XEN_PAGE_SIZE, GFP_KERNEL);
+        if (!buf->directory)
+                goto fail;
+
+        buf->buffer_sz = num_pages_buffer * XEN_PAGE_SIZE;
+        buf->buffer = alloc_pages_exact(buf->buffer_sz, GFP_KERNEL);
+        if (!buf->buffer)
+                goto fail;
+
+        return 0;
+
+fail:
+        kfree(buf->grefs);
+        buf->grefs = NULL;
+        kfree(buf->directory);
+        buf->directory = NULL;
+        return -ENOMEM;
+}
+
+int xen_snd_front_shbuf_alloc(struct xenbus_device *xb_dev,
+                              struct xen_snd_front_shbuf *buf,
+                              unsigned int buffer_sz)
+{
+        int num_pages_buffer, num_pages_dir, num_grefs;
+        int ret;
+
+        xen_snd_front_shbuf_clear(buf);
+
+        num_pages_buffer = DIV_ROUND_UP(buffer_sz, XEN_PAGE_SIZE);
+        /* number of pages the page directory consumes itself */
+        num_pages_dir = DIV_ROUND_UP(num_pages_buffer,
+                                     XENSND_NUM_GREFS_PER_PAGE);
+        num_grefs = num_pages_buffer + num_pages_dir;
+
+        ret = alloc_int_buffers(buf, num_pages_dir,
+                                num_pages_buffer, num_grefs);
+        if (ret < 0)
+                return ret;
+
+        ret = grant_references(xb_dev, buf, num_pages_dir, num_pages_buffer,
+                               num_grefs);
+        if (ret < 0)
+                return ret;
+
+        fill_page_dir(buf, num_pages_dir);
+        return 0;
+}