ALSA: xen-front: Implement handling of shared buffers

Implement shared buffer handling according to the
para-virtualized sound device protocol at xen/interface/io/sndif.h:
  - manage buffer memory
  - handle granted references
  - handle page directories

[ Fixed missing linux/kernel.h inclusion -- tiwai ]

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/xen/Makefile b/sound/xen/Makefile
index 03c669984000429138cc2c99194f8f2a6fff02f8..f028bc30af5dac6230a6efa65eb2e80a79c16c95 100644 (file)
--- a/sound/xen/Makefile
+++ b/sound/xen/Makefile
@@ -2,6 +2,7 @@
 
 snd_xen_front-objs := xen_snd_front.o \
                      xen_snd_front_cfg.o \
-                     xen_snd_front_evtchnl.o
+                     xen_snd_front_evtchnl.o \
+                     xen_snd_front_shbuf.o
 
 obj-$(CONFIG_SND_XEN_FRONTEND) += snd_xen_front.o

diff --git a/sound/xen/xen_snd_front.c b/sound/xen/xen_snd_front.c
index 277214d4fd0a55a0d1393e7700769974f6c72399..cdf66ea516c456bf11ad0b5d5690a4cfbeadfbab 100644 (file)
--- a/sound/xen/xen_snd_front.c
+++ b/sound/xen/xen_snd_front.c
@@ -11,6 +11,7 @@
 #include <linux/delay.h>
 #include <linux/module.h>
 
+#include <xen/page.h>
 #include <xen/platform_pci.h>
 #include <xen/xen.h>
 #include <xen/xenbus.h>
@@ -191,6 +192,13 @@ static int __init xen_drv_init(void)
        if (!xen_has_pv_devices())
                return -ENODEV;
 
+       /* At the moment we only support case with XEN_PAGE_SIZE == PAGE_SIZE */
+       if (XEN_PAGE_SIZE != PAGE_SIZE) {
+               pr_err(XENSND_DRIVER_NAME ": different kernel and Xen page sizes are not supported: XEN_PAGE_SIZE (%lu) != PAGE_SIZE (%lu)\n",
+                      XEN_PAGE_SIZE, PAGE_SIZE);
+               return -ENODEV;
+       }
+
        pr_info("Initialising Xen " XENSND_DRIVER_NAME " frontend driver\n");
        return xenbus_register_frontend(&xen_driver);
 }

diff --git a/sound/xen/xen_snd_front_shbuf.c b/sound/xen/xen_snd_front_shbuf.c
new file mode 100644 (file)
index 0000000..07ac176
--- /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;
+}

diff --git a/sound/xen/xen_snd_front_shbuf.h b/sound/xen/xen_snd_front_shbuf.h
new file mode 100644 (file)
index 0000000..d28e97c
--- /dev/null
+++ b/sound/xen/xen_snd_front_shbuf.h
@@ -0,0 +1,36 @@
+/* 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>
+ */
+
+#ifndef __XEN_SND_FRONT_SHBUF_H
+#define __XEN_SND_FRONT_SHBUF_H
+
+#include <xen/grant_table.h>
+
+#include "xen_snd_front_evtchnl.h"
+
+struct xen_snd_front_shbuf {
+       int num_grefs;
+       grant_ref_t *grefs;
+       u8 *directory;
+       u8 *buffer;
+       size_t buffer_sz;
+};
+
+grant_ref_t xen_snd_front_shbuf_get_dir_start(struct xen_snd_front_shbuf *buf);
+
+int xen_snd_front_shbuf_alloc(struct xenbus_device *xb_dev,
+                             struct xen_snd_front_shbuf *buf,
+                             unsigned int buffer_sz);
+
+void xen_snd_front_shbuf_clear(struct xen_snd_front_shbuf *buf);
+
+void xen_snd_front_shbuf_free(struct xen_snd_front_shbuf *buf);
+
+#endif /* __XEN_SND_FRONT_SHBUF_H */