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Commit d6e0fbb8 authored by Oleksandr Andrushchenko's avatar Oleksandr Andrushchenko Committed by Takashi Iwai
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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: default avatarOleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 788ef64a

sound/xen/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -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

sound/xen/xen_snd_front.c

+8 −0
Original line number Diff line number Diff line
@@ -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);

}

sound/xen/xen_snd_front_shbuf.c

0 → 100644
+194 −0
Original line number Diff line number Diff line 
// 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;

}

sound/xen/xen_snd_front_shbuf.h

0 → 100644
+36 −0
Original line number Diff line number Diff line 
/* 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 */