Release 4.7 drivers/hv/ring_buffer.c

/*
 *
 * Copyright (c) 2009, Microsoft Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place - Suite 330, Boston, MA 02111-1307 USA.
 *
 * Authors:
 *   Haiyang Zhang <haiyangz@microsoft.com>
 *   Hank Janssen  <hjanssen@microsoft.com>
 *   K. Y. Srinivasan <kys@microsoft.com>
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/hyperv.h>
#include <linux/uio.h>

#include "hyperv_vmbus.h"



void hv_begin_read(struct hv_ring_buffer_info *rbi)
{
	rbi->ring_buffer->interrupt_mask = 1;
	virt_mb();
}

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u32 hv_end_read(struct hv_ring_buffer_info *rbi)
{

	rbi->ring_buffer->interrupt_mask = 0;
	virt_mb();

	/*
         * Now check to see if the ring buffer is still empty.
         * If it is not, we raced and we need to process new
         * incoming messages.
         */
	return hv_get_bytes_to_read(rbi);
}

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/*
 * When we write to the ring buffer, check if the host needs to
 * be signaled. Here is the details of this protocol:
 *
 *      1. The host guarantees that while it is draining the
 *         ring buffer, it will set the interrupt_mask to
 *         indicate it does not need to be interrupted when
 *         new data is placed.
 *
 *      2. The host guarantees that it will completely drain
 *         the ring buffer before exiting the read loop. Further,
 *         once the ring buffer is empty, it will clear the
 *         interrupt_mask and re-check to see if new data has
 *         arrived.
 */



static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)
{
	virt_mb();
	if (READ_ONCE(rbi->ring_buffer->interrupt_mask))
		return false;

	/* check interrupt_mask before read_index */
	virt_rmb();
	/*
         * This is the only case we need to signal when the
         * ring transitions from being empty to non-empty.
         */
	if (old_write == READ_ONCE(rbi->ring_buffer->read_index))
		return true;

	return false;
}

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/* Get the next write location for the specified ring buffer. */

static inline u32

hv_get_next_write_location(struct hv_ring_buffer_info *ring_info)
{
	u32 next = ring_info->ring_buffer->write_index;

	return next;
}

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/* Set the next write location for the specified ring buffer. */

static inline void

hv_set_next_write_location(struct hv_ring_buffer_info *ring_info,
		     u32 next_write_location)
{
	ring_info->ring_buffer->write_index = next_write_location;
}

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haiyang zhang
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26.09%
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greg kroah-hartman
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/* Get the next read location for the specified ring buffer. */

static inline u32

hv_get_next_read_location(struct hv_ring_buffer_info *ring_info)
{
	u32 next = ring_info->ring_buffer->read_index;

	return next;
}

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/*
 * Get the next read location + offset for the specified ring buffer.
 * This allows the caller to skip.
 */

static inline u32

hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info,
				 u32 offset)
{
	u32 next = ring_info->ring_buffer->read_index;

	next += offset;
	next %= ring_info->ring_datasize;

	return next;
}

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21.62%
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/* Set the next read location for the specified ring buffer. */

static inline void

hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
		    u32 next_read_location)
{
	ring_info->ring_buffer->read_index = next_read_location;
	ring_info->priv_read_index = next_read_location;
}

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/* Get the size of the ring buffer. */

static inline u32

hv_get_ring_buffersize(struct hv_ring_buffer_info *ring_info)
{
	return ring_info->ring_datasize;
}

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/* Get the read and write indices as u64 of the specified ring buffer. */

static inline u64

hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info)
{
	return (u64)ring_info->ring_buffer->write_index << 32;
}

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33.33%
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/*
 * Helper routine to copy to source from ring buffer.
 * Assume there is enough room. Handles wrap-around in src case only!!
 */


static u32 hv_copyfrom_ringbuffer(
	struct hv_ring_buffer_info	*ring_info,
	void				*dest,
	u32				destlen,
	u32				start_read_offset)
{
	void *ring_buffer = hv_get_ring_buffer(ring_info);
	u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);

	u32 frag_len;

	/* wrap-around detected at the src */
	if (destlen > ring_buffer_size - start_read_offset) {
		frag_len = ring_buffer_size - start_read_offset;

		memcpy(dest, ring_buffer + start_read_offset, frag_len);
		memcpy(dest + frag_len, ring_buffer, destlen - frag_len);
	} else

		memcpy(dest, ring_buffer + start_read_offset, destlen);


	start_read_offset += destlen;
	start_read_offset %= ring_buffer_size;

	return start_read_offset;
}


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/*
 * Helper routine to copy from source to ring buffer.
 * Assume there is enough room. Handles wrap-around in dest case only!!
 */


static u32 hv_copyto_ringbuffer(
	struct hv_ring_buffer_info	*ring_info,
	u32				start_write_offset,
	void				*src,
	u32				srclen)
{
	void *ring_buffer = hv_get_ring_buffer(ring_info);
	u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
	u32 frag_len;

	/* wrap-around detected! */
	if (srclen > ring_buffer_size - start_write_offset) {
		frag_len = ring_buffer_size - start_write_offset;
		memcpy(ring_buffer + start_write_offset, src, frag_len);
		memcpy(ring_buffer, src + frag_len, srclen - frag_len);
	} else
		memcpy(ring_buffer + start_write_offset, src, srclen);

	start_write_offset += srclen;
	start_write_offset %= ring_buffer_size;

	return start_write_offset;
}

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greg kroah-hartman
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5.71%
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42.86%
hank janssen
hank janssen
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/* Get various debug metrics for the specified ring buffer. */


void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
			    struct hv_ring_buffer_debug_info *debug_info)
{
	u32 bytes_avail_towrite;
	u32 bytes_avail_toread;

	if (ring_info->ring_buffer) {
		hv_get_ringbuffer_availbytes(ring_info,
					&bytes_avail_toread,
					&bytes_avail_towrite);

		debug_info->bytes_avail_toread = bytes_avail_toread;
		debug_info->bytes_avail_towrite = bytes_avail_towrite;
		debug_info->current_read_index =
			ring_info->ring_buffer->read_index;
		debug_info->current_write_index =
			ring_info->ring_buffer->write_index;
		debug_info->current_interrupt_mask =
			ring_info->ring_buffer->interrupt_mask;
	}
}

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/* Initialize the ring buffer. */


int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
		   void *buffer, u32 buflen)
{
	if (sizeof(struct hv_ring_buffer) != PAGE_SIZE)
		return -EINVAL;

	memset(ring_info, 0, sizeof(struct hv_ring_buffer_info));

	ring_info->ring_buffer = (struct hv_ring_buffer *)buffer;
	ring_info->ring_buffer->read_index =
		ring_info->ring_buffer->write_index = 0;

	/* Set the feature bit for enabling flow control. */
	ring_info->ring_buffer->feature_bits.value = 1;

	ring_info->ring_size = buflen;
	ring_info->ring_datasize = buflen - sizeof(struct hv_ring_buffer);

	spin_lock_init(&ring_info->ring_lock);

	return 0;
}

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vitaly kuznetsov
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/* Cleanup the ring buffer. */


void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
{
}

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/* Write to the ring buffer. */


int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
		    struct kvec *kv_list, u32 kv_count, bool *signal, bool lock)
{
	int i = 0;
	u32 bytes_avail_towrite;
	u32 totalbytes_towrite = 0;

	u32 next_write_location;
	u32 old_write;
	u64 prev_indices = 0;
	unsigned long flags = 0;

	for (i = 0; i < kv_count; i++)
		totalbytes_towrite += kv_list[i].iov_len;

	totalbytes_towrite += sizeof(u64);

	if (lock)
		spin_lock_irqsave(&outring_info->ring_lock, flags);

	bytes_avail_towrite = hv_get_bytes_to_write(outring_info);

	/*
         * If there is only room for the packet, assume it is full.
         * Otherwise, the next time around, we think the ring buffer
         * is empty since the read index == write index.
         */
	if (bytes_avail_towrite <= totalbytes_towrite) {
		if (lock)
			spin_unlock_irqrestore(&outring_info->ring_lock, flags);
		return -EAGAIN;
	}

	/* Write to the ring buffer */
	next_write_location = hv_get_next_write_location(outring_info);

	old_write = next_write_location;

	for (i = 0; i < kv_count; i++) {
		next_write_location = hv_copyto_ringbuffer(outring_info,
						     next_write_location,
						     kv_list[i].iov_base,
						     kv_list[i].iov_len);
	}

	/* Set previous packet start */
	prev_indices = hv_get_ring_bufferindices(outring_info);

	next_write_location = hv_copyto_ringbuffer(outring_info,
					     next_write_location,
					     &prev_indices,
					     sizeof(u64));

	/* Issue a full memory barrier before updating the write index */
	virt_mb();

	/* Now, update the write location */
	hv_set_next_write_location(outring_info, next_write_location);


	if (lock)
		spin_unlock_irqrestore(&outring_info->ring_lock, flags);

	*signal = hv_need_to_signal(old_write, outring_info);
	return 0;
}

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5.56%
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greg kroah-hartman
29
11.79%
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27.78%
haiyang zhang
haiyang zhang
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10.57%
1
5.56%
bill pemberton
bill pemberton
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1.22%
1
5.56%
nicolas palix
nicolas palix
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0.81%
1
5.56%
vitaly kuznetsov
vitaly kuznetsov
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0.41%
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5.56%
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18
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int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
		       void *buffer, u32 buflen, u32 *buffer_actual_len,
		       u64 *requestid, bool *signal, bool raw)
{
	u32 bytes_avail_toread;
	u32 next_read_location = 0;
	u64 prev_indices = 0;
	struct vmpacket_descriptor desc;
	u32 offset;
	u32 packetlen;
	int ret = 0;

	if (buflen <= 0)
		return -EINVAL;


	*buffer_actual_len = 0;
	*requestid = 0;

	bytes_avail_toread = hv_get_bytes_to_read(inring_info);
	/* Make sure there is something to read */
	if (bytes_avail_toread < sizeof(desc)) {
		/*
                 * No error is set when there is even no header, drivers are
                 * supposed to analyze buffer_actual_len.
                 */
		return ret;
	}

	next_read_location = hv_get_next_read_location(inring_info);
	next_read_location = hv_copyfrom_ringbuffer(inring_info, &desc,
						    sizeof(desc),
						    next_read_location);

	offset = raw ? 0 : (desc.offset8 << 3);
	packetlen = (desc.len8 << 3) - offset;
	*buffer_actual_len = packetlen;
	*requestid = desc.trans_id;

	if (bytes_avail_toread < packetlen + offset)
		return -EAGAIN;

	if (packetlen > buflen)
		return -ENOBUFS;

	next_read_location =
		hv_get_next_readlocation_withoffset(inring_info, offset);

	next_read_location = hv_copyfrom_ringbuffer(inring_info,
						buffer,
						packetlen,
						next_read_location);

	next_read_location = hv_copyfrom_ringbuffer(inring_info,
						&prev_indices,
						sizeof(u64),
						next_read_location);

	/*
         * Make sure all reads are done before we update the read index since
         * the writer may start writing to the read area once the read index
         * is updated.
         */
	virt_mb();

	/* Update the read index */
	hv_set_next_read_location(inring_info, next_read_location);

	*signal = hv_need_to_signal_on_read(inring_info);

	return ret;
}
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hank janssen
58
23.29%
1
5.26%
haiyang zhang
haiyang zhang
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9.24%
1
5.26%
ky srinivasan
ky srinivasan
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8.03%
6
31.58%
greg kroah-hartman
greg kroah-hartman
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4.82%
6
31.58%
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10
4.02%
2
10.53%
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19
100.00%

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368
30.07%
2
4.35%
vitaly kuznetsov
vitaly kuznetsov
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11.52%
3
6.52%
haiyang zhang
haiyang zhang
131
10.70%
2
4.35%
greg kroah-hartman
greg kroah-hartman
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9.89%
11
23.91%
bill pemberton
bill pemberton
21
1.72%
3
6.52%
jason wang
jason wang
3
0.25%
1
2.17%
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nicolas palix
2
0.16%
1
2.17%
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Directory: drivers/hv

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