Release 4.11 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 <linux/vmalloc.h>
#include <linux/slab.h>

#include "hyperv_vmbus.h"

/*
 * 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.
 *
 * KYS: Oct. 30, 2016:
 * It looks like Windows hosts have logic to deal with DOS attacks that
 * can be triggered if it receives interrupts when it is not expecting
 * the interrupt. The host expects interrupts only when the ring
 * transitions from empty to non-empty (or full to non full on the guest
 * to host ring).
 * So, base the signaling decision solely on the ring state until the
 * host logic is fixed.
 */



static void hv_signal_on_write(u32 old_write, struct vmbus_channel *channel)
{
	struct hv_ring_buffer_info *rbi = &channel->outbound;

	virt_mb();
	if (READ_ONCE(rbi->ring_buffer->interrupt_mask))
		return;

	/* 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))
		vmbus_setevent(channel);

	return;
}

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K. Y. Srinivasan
60
95.24%
5
83.33%
Jason (Hui) Wang
3
4.76%
1
16.67%
Total
63
100.00%
6
100.00%

/* 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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Hank Janssen
15
62.50%
1
16.67%
Haiyang Zhang
4
16.67%
2
33.33%
Greg Kroah-Hartman
4
16.67%
2
33.33%
K. Y. Srinivasan
1
4.17%
1
16.67%
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24
100.00%
6
100.00%

/* 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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CommitProp
Hank Janssen
13
56.52%
1
16.67%
Haiyang Zhang
6
26.09%
2
33.33%
Greg Kroah-Hartman
3
13.04%
2
33.33%
K. Y. Srinivasan
1
4.35%
1
16.67%
Total
23
100.00%
6
100.00%

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

static inline u32

hv_get_next_read_location(const struct hv_ring_buffer_info *ring_info)
{
	return ring_info->ring_buffer->read_index;
}

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Hank Janssen
10
50.00%
1
14.29%
Haiyang Zhang
4
20.00%
2
28.57%
Greg Kroah-Hartman
3
15.00%
2
28.57%
Stephen Hemminger
2
10.00%
1
14.29%
K. Y. Srinivasan
1
5.00%
1
14.29%
Total
20
100.00%
7
100.00%

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

	next += offset;
	if (next >= ring_info->ring_datasize)
		next -= ring_info->ring_datasize;

	return next;
}

Contributors
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CommitProp
Hank Janssen
22
47.83%
1
12.50%
Stephen Hemminger
10
21.74%
2
25.00%
Haiyang Zhang
8
17.39%
2
25.00%
Greg Kroah-Hartman
5
10.87%
2
25.00%
K. Y. Srinivasan
1
2.17%
1
12.50%
Total
46
100.00%
8
100.00%

/* 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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Hank Janssen
13
44.83%
1
14.29%
K. Y. Srinivasan
7
24.14%
2
28.57%
Haiyang Zhang
6
20.69%
2
28.57%
Greg Kroah-Hartman
3
10.34%
2
28.57%
Total
29
100.00%
7
100.00%

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

static inline u32

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

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Hank Janssen
10
55.56%
1
14.29%
Haiyang Zhang
3
16.67%
2
28.57%
Greg Kroah-Hartman
3
16.67%
2
28.57%
K. Y. Srinivasan
1
5.56%
1
14.29%
Stephen Hemminger
1
5.56%
1
14.29%
Total
18
100.00%
7
100.00%

/* 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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Hank Janssen
15
62.50%
1
16.67%
Haiyang Zhang
4
16.67%
2
33.33%
Greg Kroah-Hartman
4
16.67%
2
33.33%
K. Y. Srinivasan
1
4.17%
1
16.67%
Total
24
100.00%
6
100.00%

/*
 * 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(
	const 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);

	memcpy(dest, ring_buffer + start_read_offset, destlen);

	start_read_offset += destlen;
	if (start_read_offset >= ring_buffer_size)
		start_read_offset -= ring_buffer_size;

	return start_read_offset;
}


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K. Y. Srinivasan
46
68.66%
1
12.50%
Stephen Hemminger
8
11.94%
2
25.00%
Hank Janssen
6
8.96%
1
12.50%
Greg Kroah-Hartman
6
8.96%
3
37.50%
Haiyang Zhang
1
1.49%
1
12.50%
Total
67
100.00%
8
100.00%

/*
 * 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,
	const void			*src,
	u32				srclen)
{
	void *ring_buffer = hv_get_ring_buffer(ring_info);
	u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);

	memcpy(ring_buffer + start_write_offset, src, srclen);

	start_write_offset += srclen;
	if (start_write_offset >= ring_buffer_size)
		start_write_offset -= ring_buffer_size;

	return start_write_offset;
}

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K. Y. Srinivasan
46
68.66%
2
22.22%
Stephen Hemminger
8
11.94%
2
22.22%
Greg Kroah-Hartman
6
8.96%
3
33.33%
Hank Janssen
6
8.96%
1
11.11%
Haiyang Zhang
1
1.49%
1
11.11%
Total
67
100.00%
9
100.00%

/* Get various debug metrics for the specified ring buffer. */


void hv_ringbuffer_get_debuginfo(const 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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Hank Janssen
43
51.81%
1
10.00%
Haiyang Zhang
24
28.92%
2
20.00%
Greg Kroah-Hartman
13
15.66%
4
40.00%
K. Y. Srinivasan
2
2.41%
2
20.00%
Stephen Hemminger
1
1.20%
1
10.00%
Total
83
100.00%
10
100.00%

/* Initialize the ring buffer. */


int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
		       struct page *pages, u32 page_cnt)
{
	int i;
	struct page **pages_wraparound;

	BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE));

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

	/*
         * First page holds struct hv_ring_buffer, do wraparound mapping for
         * the rest.
         */
	pages_wraparound = kzalloc(sizeof(struct page *) * (page_cnt * 2 - 1),
				   GFP_KERNEL);
	if (!pages_wraparound)
		return -ENOMEM;

	pages_wraparound[0] = pages;
	for (i = 0; i < 2 * (page_cnt - 1); i++)
		pages_wraparound[i + 1] = &pages[i % (page_cnt - 1) + 1];

	ring_info->ring_buffer = (struct hv_ring_buffer *)
		vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP, PAGE_KERNEL);

	kfree(pages_wraparound);


	if (!ring_info->ring_buffer)
		return -ENOMEM;

	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 = page_cnt << PAGE_SHIFT;
	ring_info->ring_datasize = ring_info->ring_size -
		sizeof(struct hv_ring_buffer);

	spin_lock_init(&ring_info->ring_lock);

	return 0;
}

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Vitaly Kuznetsov
135
58.70%
2
15.38%
Hank Janssen
51
22.17%
1
7.69%
Greg Kroah-Hartman
17
7.39%
5
38.46%
Haiyang Zhang
15
6.52%
2
15.38%
K. Y. Srinivasan
11
4.78%
2
15.38%
Bill Pemberton
1
0.43%
1
7.69%
Total
230
100.00%
13
100.00%

/* Cleanup the ring buffer. */


void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
{
	vunmap(ring_info->ring_buffer);
}

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Vitaly Kuznetsov
9
52.94%
1
16.67%
Hank Janssen
3
17.65%
1
16.67%
Greg Kroah-Hartman
3
17.65%
2
33.33%
K. Y. Srinivasan
1
5.88%
1
16.67%
Haiyang Zhang
1
5.88%
1
16.67%
Total
17
100.00%
6
100.00%

/* Write to the ring buffer. */


int hv_ringbuffer_write(struct vmbus_channel *channel,
			const struct kvec *kv_list, u32 kv_count)
{
	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;
	struct hv_ring_buffer_info *outring_info = &channel->outbound;

	if (channel->rescind)
		return -ENODEV;

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

	totalbytes_towrite += sizeof(u64);

	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) {
		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);


	spin_unlock_irqrestore(&outring_info->ring_lock, flags);

	hv_signal_on_write(old_write, channel);

	if (channel->rescind)
		return -ENODEV;

	return 0;
}

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K. Y. Srinivasan
107
41.96%
10
47.62%
Hank Janssen
88
34.51%
1
4.76%
Greg Kroah-Hartman
28
10.98%
5
23.81%
Haiyang Zhang
25
9.80%
1
4.76%
Bill Pemberton
3
1.18%
1
4.76%
Nicolas Palix
2
0.78%
1
4.76%
Vitaly Kuznetsov
1
0.39%
1
4.76%
Stephen Hemminger
1
0.39%
1
4.76%
Total
255
100.00%
21
100.00%



int hv_ringbuffer_read(struct vmbus_channel *channel,
		       void *buffer, u32 buflen, u32 *buffer_actual_len,
		       u64 *requestid, 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;
	struct hv_ring_buffer_info *inring_info = &channel->inbound;

	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;
	}

	init_cached_read_index(channel);
	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);

	hv_signal_on_read(channel);

	return ret;
}
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Vitaly Kuznetsov
119
46.30%
3
14.29%
Hank Janssen
58
22.57%
1
4.76%
K. Y. Srinivasan
32
12.45%
7
33.33%
Haiyang Zhang
22
8.56%
1
4.76%
Greg Kroah-Hartman
11
4.28%
6
28.57%
Bill Pemberton
10
3.89%
2
9.52%
Dexuan Cui
5
1.95%
1
4.76%
Total
257
100.00%
21
100.00%

Overall Contributors
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Tokens
Prop
Commits
CommitProp
Hank Janssen
362
28.59%
2
3.92%
K. Y. Srinivasan
326
25.75%
25
49.02%
Vitaly Kuznetsov
283
22.35%
4
7.84%
Haiyang Zhang
124
9.79%
2
3.92%
Greg Kroah-Hartman
116
9.16%
10
19.61%
Stephen Hemminger
31
2.45%
2
3.92%
Bill Pemberton
14
1.11%
3
5.88%
Dexuan Cui
5
0.39%
1
1.96%
Jason (Hui) Wang
3
0.24%
1
1.96%
Nicolas Palix
2
0.16%
1
1.96%
Total
1266
100.00%
51
100.00%
Directory: drivers/hv

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