3 * Copyright (c) 2009, Microsoft Corporation.
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms and conditions of the GNU General Public License,
7 * version 2, as published by the Free Software Foundation.
9 * This program is distributed in the hope it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
14 * You should have received a copy of the GNU General Public License along with
15 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
16 * Place - Suite 330, Boston, MA 02111-1307 USA.
19 * Haiyang Zhang <haiyangz@microsoft.com>
20 * Hank Janssen <hjanssen@microsoft.com>
21 * K. Y. Srinivasan <kys@microsoft.com>
24 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
26 #include <linux/kernel.h>
28 #include <linux/hyperv.h>
29 #include <linux/uio.h>
30 #include <linux/vmalloc.h>
31 #include <linux/slab.h>
33 #include "hyperv_vmbus.h"
35 #define VMBUS_PKT_TRAILER 8
38 * When we write to the ring buffer, check if the host needs to
39 * be signaled. Here is the details of this protocol:
41 * 1. The host guarantees that while it is draining the
42 * ring buffer, it will set the interrupt_mask to
43 * indicate it does not need to be interrupted when
46 * 2. The host guarantees that it will completely drain
47 * the ring buffer before exiting the read loop. Further,
48 * once the ring buffer is empty, it will clear the
49 * interrupt_mask and re-check to see if new data has
53 * It looks like Windows hosts have logic to deal with DOS attacks that
54 * can be triggered if it receives interrupts when it is not expecting
55 * the interrupt. The host expects interrupts only when the ring
56 * transitions from empty to non-empty (or full to non full on the guest
58 * So, base the signaling decision solely on the ring state until the
59 * host logic is fixed.
62 static void hv_signal_on_write(u32 old_write
, struct vmbus_channel
*channel
)
64 struct hv_ring_buffer_info
*rbi
= &channel
->outbound
;
67 if (READ_ONCE(rbi
->ring_buffer
->interrupt_mask
))
70 /* check interrupt_mask before read_index */
73 * This is the only case we need to signal when the
74 * ring transitions from being empty to non-empty.
76 if (old_write
== READ_ONCE(rbi
->ring_buffer
->read_index
))
77 vmbus_setevent(channel
);
82 /* Get the next write location for the specified ring buffer. */
84 hv_get_next_write_location(struct hv_ring_buffer_info
*ring_info
)
86 u32 next
= ring_info
->ring_buffer
->write_index
;
91 /* Set the next write location for the specified ring buffer. */
93 hv_set_next_write_location(struct hv_ring_buffer_info
*ring_info
,
94 u32 next_write_location
)
96 ring_info
->ring_buffer
->write_index
= next_write_location
;
99 /* Get the next read location for the specified ring buffer. */
101 hv_get_next_read_location(const struct hv_ring_buffer_info
*ring_info
)
103 return ring_info
->ring_buffer
->read_index
;
107 * Get the next read location + offset for the specified ring buffer.
108 * This allows the caller to skip.
111 hv_get_next_readlocation_withoffset(const struct hv_ring_buffer_info
*ring_info
,
114 u32 next
= ring_info
->ring_buffer
->read_index
;
117 if (next
>= ring_info
->ring_datasize
)
118 next
-= ring_info
->ring_datasize
;
123 /* Set the next read location for the specified ring buffer. */
125 hv_set_next_read_location(struct hv_ring_buffer_info
*ring_info
,
126 u32 next_read_location
)
128 ring_info
->ring_buffer
->read_index
= next_read_location
;
129 ring_info
->priv_read_index
= next_read_location
;
132 /* Get the size of the ring buffer. */
134 hv_get_ring_buffersize(const struct hv_ring_buffer_info
*ring_info
)
136 return ring_info
->ring_datasize
;
139 /* Get the read and write indices as u64 of the specified ring buffer. */
141 hv_get_ring_bufferindices(struct hv_ring_buffer_info
*ring_info
)
143 return (u64
)ring_info
->ring_buffer
->write_index
<< 32;
147 * Helper routine to copy to source from ring buffer.
148 * Assume there is enough room. Handles wrap-around in src case only!!
150 static u32
hv_copyfrom_ringbuffer(
151 const struct hv_ring_buffer_info
*ring_info
,
154 u32 start_read_offset
)
156 void *ring_buffer
= hv_get_ring_buffer(ring_info
);
157 u32 ring_buffer_size
= hv_get_ring_buffersize(ring_info
);
159 memcpy(dest
, ring_buffer
+ start_read_offset
, destlen
);
161 start_read_offset
+= destlen
;
162 if (start_read_offset
>= ring_buffer_size
)
163 start_read_offset
-= ring_buffer_size
;
165 return start_read_offset
;
170 * Helper routine to copy from source to ring buffer.
171 * Assume there is enough room. Handles wrap-around in dest case only!!
173 static u32
hv_copyto_ringbuffer(
174 struct hv_ring_buffer_info
*ring_info
,
175 u32 start_write_offset
,
179 void *ring_buffer
= hv_get_ring_buffer(ring_info
);
180 u32 ring_buffer_size
= hv_get_ring_buffersize(ring_info
);
182 memcpy(ring_buffer
+ start_write_offset
, src
, srclen
);
184 start_write_offset
+= srclen
;
185 if (start_write_offset
>= ring_buffer_size
)
186 start_write_offset
-= ring_buffer_size
;
188 return start_write_offset
;
191 /* Get various debug metrics for the specified ring buffer. */
192 void hv_ringbuffer_get_debuginfo(const struct hv_ring_buffer_info
*ring_info
,
193 struct hv_ring_buffer_debug_info
*debug_info
)
195 u32 bytes_avail_towrite
;
196 u32 bytes_avail_toread
;
198 if (ring_info
->ring_buffer
) {
199 hv_get_ringbuffer_availbytes(ring_info
,
201 &bytes_avail_towrite
);
203 debug_info
->bytes_avail_toread
= bytes_avail_toread
;
204 debug_info
->bytes_avail_towrite
= bytes_avail_towrite
;
205 debug_info
->current_read_index
=
206 ring_info
->ring_buffer
->read_index
;
207 debug_info
->current_write_index
=
208 ring_info
->ring_buffer
->write_index
;
209 debug_info
->current_interrupt_mask
=
210 ring_info
->ring_buffer
->interrupt_mask
;
214 /* Initialize the ring buffer. */
215 int hv_ringbuffer_init(struct hv_ring_buffer_info
*ring_info
,
216 struct page
*pages
, u32 page_cnt
)
219 struct page
**pages_wraparound
;
221 BUILD_BUG_ON((sizeof(struct hv_ring_buffer
) != PAGE_SIZE
));
223 memset(ring_info
, 0, sizeof(struct hv_ring_buffer_info
));
226 * First page holds struct hv_ring_buffer, do wraparound mapping for
229 pages_wraparound
= kzalloc(sizeof(struct page
*) * (page_cnt
* 2 - 1),
231 if (!pages_wraparound
)
234 pages_wraparound
[0] = pages
;
235 for (i
= 0; i
< 2 * (page_cnt
- 1); i
++)
236 pages_wraparound
[i
+ 1] = &pages
[i
% (page_cnt
- 1) + 1];
238 ring_info
->ring_buffer
= (struct hv_ring_buffer
*)
239 vmap(pages_wraparound
, page_cnt
* 2 - 1, VM_MAP
, PAGE_KERNEL
);
241 kfree(pages_wraparound
);
244 if (!ring_info
->ring_buffer
)
247 ring_info
->ring_buffer
->read_index
=
248 ring_info
->ring_buffer
->write_index
= 0;
250 /* Set the feature bit for enabling flow control. */
251 ring_info
->ring_buffer
->feature_bits
.value
= 1;
253 ring_info
->ring_size
= page_cnt
<< PAGE_SHIFT
;
254 ring_info
->ring_datasize
= ring_info
->ring_size
-
255 sizeof(struct hv_ring_buffer
);
257 spin_lock_init(&ring_info
->ring_lock
);
262 /* Cleanup the ring buffer. */
263 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info
*ring_info
)
265 vunmap(ring_info
->ring_buffer
);
268 /* Write to the ring buffer. */
269 int hv_ringbuffer_write(struct vmbus_channel
*channel
,
270 const struct kvec
*kv_list
, u32 kv_count
)
273 u32 bytes_avail_towrite
;
274 u32 totalbytes_towrite
= 0;
276 u32 next_write_location
;
278 u64 prev_indices
= 0;
279 unsigned long flags
= 0;
280 struct hv_ring_buffer_info
*outring_info
= &channel
->outbound
;
282 if (channel
->rescind
)
285 for (i
= 0; i
< kv_count
; i
++)
286 totalbytes_towrite
+= kv_list
[i
].iov_len
;
288 totalbytes_towrite
+= sizeof(u64
);
290 spin_lock_irqsave(&outring_info
->ring_lock
, flags
);
292 bytes_avail_towrite
= hv_get_bytes_to_write(outring_info
);
295 * If there is only room for the packet, assume it is full.
296 * Otherwise, the next time around, we think the ring buffer
297 * is empty since the read index == write index.
299 if (bytes_avail_towrite
<= totalbytes_towrite
) {
300 spin_unlock_irqrestore(&outring_info
->ring_lock
, flags
);
304 /* Write to the ring buffer */
305 next_write_location
= hv_get_next_write_location(outring_info
);
307 old_write
= next_write_location
;
309 for (i
= 0; i
< kv_count
; i
++) {
310 next_write_location
= hv_copyto_ringbuffer(outring_info
,
316 /* Set previous packet start */
317 prev_indices
= hv_get_ring_bufferindices(outring_info
);
319 next_write_location
= hv_copyto_ringbuffer(outring_info
,
324 /* Issue a full memory barrier before updating the write index */
327 /* Now, update the write location */
328 hv_set_next_write_location(outring_info
, next_write_location
);
331 spin_unlock_irqrestore(&outring_info
->ring_lock
, flags
);
333 hv_signal_on_write(old_write
, channel
);
335 if (channel
->rescind
)
342 init_cached_read_index(struct hv_ring_buffer_info
*rbi
)
344 rbi
->cached_read_index
= rbi
->ring_buffer
->read_index
;
347 int hv_ringbuffer_read(struct vmbus_channel
*channel
,
348 void *buffer
, u32 buflen
, u32
*buffer_actual_len
,
349 u64
*requestid
, bool raw
)
351 u32 bytes_avail_toread
;
352 u32 next_read_location
= 0;
353 u64 prev_indices
= 0;
354 struct vmpacket_descriptor desc
;
358 struct hv_ring_buffer_info
*inring_info
= &channel
->inbound
;
364 *buffer_actual_len
= 0;
367 bytes_avail_toread
= hv_get_bytes_to_read(inring_info
);
368 /* Make sure there is something to read */
369 if (bytes_avail_toread
< sizeof(desc
)) {
371 * No error is set when there is even no header, drivers are
372 * supposed to analyze buffer_actual_len.
377 init_cached_read_index(inring_info
);
379 next_read_location
= hv_get_next_read_location(inring_info
);
380 next_read_location
= hv_copyfrom_ringbuffer(inring_info
, &desc
,
384 offset
= raw
? 0 : (desc
.offset8
<< 3);
385 packetlen
= (desc
.len8
<< 3) - offset
;
386 *buffer_actual_len
= packetlen
;
387 *requestid
= desc
.trans_id
;
389 if (bytes_avail_toread
< packetlen
+ offset
)
392 if (packetlen
> buflen
)
396 hv_get_next_readlocation_withoffset(inring_info
, offset
);
398 next_read_location
= hv_copyfrom_ringbuffer(inring_info
,
403 next_read_location
= hv_copyfrom_ringbuffer(inring_info
,
409 * Make sure all reads are done before we update the read index since
410 * the writer may start writing to the read area once the read index
415 /* Update the read index */
416 hv_set_next_read_location(inring_info
, next_read_location
);
418 hv_signal_on_read(channel
);
424 * Determine number of bytes available in ring buffer after
425 * the current iterator (priv_read_index) location.
427 * This is similar to hv_get_bytes_to_read but with private
428 * read index instead.
430 static u32
hv_pkt_iter_avail(const struct hv_ring_buffer_info
*rbi
)
432 u32 priv_read_loc
= rbi
->priv_read_index
;
433 u32 write_loc
= READ_ONCE(rbi
->ring_buffer
->write_index
);
435 if (write_loc
>= priv_read_loc
)
436 return write_loc
- priv_read_loc
;
438 return (rbi
->ring_datasize
- priv_read_loc
) + write_loc
;
442 * Get first vmbus packet from ring buffer after read_index
444 * If ring buffer is empty, returns NULL and no other action needed.
446 struct vmpacket_descriptor
*hv_pkt_iter_first(struct vmbus_channel
*channel
)
448 struct hv_ring_buffer_info
*rbi
= &channel
->inbound
;
450 /* set state for later hv_signal_on_read() */
451 init_cached_read_index(rbi
);
453 if (hv_pkt_iter_avail(rbi
) < sizeof(struct vmpacket_descriptor
))
456 return hv_get_ring_buffer(rbi
) + rbi
->priv_read_index
;
458 EXPORT_SYMBOL_GPL(hv_pkt_iter_first
);
461 * Get next vmbus packet from ring buffer.
463 * Advances the current location (priv_read_index) and checks for more
464 * data. If the end of the ring buffer is reached, then return NULL.
466 struct vmpacket_descriptor
*
467 __hv_pkt_iter_next(struct vmbus_channel
*channel
,
468 const struct vmpacket_descriptor
*desc
)
470 struct hv_ring_buffer_info
*rbi
= &channel
->inbound
;
471 u32 packetlen
= desc
->len8
<< 3;
472 u32 dsize
= rbi
->ring_datasize
;
474 /* bump offset to next potential packet */
475 rbi
->priv_read_index
+= packetlen
+ VMBUS_PKT_TRAILER
;
476 if (rbi
->priv_read_index
>= dsize
)
477 rbi
->priv_read_index
-= dsize
;
480 if (hv_pkt_iter_avail(rbi
) < sizeof(struct vmpacket_descriptor
))
483 return hv_get_ring_buffer(rbi
) + rbi
->priv_read_index
;
485 EXPORT_SYMBOL_GPL(__hv_pkt_iter_next
);
488 * Update host ring buffer after iterating over packets.
490 void hv_pkt_iter_close(struct vmbus_channel
*channel
)
492 struct hv_ring_buffer_info
*rbi
= &channel
->inbound
;
495 * Make sure all reads are done before we update the read index since
496 * the writer may start writing to the read area once the read index
500 rbi
->ring_buffer
->read_index
= rbi
->priv_read_index
;
502 hv_signal_on_read(channel
);
504 EXPORT_SYMBOL_GPL(hv_pkt_iter_close
);