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2024-12-19 9370bb92b2d16684ee45cf24e879c93c509162da 
 kernel/drivers/hv/ring_buffer.c
....@@ -1,25 +1,12 @@
1
+// SPDX-License-Identifier: GPL-2.0-only
12 /*
23  *
34  * Copyright (c) 2009, Microsoft Corporation.
4
- *
5
- * This program is free software; you can redistribute it and/or modify it
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- * under the terms and conditions of the GNU General Public License,
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- * version 2, as published by the Free Software Foundation.
8
- *
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- * This program is distributed in the hope it will be useful, but WITHOUT
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- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
12
- * more details.
13
- *
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- * You should have received a copy of the GNU General Public License along with
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- * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
16
- * Place - Suite 330, Boston, MA 02111-1307 USA.
175  *
186  * Authors:
197  *   Haiyang Zhang <haiyangz@microsoft.com>
208  *   Hank Janssen  <hjanssen@microsoft.com>
219  *   K. Y. Srinivasan <kys@microsoft.com>
22
- *
2310  */
2411 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
2512 
....@@ -74,8 +61,10 @@
7461 	 * This is the only case we need to signal when the
7562 	 * ring transitions from being empty to non-empty.
7663 	 */
77
-	if (old_write == READ_ONCE(rbi->ring_buffer->read_index))
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+	if (old_write == READ_ONCE(rbi->ring_buffer->read_index)) {
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+		++channel->intr_out_empty;
7866 		vmbus_setevent(channel);
67
+	}
7968 }
8069 
8170 /* Get the next write location for the specified ring buffer. */
....@@ -164,14 +153,18 @@
164153 }
165154 
166155 /* Get various debug metrics for the specified ring buffer. */
167
-int hv_ringbuffer_get_debuginfo(const struct hv_ring_buffer_info *ring_info,
156
+int hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
168157 				struct hv_ring_buffer_debug_info *debug_info)
169158 {
170159 	u32 bytes_avail_towrite;
171160 	u32 bytes_avail_toread;
172161 
173
-	if (!ring_info->ring_buffer)
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+	mutex_lock(&ring_info->ring_buffer_mutex);
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+
164
+	if (!ring_info->ring_buffer) {
165
+		mutex_unlock(&ring_info->ring_buffer_mutex);
174166 		return -EINVAL;
167
+	}
175168 
176169 	hv_get_ringbuffer_availbytes(ring_info,
177170 				     &bytes_avail_toread,
....@@ -182,9 +175,18 @@
182175 	debug_info->current_write_index = ring_info->ring_buffer->write_index;
183176 	debug_info->current_interrupt_mask
184177 		= ring_info->ring_buffer->interrupt_mask;
178
+	mutex_unlock(&ring_info->ring_buffer_mutex);
179
+
185180 	return 0;
186181 }
187182 EXPORT_SYMBOL_GPL(hv_ringbuffer_get_debuginfo);
183
+
184
+/* Initialize a channel's ring buffer info mutex locks */
185
+void hv_ringbuffer_pre_init(struct vmbus_channel *channel)
186
+{
187
+	mutex_init(&channel->inbound.ring_buffer_mutex);
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+	mutex_init(&channel->outbound.ring_buffer_mutex);
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+}
188190 
189191 /* Initialize the ring buffer. */
190192 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
....@@ -194,8 +196,6 @@
194196 	struct page **pages_wraparound;
195197 
196198 	BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE));
197
-
198
-	memset(ring_info, 0, sizeof(struct hv_ring_buffer_info));
199199 
200200 	/*
201201 	 * First page holds struct hv_ring_buffer, do wraparound mapping for
....@@ -230,6 +230,7 @@
230230 		reciprocal_value(ring_info->ring_size / 10);
231231 	ring_info->ring_datasize = ring_info->ring_size -
232232 		sizeof(struct hv_ring_buffer);
233
+	ring_info->priv_read_index = 0;
233234 
234235 	spin_lock_init(&ring_info->ring_lock);
235236 
....@@ -239,8 +240,24 @@
239240 /* Cleanup the ring buffer. */
240241 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
241242 {
243
+	mutex_lock(&ring_info->ring_buffer_mutex);
242244 	vunmap(ring_info->ring_buffer);
245
+	ring_info->ring_buffer = NULL;
246
+	mutex_unlock(&ring_info->ring_buffer_mutex);
243247 }
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+
249
+/*
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+ * Check if the ring buffer spinlock is available to take or not; used on
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+ * atomic contexts, like panic path (see the Hyper-V framebuffer driver).
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+ */
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+
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+bool hv_ringbuffer_spinlock_busy(struct vmbus_channel *channel)
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+{
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+	struct hv_ring_buffer_info *rinfo = &channel->outbound;
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+
258
+	return spin_is_locked(&rinfo->ring_lock);
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+}
260
+EXPORT_SYMBOL_GPL(hv_ringbuffer_spinlock_busy);
244261 
245262 /* Write to the ring buffer. */
246263 int hv_ringbuffer_write(struct vmbus_channel *channel,
....@@ -271,9 +288,18 @@
271288 	 * is empty since the read index == write index.
272289 	 */
273290 	if (bytes_avail_towrite <= totalbytes_towrite) {
291
+		++channel->out_full_total;
292
+
293
+		if (!channel->out_full_flag) {
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+			++channel->out_full_first;
295
+			channel->out_full_flag = true;
296
+		}
297
+
274298 		spin_unlock_irqrestore(&outring_info->ring_lock, flags);
275299 		return -EAGAIN;
276300 	}
301
+
302
+	channel->out_full_flag = false;
277303 
278304 	/* Write to the ring buffer */
279305 	next_write_location = hv_get_next_write_location(outring_info);
....@@ -365,7 +391,16 @@
365391 static u32 hv_pkt_iter_avail(const struct hv_ring_buffer_info *rbi)
366392 {
367393 	u32 priv_read_loc = rbi->priv_read_index;
368
-	u32 write_loc = READ_ONCE(rbi->ring_buffer->write_index);
394
+	u32 write_loc;
395
+
396
+	/*
397
+	 * The Hyper-V host writes the packet data, then uses
398
+	 * store_release() to update the write_index.  Use load_acquire()
399
+	 * here to prevent loads of the packet data from being re-ordered
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+	 * before the read of the write_index and potentially getting
401
+	 * stale data.
402
+	 */
403
+	write_loc = virt_load_acquire(&rbi->ring_buffer->write_index);
369404 
370405 	if (write_loc >= priv_read_loc)
371406 		return write_loc - priv_read_loc;
....@@ -383,6 +418,7 @@
383418 	struct hv_ring_buffer_info *rbi = &channel->inbound;
384419 	struct vmpacket_descriptor *desc;
385420 
421
+	hv_debug_delay_test(channel, MESSAGE_DELAY);
386422 	if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
387423 		return NULL;
388424 
....@@ -408,6 +444,7 @@
408444 	u32 packetlen = desc->len8 << 3;
409445 	u32 dsize = rbi->ring_datasize;
410446 
447
+	hv_debug_delay_test(channel, MESSAGE_DELAY);
411448 	/* bump offset to next potential packet */
412449 	rbi->priv_read_index += packetlen + VMBUS_PKT_TRAILER;
413450 	if (rbi->priv_read_index >= dsize)
....@@ -529,6 +566,7 @@
529566 	if (curr_write_sz <= pending_sz)
530567 		return;
531568 
569
+	++channel->intr_in_full;
532570 	vmbus_setevent(channel);
533571 }
534572 EXPORT_SYMBOL_GPL(hv_pkt_iter_close);