1 /* 2 * 3 * Copyright (c) 2009, Microsoft Corporation. 4 * 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. 8 * 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 12 * more details. 13 * 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. 17 * 18 * Authors: 19 * Haiyang Zhang <haiyangz@microsoft.com> 20 * Hank Janssen <hjanssen@microsoft.com> 21 * K. Y. Srinivasan <kys@microsoft.com> 22 * 23 */ 24 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 25 26 #include <linux/kernel.h> 27 #include <linux/mm.h> 28 #include <linux/hyperv.h> 29 #include <linux/uio.h> 30 #include <linux/vmalloc.h> 31 #include <linux/slab.h> 32 33 #include "hyperv_vmbus.h" 34 35 void hv_begin_read(struct hv_ring_buffer_info *rbi) 36 { 37 rbi->ring_buffer->interrupt_mask = 1; 38 virt_mb(); 39 } 40 41 u32 hv_end_read(struct hv_ring_buffer_info *rbi) 42 { 43 44 rbi->ring_buffer->interrupt_mask = 0; 45 virt_mb(); 46 47 /* 48 * Now check to see if the ring buffer is still empty. 49 * If it is not, we raced and we need to process new 50 * incoming messages. 51 */ 52 return hv_get_bytes_to_read(rbi); 53 } 54 55 /* 56 * When we write to the ring buffer, check if the host needs to 57 * be signaled. Here is the details of this protocol: 58 * 59 * 1. The host guarantees that while it is draining the 60 * ring buffer, it will set the interrupt_mask to 61 * indicate it does not need to be interrupted when 62 * new data is placed. 63 * 64 * 2. The host guarantees that it will completely drain 65 * the ring buffer before exiting the read loop. Further, 66 * once the ring buffer is empty, it will clear the 67 * interrupt_mask and re-check to see if new data has 68 * arrived. 69 * 70 * KYS: Oct. 30, 2016: 71 * It looks like Windows hosts have logic to deal with DOS attacks that 72 * can be triggered if it receives interrupts when it is not expecting 73 * the interrupt. The host expects interrupts only when the ring 74 * transitions from empty to non-empty (or full to non full on the guest 75 * to host ring). 76 * So, base the signaling decision solely on the ring state until the 77 * host logic is fixed. 78 */ 79 80 static void hv_signal_on_write(u32 old_write, struct vmbus_channel *channel, 81 bool kick_q) 82 { 83 struct hv_ring_buffer_info *rbi = &channel->outbound; 84 85 virt_mb(); 86 if (READ_ONCE(rbi->ring_buffer->interrupt_mask)) 87 return; 88 89 /* check interrupt_mask before read_index */ 90 virt_rmb(); 91 /* 92 * This is the only case we need to signal when the 93 * ring transitions from being empty to non-empty. 94 */ 95 if (old_write == READ_ONCE(rbi->ring_buffer->read_index)) 96 vmbus_setevent(channel); 97 98 return; 99 } 100 101 /* Get the next write location for the specified ring buffer. */ 102 static inline u32 103 hv_get_next_write_location(struct hv_ring_buffer_info *ring_info) 104 { 105 u32 next = ring_info->ring_buffer->write_index; 106 107 return next; 108 } 109 110 /* Set the next write location for the specified ring buffer. */ 111 static inline void 112 hv_set_next_write_location(struct hv_ring_buffer_info *ring_info, 113 u32 next_write_location) 114 { 115 ring_info->ring_buffer->write_index = next_write_location; 116 } 117 118 /* Get the next read location for the specified ring buffer. */ 119 static inline u32 120 hv_get_next_read_location(struct hv_ring_buffer_info *ring_info) 121 { 122 u32 next = ring_info->ring_buffer->read_index; 123 124 return next; 125 } 126 127 /* 128 * Get the next read location + offset for the specified ring buffer. 129 * This allows the caller to skip. 130 */ 131 static inline u32 132 hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info, 133 u32 offset) 134 { 135 u32 next = ring_info->ring_buffer->read_index; 136 137 next += offset; 138 next %= ring_info->ring_datasize; 139 140 return next; 141 } 142 143 /* Set the next read location for the specified ring buffer. */ 144 static inline void 145 hv_set_next_read_location(struct hv_ring_buffer_info *ring_info, 146 u32 next_read_location) 147 { 148 ring_info->ring_buffer->read_index = next_read_location; 149 ring_info->priv_read_index = next_read_location; 150 } 151 152 /* Get the size of the ring buffer. */ 153 static inline u32 154 hv_get_ring_buffersize(struct hv_ring_buffer_info *ring_info) 155 { 156 return ring_info->ring_datasize; 157 } 158 159 /* Get the read and write indices as u64 of the specified ring buffer. */ 160 static inline u64 161 hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info) 162 { 163 return (u64)ring_info->ring_buffer->write_index << 32; 164 } 165 166 /* 167 * Helper routine to copy to source from ring buffer. 168 * Assume there is enough room. Handles wrap-around in src case only!! 169 */ 170 static u32 hv_copyfrom_ringbuffer( 171 struct hv_ring_buffer_info *ring_info, 172 void *dest, 173 u32 destlen, 174 u32 start_read_offset) 175 { 176 void *ring_buffer = hv_get_ring_buffer(ring_info); 177 u32 ring_buffer_size = hv_get_ring_buffersize(ring_info); 178 179 memcpy(dest, ring_buffer + start_read_offset, destlen); 180 181 start_read_offset += destlen; 182 start_read_offset %= ring_buffer_size; 183 184 return start_read_offset; 185 } 186 187 188 /* 189 * Helper routine to copy from source to ring buffer. 190 * Assume there is enough room. Handles wrap-around in dest case only!! 191 */ 192 static u32 hv_copyto_ringbuffer( 193 struct hv_ring_buffer_info *ring_info, 194 u32 start_write_offset, 195 void *src, 196 u32 srclen) 197 { 198 void *ring_buffer = hv_get_ring_buffer(ring_info); 199 u32 ring_buffer_size = hv_get_ring_buffersize(ring_info); 200 201 memcpy(ring_buffer + start_write_offset, src, srclen); 202 203 start_write_offset += srclen; 204 start_write_offset %= ring_buffer_size; 205 206 return start_write_offset; 207 } 208 209 /* Get various debug metrics for the specified ring buffer. */ 210 void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info, 211 struct hv_ring_buffer_debug_info *debug_info) 212 { 213 u32 bytes_avail_towrite; 214 u32 bytes_avail_toread; 215 216 if (ring_info->ring_buffer) { 217 hv_get_ringbuffer_availbytes(ring_info, 218 &bytes_avail_toread, 219 &bytes_avail_towrite); 220 221 debug_info->bytes_avail_toread = bytes_avail_toread; 222 debug_info->bytes_avail_towrite = bytes_avail_towrite; 223 debug_info->current_read_index = 224 ring_info->ring_buffer->read_index; 225 debug_info->current_write_index = 226 ring_info->ring_buffer->write_index; 227 debug_info->current_interrupt_mask = 228 ring_info->ring_buffer->interrupt_mask; 229 } 230 } 231 232 /* Initialize the ring buffer. */ 233 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info, 234 struct page *pages, u32 page_cnt) 235 { 236 int i; 237 struct page **pages_wraparound; 238 239 BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE)); 240 241 memset(ring_info, 0, sizeof(struct hv_ring_buffer_info)); 242 243 /* 244 * First page holds struct hv_ring_buffer, do wraparound mapping for 245 * the rest. 246 */ 247 pages_wraparound = kzalloc(sizeof(struct page *) * (page_cnt * 2 - 1), 248 GFP_KERNEL); 249 if (!pages_wraparound) 250 return -ENOMEM; 251 252 pages_wraparound[0] = pages; 253 for (i = 0; i < 2 * (page_cnt - 1); i++) 254 pages_wraparound[i + 1] = &pages[i % (page_cnt - 1) + 1]; 255 256 ring_info->ring_buffer = (struct hv_ring_buffer *) 257 vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP, PAGE_KERNEL); 258 259 kfree(pages_wraparound); 260 261 262 if (!ring_info->ring_buffer) 263 return -ENOMEM; 264 265 ring_info->ring_buffer->read_index = 266 ring_info->ring_buffer->write_index = 0; 267 268 /* Set the feature bit for enabling flow control. */ 269 ring_info->ring_buffer->feature_bits.value = 1; 270 271 ring_info->ring_size = page_cnt << PAGE_SHIFT; 272 ring_info->ring_datasize = ring_info->ring_size - 273 sizeof(struct hv_ring_buffer); 274 275 spin_lock_init(&ring_info->ring_lock); 276 277 return 0; 278 } 279 280 /* Cleanup the ring buffer. */ 281 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info) 282 { 283 vunmap(ring_info->ring_buffer); 284 } 285 286 /* Write to the ring buffer. */ 287 int hv_ringbuffer_write(struct vmbus_channel *channel, 288 struct kvec *kv_list, u32 kv_count, bool lock, 289 bool kick_q) 290 { 291 int i = 0; 292 u32 bytes_avail_towrite; 293 u32 totalbytes_towrite = 0; 294 295 u32 next_write_location; 296 u32 old_write; 297 u64 prev_indices = 0; 298 unsigned long flags = 0; 299 struct hv_ring_buffer_info *outring_info = &channel->outbound; 300 301 for (i = 0; i < kv_count; i++) 302 totalbytes_towrite += kv_list[i].iov_len; 303 304 totalbytes_towrite += sizeof(u64); 305 306 if (lock) 307 spin_lock_irqsave(&outring_info->ring_lock, flags); 308 309 bytes_avail_towrite = hv_get_bytes_to_write(outring_info); 310 311 /* 312 * If there is only room for the packet, assume it is full. 313 * Otherwise, the next time around, we think the ring buffer 314 * is empty since the read index == write index. 315 */ 316 if (bytes_avail_towrite <= totalbytes_towrite) { 317 if (lock) 318 spin_unlock_irqrestore(&outring_info->ring_lock, flags); 319 return -EAGAIN; 320 } 321 322 /* Write to the ring buffer */ 323 next_write_location = hv_get_next_write_location(outring_info); 324 325 old_write = next_write_location; 326 327 for (i = 0; i < kv_count; i++) { 328 next_write_location = hv_copyto_ringbuffer(outring_info, 329 next_write_location, 330 kv_list[i].iov_base, 331 kv_list[i].iov_len); 332 } 333 334 /* Set previous packet start */ 335 prev_indices = hv_get_ring_bufferindices(outring_info); 336 337 next_write_location = hv_copyto_ringbuffer(outring_info, 338 next_write_location, 339 &prev_indices, 340 sizeof(u64)); 341 342 /* Issue a full memory barrier before updating the write index */ 343 virt_mb(); 344 345 /* Now, update the write location */ 346 hv_set_next_write_location(outring_info, next_write_location); 347 348 349 if (lock) 350 spin_unlock_irqrestore(&outring_info->ring_lock, flags); 351 352 hv_signal_on_write(old_write, channel, kick_q); 353 return 0; 354 } 355 356 int hv_ringbuffer_read(struct vmbus_channel *channel, 357 void *buffer, u32 buflen, u32 *buffer_actual_len, 358 u64 *requestid, bool raw) 359 { 360 u32 bytes_avail_toread; 361 u32 next_read_location = 0; 362 u64 prev_indices = 0; 363 struct vmpacket_descriptor desc; 364 u32 offset; 365 u32 packetlen; 366 int ret = 0; 367 struct hv_ring_buffer_info *inring_info = &channel->inbound; 368 369 if (buflen <= 0) 370 return -EINVAL; 371 372 373 *buffer_actual_len = 0; 374 *requestid = 0; 375 376 bytes_avail_toread = hv_get_bytes_to_read(inring_info); 377 /* Make sure there is something to read */ 378 if (bytes_avail_toread < sizeof(desc)) { 379 /* 380 * No error is set when there is even no header, drivers are 381 * supposed to analyze buffer_actual_len. 382 */ 383 return ret; 384 } 385 386 next_read_location = hv_get_next_read_location(inring_info); 387 next_read_location = hv_copyfrom_ringbuffer(inring_info, &desc, 388 sizeof(desc), 389 next_read_location); 390 391 offset = raw ? 0 : (desc.offset8 << 3); 392 packetlen = (desc.len8 << 3) - offset; 393 *buffer_actual_len = packetlen; 394 *requestid = desc.trans_id; 395 396 if (bytes_avail_toread < packetlen + offset) 397 return -EAGAIN; 398 399 if (packetlen > buflen) 400 return -ENOBUFS; 401 402 next_read_location = 403 hv_get_next_readlocation_withoffset(inring_info, offset); 404 405 next_read_location = hv_copyfrom_ringbuffer(inring_info, 406 buffer, 407 packetlen, 408 next_read_location); 409 410 next_read_location = hv_copyfrom_ringbuffer(inring_info, 411 &prev_indices, 412 sizeof(u64), 413 next_read_location); 414 415 /* 416 * Make sure all reads are done before we update the read index since 417 * the writer may start writing to the read area once the read index 418 * is updated. 419 */ 420 virt_mb(); 421 422 /* Update the read index */ 423 hv_set_next_read_location(inring_info, next_read_location); 424 425 hv_signal_on_read(channel); 426 427 return ret; 428 } 429