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1// SPDX-License-Identifier: GPL-2.0-only2/*3 *4 * Copyright (c) 2009, Microsoft Corporation.5 *6 * Authors:7 * Haiyang Zhang <haiyangz@microsoft.com>8 * Hank Janssen <hjanssen@microsoft.com>9 * K. Y. Srinivasan <kys@microsoft.com>10 */11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt12 13#include <linux/kernel.h>14#include <linux/mm.h>15#include <linux/hyperv.h>16#include <linux/uio.h>17#include <linux/vmalloc.h>18#include <linux/slab.h>19#include <linux/prefetch.h>20#include <linux/io.h>21#include <asm/mshyperv.h>22 23#include "hyperv_vmbus.h"24 25#define VMBUS_PKT_TRAILER 826 27/*28 * When we write to the ring buffer, check if the host needs to29 * be signaled. Here is the details of this protocol:30 *31 * 1. The host guarantees that while it is draining the32 * ring buffer, it will set the interrupt_mask to33 * indicate it does not need to be interrupted when34 * new data is placed.35 *36 * 2. The host guarantees that it will completely drain37 * the ring buffer before exiting the read loop. Further,38 * once the ring buffer is empty, it will clear the39 * interrupt_mask and re-check to see if new data has40 * arrived.41 *42 * KYS: Oct. 30, 2016:43 * It looks like Windows hosts have logic to deal with DOS attacks that44 * can be triggered if it receives interrupts when it is not expecting45 * the interrupt. The host expects interrupts only when the ring46 * transitions from empty to non-empty (or full to non full on the guest47 * to host ring).48 * So, base the signaling decision solely on the ring state until the49 * host logic is fixed.50 */51 52static void hv_signal_on_write(u32 old_write, struct vmbus_channel *channel)53{54 struct hv_ring_buffer_info *rbi = &channel->outbound;55 56 virt_mb();57 if (READ_ONCE(rbi->ring_buffer->interrupt_mask))58 return;59 60 /* check interrupt_mask before read_index */61 virt_rmb();62 /*63 * This is the only case we need to signal when the64 * ring transitions from being empty to non-empty.65 */66 if (old_write == READ_ONCE(rbi->ring_buffer->read_index)) {67 ++channel->intr_out_empty;68 vmbus_setevent(channel);69 }70}71 72/* Get the next write location for the specified ring buffer. */73static inline u3274hv_get_next_write_location(struct hv_ring_buffer_info *ring_info)75{76 u32 next = ring_info->ring_buffer->write_index;77 78 return next;79}80 81/* Set the next write location for the specified ring buffer. */82static inline void83hv_set_next_write_location(struct hv_ring_buffer_info *ring_info,84 u32 next_write_location)85{86 ring_info->ring_buffer->write_index = next_write_location;87}88 89/* Get the size of the ring buffer. */90static inline u3291hv_get_ring_buffersize(const struct hv_ring_buffer_info *ring_info)92{93 return ring_info->ring_datasize;94}95 96/* Get the read and write indices as u64 of the specified ring buffer. */97static inline u6498hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info)99{100 return (u64)ring_info->ring_buffer->write_index << 32;101}102 103/*104 * Helper routine to copy from source to ring buffer.105 * Assume there is enough room. Handles wrap-around in dest case only!!106 */107static u32 hv_copyto_ringbuffer(108 struct hv_ring_buffer_info *ring_info,109 u32 start_write_offset,110 const void *src,111 u32 srclen)112{113 void *ring_buffer = hv_get_ring_buffer(ring_info);114 u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);115 116 memcpy(ring_buffer + start_write_offset, src, srclen);117 118 start_write_offset += srclen;119 if (start_write_offset >= ring_buffer_size)120 start_write_offset -= ring_buffer_size;121 122 return start_write_offset;123}124 125/*126 *127 * hv_get_ringbuffer_availbytes()128 *129 * Get number of bytes available to read and to write to130 * for the specified ring buffer131 */132static void133hv_get_ringbuffer_availbytes(const struct hv_ring_buffer_info *rbi,134 u32 *read, u32 *write)135{136 u32 read_loc, write_loc, dsize;137 138 /* Capture the read/write indices before they changed */139 read_loc = READ_ONCE(rbi->ring_buffer->read_index);140 write_loc = READ_ONCE(rbi->ring_buffer->write_index);141 dsize = rbi->ring_datasize;142 143 *write = write_loc >= read_loc ? dsize - (write_loc - read_loc) :144 read_loc - write_loc;145 *read = dsize - *write;146}147 148/* Get various debug metrics for the specified ring buffer. */149int hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,150 struct hv_ring_buffer_debug_info *debug_info)151{152 u32 bytes_avail_towrite;153 u32 bytes_avail_toread;154 155 mutex_lock(&ring_info->ring_buffer_mutex);156 157 if (!ring_info->ring_buffer) {158 mutex_unlock(&ring_info->ring_buffer_mutex);159 return -EINVAL;160 }161 162 hv_get_ringbuffer_availbytes(ring_info,163 &bytes_avail_toread,164 &bytes_avail_towrite);165 debug_info->bytes_avail_toread = bytes_avail_toread;166 debug_info->bytes_avail_towrite = bytes_avail_towrite;167 debug_info->current_read_index = ring_info->ring_buffer->read_index;168 debug_info->current_write_index = ring_info->ring_buffer->write_index;169 debug_info->current_interrupt_mask170 = ring_info->ring_buffer->interrupt_mask;171 mutex_unlock(&ring_info->ring_buffer_mutex);172 173 return 0;174}175EXPORT_SYMBOL_GPL(hv_ringbuffer_get_debuginfo);176 177/* Initialize a channel's ring buffer info mutex locks */178void hv_ringbuffer_pre_init(struct vmbus_channel *channel)179{180 mutex_init(&channel->inbound.ring_buffer_mutex);181 mutex_init(&channel->outbound.ring_buffer_mutex);182}183 184/* Initialize the ring buffer. */185int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,186 struct page *pages, u32 page_cnt, u32 max_pkt_size)187{188 struct page **pages_wraparound;189 int i;190 191 BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE));192 193 /*194 * First page holds struct hv_ring_buffer, do wraparound mapping for195 * the rest.196 */197 pages_wraparound = kcalloc(page_cnt * 2 - 1,198 sizeof(struct page *),199 GFP_KERNEL);200 if (!pages_wraparound)201 return -ENOMEM;202 203 pages_wraparound[0] = pages;204 for (i = 0; i < 2 * (page_cnt - 1); i++)205 pages_wraparound[i + 1] =206 &pages[i % (page_cnt - 1) + 1];207 208 ring_info->ring_buffer = (struct hv_ring_buffer *)209 vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP,210 pgprot_decrypted(PAGE_KERNEL));211 212 kfree(pages_wraparound);213 if (!ring_info->ring_buffer)214 return -ENOMEM;215 216 /*217 * Ensure the header page is zero'ed since218 * encryption status may have changed.219 */220 memset(ring_info->ring_buffer, 0, HV_HYP_PAGE_SIZE);221 222 ring_info->ring_buffer->read_index =223 ring_info->ring_buffer->write_index = 0;224 225 /* Set the feature bit for enabling flow control. */226 ring_info->ring_buffer->feature_bits.value = 1;227 228 ring_info->ring_size = page_cnt << PAGE_SHIFT;229 ring_info->ring_size_div10_reciprocal =230 reciprocal_value(ring_info->ring_size / 10);231 ring_info->ring_datasize = ring_info->ring_size -232 sizeof(struct hv_ring_buffer);233 ring_info->priv_read_index = 0;234 235 /* Initialize buffer that holds copies of incoming packets */236 if (max_pkt_size) {237 ring_info->pkt_buffer = kzalloc(max_pkt_size, GFP_KERNEL);238 if (!ring_info->pkt_buffer)239 return -ENOMEM;240 ring_info->pkt_buffer_size = max_pkt_size;241 }242 243 spin_lock_init(&ring_info->ring_lock);244 245 return 0;246}247 248/* Cleanup the ring buffer. */249void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)250{251 mutex_lock(&ring_info->ring_buffer_mutex);252 vunmap(ring_info->ring_buffer);253 ring_info->ring_buffer = NULL;254 mutex_unlock(&ring_info->ring_buffer_mutex);255 256 kfree(ring_info->pkt_buffer);257 ring_info->pkt_buffer = NULL;258 ring_info->pkt_buffer_size = 0;259}260 261/*262 * Check if the ring buffer spinlock is available to take or not; used on263 * atomic contexts, like panic path (see the Hyper-V framebuffer driver).264 */265 266bool hv_ringbuffer_spinlock_busy(struct vmbus_channel *channel)267{268 struct hv_ring_buffer_info *rinfo = &channel->outbound;269 270 return spin_is_locked(&rinfo->ring_lock);271}272EXPORT_SYMBOL_GPL(hv_ringbuffer_spinlock_busy);273 274/* Write to the ring buffer. */275int hv_ringbuffer_write(struct vmbus_channel *channel,276 const struct kvec *kv_list, u32 kv_count,277 u64 requestid, u64 *trans_id)278{279 int i;280 u32 bytes_avail_towrite;281 u32 totalbytes_towrite = sizeof(u64);282 u32 next_write_location;283 u32 old_write;284 u64 prev_indices;285 unsigned long flags;286 struct hv_ring_buffer_info *outring_info = &channel->outbound;287 struct vmpacket_descriptor *desc = kv_list[0].iov_base;288 u64 __trans_id, rqst_id = VMBUS_NO_RQSTOR;289 290 if (channel->rescind)291 return -ENODEV;292 293 for (i = 0; i < kv_count; i++)294 totalbytes_towrite += kv_list[i].iov_len;295 296 spin_lock_irqsave(&outring_info->ring_lock, flags);297 298 bytes_avail_towrite = hv_get_bytes_to_write(outring_info);299 300 /*301 * If there is only room for the packet, assume it is full.302 * Otherwise, the next time around, we think the ring buffer303 * is empty since the read index == write index.304 */305 if (bytes_avail_towrite <= totalbytes_towrite) {306 ++channel->out_full_total;307 308 if (!channel->out_full_flag) {309 ++channel->out_full_first;310 channel->out_full_flag = true;311 }312 313 spin_unlock_irqrestore(&outring_info->ring_lock, flags);314 return -EAGAIN;315 }316 317 channel->out_full_flag = false;318 319 /* Write to the ring buffer */320 next_write_location = hv_get_next_write_location(outring_info);321 322 old_write = next_write_location;323 324 for (i = 0; i < kv_count; i++) {325 next_write_location = hv_copyto_ringbuffer(outring_info,326 next_write_location,327 kv_list[i].iov_base,328 kv_list[i].iov_len);329 }330 331 /*332 * Allocate the request ID after the data has been copied into the333 * ring buffer. Once this request ID is allocated, the completion334 * path could find the data and free it.335 */336 337 if (desc->flags == VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED) {338 if (channel->next_request_id_callback != NULL) {339 rqst_id = channel->next_request_id_callback(channel, requestid);340 if (rqst_id == VMBUS_RQST_ERROR) {341 spin_unlock_irqrestore(&outring_info->ring_lock, flags);342 return -EAGAIN;343 }344 }345 }346 desc = hv_get_ring_buffer(outring_info) + old_write;347 __trans_id = (rqst_id == VMBUS_NO_RQSTOR) ? requestid : rqst_id;348 /*349 * Ensure the compiler doesn't generate code that reads the value of350 * the transaction ID from the ring buffer, which is shared with the351 * Hyper-V host and subject to being changed at any time.352 */353 WRITE_ONCE(desc->trans_id, __trans_id);354 if (trans_id)355 *trans_id = __trans_id;356 357 /* Set previous packet start */358 prev_indices = hv_get_ring_bufferindices(outring_info);359 360 next_write_location = hv_copyto_ringbuffer(outring_info,361 next_write_location,362 &prev_indices,363 sizeof(u64));364 365 /* Issue a full memory barrier before updating the write index */366 virt_mb();367 368 /* Now, update the write location */369 hv_set_next_write_location(outring_info, next_write_location);370 371 372 spin_unlock_irqrestore(&outring_info->ring_lock, flags);373 374 hv_signal_on_write(old_write, channel);375 376 if (channel->rescind) {377 if (rqst_id != VMBUS_NO_RQSTOR) {378 /* Reclaim request ID to avoid leak of IDs */379 if (channel->request_addr_callback != NULL)380 channel->request_addr_callback(channel, rqst_id);381 }382 return -ENODEV;383 }384 385 return 0;386}387 388int hv_ringbuffer_read(struct vmbus_channel *channel,389 void *buffer, u32 buflen, u32 *buffer_actual_len,390 u64 *requestid, bool raw)391{392 struct vmpacket_descriptor *desc;393 u32 packetlen, offset;394 395 if (unlikely(buflen == 0))396 return -EINVAL;397 398 *buffer_actual_len = 0;399 *requestid = 0;400 401 /* Make sure there is something to read */402 desc = hv_pkt_iter_first(channel);403 if (desc == NULL) {404 /*405 * No error is set when there is even no header, drivers are406 * supposed to analyze buffer_actual_len.407 */408 return 0;409 }410 411 offset = raw ? 0 : (desc->offset8 << 3);412 packetlen = (desc->len8 << 3) - offset;413 *buffer_actual_len = packetlen;414 *requestid = desc->trans_id;415 416 if (unlikely(packetlen > buflen))417 return -ENOBUFS;418 419 /* since ring is double mapped, only one copy is necessary */420 memcpy(buffer, (const char *)desc + offset, packetlen);421 422 /* Advance ring index to next packet descriptor */423 __hv_pkt_iter_next(channel, desc);424 425 /* Notify host of update */426 hv_pkt_iter_close(channel);427 428 return 0;429}430 431/*432 * Determine number of bytes available in ring buffer after433 * the current iterator (priv_read_index) location.434 *435 * This is similar to hv_get_bytes_to_read but with private436 * read index instead.437 */438static u32 hv_pkt_iter_avail(const struct hv_ring_buffer_info *rbi)439{440 u32 priv_read_loc = rbi->priv_read_index;441 u32 write_loc;442 443 /*444 * The Hyper-V host writes the packet data, then uses445 * store_release() to update the write_index. Use load_acquire()446 * here to prevent loads of the packet data from being re-ordered447 * before the read of the write_index and potentially getting448 * stale data.449 */450 write_loc = virt_load_acquire(&rbi->ring_buffer->write_index);451 452 if (write_loc >= priv_read_loc)453 return write_loc - priv_read_loc;454 else455 return (rbi->ring_datasize - priv_read_loc) + write_loc;456}457 458/*459 * Get first vmbus packet from ring buffer after read_index460 *461 * If ring buffer is empty, returns NULL and no other action needed.462 */463struct vmpacket_descriptor *hv_pkt_iter_first(struct vmbus_channel *channel)464{465 struct hv_ring_buffer_info *rbi = &channel->inbound;466 struct vmpacket_descriptor *desc, *desc_copy;467 u32 bytes_avail, pkt_len, pkt_offset;468 469 hv_debug_delay_test(channel, MESSAGE_DELAY);470 471 bytes_avail = hv_pkt_iter_avail(rbi);472 if (bytes_avail < sizeof(struct vmpacket_descriptor))473 return NULL;474 bytes_avail = min(rbi->pkt_buffer_size, bytes_avail);475 476 desc = (struct vmpacket_descriptor *)(hv_get_ring_buffer(rbi) + rbi->priv_read_index);477 478 /*479 * Ensure the compiler does not use references to incoming Hyper-V values (which480 * could change at any moment) when reading local variables later in the code481 */482 pkt_len = READ_ONCE(desc->len8) << 3;483 pkt_offset = READ_ONCE(desc->offset8) << 3;484 485 /*486 * If pkt_len is invalid, set it to the smaller of hv_pkt_iter_avail() and487 * rbi->pkt_buffer_size488 */489 if (pkt_len < sizeof(struct vmpacket_descriptor) || pkt_len > bytes_avail)490 pkt_len = bytes_avail;491 492 /*493 * If pkt_offset is invalid, arbitrarily set it to494 * the size of vmpacket_descriptor495 */496 if (pkt_offset < sizeof(struct vmpacket_descriptor) || pkt_offset > pkt_len)497 pkt_offset = sizeof(struct vmpacket_descriptor);498 499 /* Copy the Hyper-V packet out of the ring buffer */500 desc_copy = (struct vmpacket_descriptor *)rbi->pkt_buffer;501 memcpy(desc_copy, desc, pkt_len);502 503 /*504 * Hyper-V could still change len8 and offset8 after the earlier read.505 * Ensure that desc_copy has legal values for len8 and offset8 that506 * are consistent with the copy we just made507 */508 desc_copy->len8 = pkt_len >> 3;509 desc_copy->offset8 = pkt_offset >> 3;510 511 return desc_copy;512}513EXPORT_SYMBOL_GPL(hv_pkt_iter_first);514 515/*516 * Get next vmbus packet from ring buffer.517 *518 * Advances the current location (priv_read_index) and checks for more519 * data. If the end of the ring buffer is reached, then return NULL.520 */521struct vmpacket_descriptor *522__hv_pkt_iter_next(struct vmbus_channel *channel,523 const struct vmpacket_descriptor *desc)524{525 struct hv_ring_buffer_info *rbi = &channel->inbound;526 u32 packetlen = desc->len8 << 3;527 u32 dsize = rbi->ring_datasize;528 529 hv_debug_delay_test(channel, MESSAGE_DELAY);530 /* bump offset to next potential packet */531 rbi->priv_read_index += packetlen + VMBUS_PKT_TRAILER;532 if (rbi->priv_read_index >= dsize)533 rbi->priv_read_index -= dsize;534 535 /* more data? */536 return hv_pkt_iter_first(channel);537}538EXPORT_SYMBOL_GPL(__hv_pkt_iter_next);539 540/* How many bytes were read in this iterator cycle */541static u32 hv_pkt_iter_bytes_read(const struct hv_ring_buffer_info *rbi,542 u32 start_read_index)543{544 if (rbi->priv_read_index >= start_read_index)545 return rbi->priv_read_index - start_read_index;546 else547 return rbi->ring_datasize - start_read_index +548 rbi->priv_read_index;549}550 551/*552 * Update host ring buffer after iterating over packets. If the host has553 * stopped queuing new entries because it found the ring buffer full, and554 * sufficient space is being freed up, signal the host. But be careful to555 * only signal the host when necessary, both for performance reasons and556 * because Hyper-V protects itself by throttling guests that signal557 * inappropriately.558 *559 * Determining when to signal is tricky. There are three key data inputs560 * that must be handled in this order to avoid race conditions:561 *562 * 1. Update the read_index563 * 2. Read the pending_send_sz564 * 3. Read the current write_index565 *566 * The interrupt_mask is not used to determine when to signal. The567 * interrupt_mask is used only on the guest->host ring buffer when568 * sending requests to the host. The host does not use it on the host->569 * guest ring buffer to indicate whether it should be signaled.570 */571void hv_pkt_iter_close(struct vmbus_channel *channel)572{573 struct hv_ring_buffer_info *rbi = &channel->inbound;574 u32 curr_write_sz, pending_sz, bytes_read, start_read_index;575 576 /*577 * Make sure all reads are done before we update the read index since578 * the writer may start writing to the read area once the read index579 * is updated.580 */581 virt_rmb();582 start_read_index = rbi->ring_buffer->read_index;583 rbi->ring_buffer->read_index = rbi->priv_read_index;584 585 /*586 * Older versions of Hyper-V (before WS2102 and Win8) do not587 * implement pending_send_sz and simply poll if the host->guest588 * ring buffer is full. No signaling is needed or expected.589 */590 if (!rbi->ring_buffer->feature_bits.feat_pending_send_sz)591 return;592 593 /*594 * Issue a full memory barrier before making the signaling decision.595 * If reading pending_send_sz were to be reordered and happen596 * before we commit the new read_index, a race could occur. If the597 * host were to set the pending_send_sz after we have sampled598 * pending_send_sz, and the ring buffer blocks before we commit the599 * read index, we could miss sending the interrupt. Issue a full600 * memory barrier to address this.601 */602 virt_mb();603 604 /*605 * If the pending_send_sz is zero, then the ring buffer is not606 * blocked and there is no need to signal. This is far by the607 * most common case, so exit quickly for best performance.608 */609 pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);610 if (!pending_sz)611 return;612 613 /*614 * Ensure the read of write_index in hv_get_bytes_to_write()615 * happens after the read of pending_send_sz.616 */617 virt_rmb();618 curr_write_sz = hv_get_bytes_to_write(rbi);619 bytes_read = hv_pkt_iter_bytes_read(rbi, start_read_index);620 621 /*622 * We want to signal the host only if we're transitioning623 * from a "not enough free space" state to a "enough free624 * space" state. For example, it's possible that this function625 * could run and free up enough space to signal the host, and then626 * run again and free up additional space before the host has a627 * chance to clear the pending_send_sz. The 2nd invocation would628 * be a null transition from "enough free space" to "enough free629 * space", which doesn't warrant a signal.630 *631 * Exactly filling the ring buffer is treated as "not enough632 * space". The ring buffer always must have at least one byte633 * empty so the empty and full conditions are distinguishable.634 * hv_get_bytes_to_write() doesn't fully tell the truth in635 * this regard.636 *637 * So first check if we were in the "enough free space" state638 * before we began the iteration. If so, the host was not639 * blocked, and there's no need to signal.640 */641 if (curr_write_sz - bytes_read > pending_sz)642 return;643 644 /*645 * Similarly, if the new state is "not enough space", then646 * there's no need to signal.647 */648 if (curr_write_sz <= pending_sz)649 return;650 651 ++channel->intr_in_full;652 vmbus_setevent(channel);653}654EXPORT_SYMBOL_GPL(hv_pkt_iter_close);655