xref: /qemu/block/export/vhost-user-blk-server.c (revision 4c386f80) 
1 /*
2  * Sharing QEMU block devices via vhost-user protocal
3  *
4  * Parts of the code based on nbd/server.c.
5  *
6  * Copyright (c) Coiby Xu <coiby.xu@gmail.com>.
7  * Copyright (c) 2020 Red Hat, Inc.
8  *
9  * This work is licensed under the terms of the GNU GPL, version 2 or
10  * later.  See the COPYING file in the top-level directory.
11  */
12 #include "qemu/osdep.h"
13 #include "block/block.h"
14 #include "subprojects/libvhost-user/libvhost-user.h" /* only for the type definitions */
15 #include "standard-headers/linux/virtio_blk.h"
16 #include "qemu/vhost-user-server.h"
17 #include "vhost-user-blk-server.h"
18 #include "qapi/error.h"
19 #include "qom/object_interfaces.h"
20 #include "sysemu/block-backend.h"
21 #include "util/block-helpers.h"
22 
23 /*
24  * Sector units are 512 bytes regardless of the
25  * virtio_blk_config->blk_size value.
26  */
27 #define VIRTIO_BLK_SECTOR_BITS 9
28 #define VIRTIO_BLK_SECTOR_SIZE (1ull << VIRTIO_BLK_SECTOR_BITS)
29 
30 enum {
31     VHOST_USER_BLK_NUM_QUEUES_DEFAULT = 1,
32     VHOST_USER_BLK_MAX_DISCARD_SECTORS = 32768,
33     VHOST_USER_BLK_MAX_WRITE_ZEROES_SECTORS = 32768,
34 };
35 struct virtio_blk_inhdr {
36     unsigned char status;
37 };
38 
39 typedef struct VuBlkReq {
40     VuVirtqElement elem;
41     int64_t sector_num;
42     size_t size;
43     struct virtio_blk_inhdr *in;
44     struct virtio_blk_outhdr out;
45     VuServer *server;
46     struct VuVirtq *vq;
47 } VuBlkReq;
48 
49 /* vhost user block device */
50 typedef struct {
51     BlockExport export;
52     VuServer vu_server;
53     uint32_t blk_size;
54     QIOChannelSocket *sioc;
55     struct virtio_blk_config blkcfg;
56     bool writable;
57 } VuBlkExport;
58 
59 static void vu_blk_req_complete(VuBlkReq *req)
60 {
61     VuDev *vu_dev = &req->server->vu_dev;
62 
63     /* IO size with 1 extra status byte */
64     vu_queue_push(vu_dev, req->vq, &req->elem, req->size + 1);
65     vu_queue_notify(vu_dev, req->vq);
66 
67     free(req);
68 }
69 
70 static bool vu_blk_sect_range_ok(VuBlkExport *vexp, uint64_t sector,
71                                  size_t size)
72 {
73     uint64_t nb_sectors = size >> BDRV_SECTOR_BITS;
74     uint64_t total_sectors;
75 
76     if (nb_sectors > BDRV_REQUEST_MAX_SECTORS) {
77         return false;
78     }
79     if ((sector << VIRTIO_BLK_SECTOR_BITS) % vexp->blk_size) {
80         return false;
81     }
82     blk_get_geometry(vexp->export.blk, &total_sectors);
83     if (sector > total_sectors || nb_sectors > total_sectors - sector) {
84         return false;
85     }
86     return true;
87 }
88 
89 static int coroutine_fn
90 vu_blk_discard_write_zeroes(VuBlkExport *vexp, struct iovec *iov,
91                             uint32_t iovcnt, uint32_t type)
92 {
93     BlockBackend *blk = vexp->export.blk;
94     struct virtio_blk_discard_write_zeroes desc;
95     ssize_t size;
96     uint64_t sector;
97     uint32_t num_sectors;
98     uint32_t max_sectors;
99     uint32_t flags;
100     int bytes;
101 
102     /* Only one desc is currently supported */
103     if (unlikely(iov_size(iov, iovcnt) > sizeof(desc))) {
104         return VIRTIO_BLK_S_UNSUPP;
105     }
106 
107     size = iov_to_buf(iov, iovcnt, 0, &desc, sizeof(desc));
108     if (unlikely(size != sizeof(desc))) {
109         error_report("Invalid size %zd, expected %zu", size, sizeof(desc));
110         return VIRTIO_BLK_S_IOERR;
111     }
112 
113     sector = le64_to_cpu(desc.sector);
114     num_sectors = le32_to_cpu(desc.num_sectors);
115     flags = le32_to_cpu(desc.flags);
116     max_sectors = (type == VIRTIO_BLK_T_WRITE_ZEROES) ?
117                   VHOST_USER_BLK_MAX_WRITE_ZEROES_SECTORS :
118                   VHOST_USER_BLK_MAX_DISCARD_SECTORS;
119 
120     /* This check ensures that 'bytes' fits in an int */
121     if (unlikely(num_sectors > max_sectors)) {
122         return VIRTIO_BLK_S_IOERR;
123     }
124 
125     bytes = num_sectors << VIRTIO_BLK_SECTOR_BITS;
126 
127     if (unlikely(!vu_blk_sect_range_ok(vexp, sector, bytes))) {
128         return VIRTIO_BLK_S_IOERR;
129     }
130 
131     /*
132      * The device MUST set the status byte to VIRTIO_BLK_S_UNSUPP for discard
133      * and write zeroes commands if any unknown flag is set.
134      */
135     if (unlikely(flags & ~VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP)) {
136         return VIRTIO_BLK_S_UNSUPP;
137     }
138 
139     if (type == VIRTIO_BLK_T_WRITE_ZEROES) {
140         int blk_flags = 0;
141 
142         if (flags & VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP) {
143             blk_flags |= BDRV_REQ_MAY_UNMAP;
144         }
145 
146         if (blk_co_pwrite_zeroes(blk, sector << VIRTIO_BLK_SECTOR_BITS,
147                                  bytes, blk_flags) == 0) {
148             return VIRTIO_BLK_S_OK;
149         }
150     } else if (type == VIRTIO_BLK_T_DISCARD) {
151         /*
152          * The device MUST set the status byte to VIRTIO_BLK_S_UNSUPP for
153          * discard commands if the unmap flag is set.
154          */
155         if (unlikely(flags & VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP)) {
156             return VIRTIO_BLK_S_UNSUPP;
157         }
158 
159         if (blk_co_pdiscard(blk, sector << VIRTIO_BLK_SECTOR_BITS,
160                             bytes) == 0) {
161             return VIRTIO_BLK_S_OK;
162         }
163     }
164 
165     return VIRTIO_BLK_S_IOERR;
166 }
167 
168 static void coroutine_fn vu_blk_virtio_process_req(void *opaque)
169 {
170     VuBlkReq *req = opaque;
171     VuServer *server = req->server;
172     VuVirtqElement *elem = &req->elem;
173     uint32_t type;
174 
175     VuBlkExport *vexp = container_of(server, VuBlkExport, vu_server);
176     BlockBackend *blk = vexp->export.blk;
177 
178     struct iovec *in_iov = elem->in_sg;
179     struct iovec *out_iov = elem->out_sg;
180     unsigned in_num = elem->in_num;
181     unsigned out_num = elem->out_num;
182 
183     /* refer to hw/block/virtio_blk.c */
184     if (elem->out_num < 1 || elem->in_num < 1) {
185         error_report("virtio-blk request missing headers");
186         goto err;
187     }
188 
189     if (unlikely(iov_to_buf(out_iov, out_num, 0, &req->out,
190                             sizeof(req->out)) != sizeof(req->out))) {
191         error_report("virtio-blk request outhdr too short");
192         goto err;
193     }
194 
195     iov_discard_front(&out_iov, &out_num, sizeof(req->out));
196 
197     if (in_iov[in_num - 1].iov_len < sizeof(struct virtio_blk_inhdr)) {
198         error_report("virtio-blk request inhdr too short");
199         goto err;
200     }
201 
202     /* We always touch the last byte, so just see how big in_iov is.  */
203     req->in = (void *)in_iov[in_num - 1].iov_base
204               + in_iov[in_num - 1].iov_len
205               - sizeof(struct virtio_blk_inhdr);
206     iov_discard_back(in_iov, &in_num, sizeof(struct virtio_blk_inhdr));
207 
208     type = le32_to_cpu(req->out.type);
209     switch (type & ~VIRTIO_BLK_T_BARRIER) {
210     case VIRTIO_BLK_T_IN:
211     case VIRTIO_BLK_T_OUT: {
212         QEMUIOVector qiov;
213         int64_t offset;
214         ssize_t ret = 0;
215         bool is_write = type & VIRTIO_BLK_T_OUT;
216         req->sector_num = le64_to_cpu(req->out.sector);
217 
218         if (is_write && !vexp->writable) {
219             req->in->status = VIRTIO_BLK_S_IOERR;
220             break;
221         }
222 
223         if (is_write) {
224             qemu_iovec_init_external(&qiov, out_iov, out_num);
225         } else {
226             qemu_iovec_init_external(&qiov, in_iov, in_num);
227         }
228 
229         if (unlikely(!vu_blk_sect_range_ok(vexp,
230                                            req->sector_num,
231                                            qiov.size))) {
232             req->in->status = VIRTIO_BLK_S_IOERR;
233             break;
234         }
235 
236         offset = req->sector_num << VIRTIO_BLK_SECTOR_BITS;
237 
238         if (is_write) {
239             ret = blk_co_pwritev(blk, offset, qiov.size, &qiov, 0);
240         } else {
241             ret = blk_co_preadv(blk, offset, qiov.size, &qiov, 0);
242         }
243         if (ret >= 0) {
244             req->in->status = VIRTIO_BLK_S_OK;
245         } else {
246             req->in->status = VIRTIO_BLK_S_IOERR;
247         }
248         break;
249     }
250     case VIRTIO_BLK_T_FLUSH:
251         if (blk_co_flush(blk) == 0) {
252             req->in->status = VIRTIO_BLK_S_OK;
253         } else {
254             req->in->status = VIRTIO_BLK_S_IOERR;
255         }
256         break;
257     case VIRTIO_BLK_T_GET_ID: {
258         size_t size = MIN(iov_size(&elem->in_sg[0], in_num),
259                           VIRTIO_BLK_ID_BYTES);
260         snprintf(elem->in_sg[0].iov_base, size, "%s", "vhost_user_blk");
261         req->in->status = VIRTIO_BLK_S_OK;
262         req->size = elem->in_sg[0].iov_len;
263         break;
264     }
265     case VIRTIO_BLK_T_DISCARD:
266     case VIRTIO_BLK_T_WRITE_ZEROES: {
267         if (!vexp->writable) {
268             req->in->status = VIRTIO_BLK_S_IOERR;
269             break;
270         }
271 
272         req->in->status = vu_blk_discard_write_zeroes(vexp, out_iov, out_num,
273                                                       type);
274         break;
275     }
276     default:
277         req->in->status = VIRTIO_BLK_S_UNSUPP;
278         break;
279     }
280 
281     vu_blk_req_complete(req);
282     return;
283 
284 err:
285     free(req);
286 }
287 
288 static void vu_blk_process_vq(VuDev *vu_dev, int idx)
289 {
290     VuServer *server = container_of(vu_dev, VuServer, vu_dev);
291     VuVirtq *vq = vu_get_queue(vu_dev, idx);
292 
293     while (1) {
294         VuBlkReq *req;
295 
296         req = vu_queue_pop(vu_dev, vq, sizeof(VuBlkReq));
297         if (!req) {
298             break;
299         }
300 
301         req->server = server;
302         req->vq = vq;
303 
304         Coroutine *co =
305             qemu_coroutine_create(vu_blk_virtio_process_req, req);
306         qemu_coroutine_enter(co);
307     }
308 }
309 
310 static void vu_blk_queue_set_started(VuDev *vu_dev, int idx, bool started)
311 {
312     VuVirtq *vq;
313 
314     assert(vu_dev);
315 
316     vq = vu_get_queue(vu_dev, idx);
317     vu_set_queue_handler(vu_dev, vq, started ? vu_blk_process_vq : NULL);
318 }
319 
320 static uint64_t vu_blk_get_features(VuDev *dev)
321 {
322     uint64_t features;
323     VuServer *server = container_of(dev, VuServer, vu_dev);
324     VuBlkExport *vexp = container_of(server, VuBlkExport, vu_server);
325     features = 1ull << VIRTIO_BLK_F_SIZE_MAX |
326                1ull << VIRTIO_BLK_F_SEG_MAX |
327                1ull << VIRTIO_BLK_F_TOPOLOGY |
328                1ull << VIRTIO_BLK_F_BLK_SIZE |
329                1ull << VIRTIO_BLK_F_FLUSH |
330                1ull << VIRTIO_BLK_F_DISCARD |
331                1ull << VIRTIO_BLK_F_WRITE_ZEROES |
332                1ull << VIRTIO_BLK_F_CONFIG_WCE |
333                1ull << VIRTIO_BLK_F_MQ |
334                1ull << VIRTIO_F_VERSION_1 |
335                1ull << VIRTIO_RING_F_INDIRECT_DESC |
336                1ull << VIRTIO_RING_F_EVENT_IDX |
337                1ull << VHOST_USER_F_PROTOCOL_FEATURES;
338 
339     if (!vexp->writable) {
340         features |= 1ull << VIRTIO_BLK_F_RO;
341     }
342 
343     return features;
344 }
345 
346 static uint64_t vu_blk_get_protocol_features(VuDev *dev)
347 {
348     return 1ull << VHOST_USER_PROTOCOL_F_CONFIG;
349 }
350 
351 static int
352 vu_blk_get_config(VuDev *vu_dev, uint8_t *config, uint32_t len)
353 {
354     VuServer *server = container_of(vu_dev, VuServer, vu_dev);
355     VuBlkExport *vexp = container_of(server, VuBlkExport, vu_server);
356 
357     if (len > sizeof(struct virtio_blk_config)) {
358         return -1;
359     }
360 
361     memcpy(config, &vexp->blkcfg, len);
362     return 0;
363 }
364 
365 static int
366 vu_blk_set_config(VuDev *vu_dev, const uint8_t *data,
367                     uint32_t offset, uint32_t size, uint32_t flags)
368 {
369     VuServer *server = container_of(vu_dev, VuServer, vu_dev);
370     VuBlkExport *vexp = container_of(server, VuBlkExport, vu_server);
371     uint8_t wce;
372 
373     /* don't support live migration */
374     if (flags != VHOST_SET_CONFIG_TYPE_MASTER) {
375         return -EINVAL;
376     }
377 
378     if (offset != offsetof(struct virtio_blk_config, wce) ||
379         size != 1) {
380         return -EINVAL;
381     }
382 
383     wce = *data;
384     vexp->blkcfg.wce = wce;
385     blk_set_enable_write_cache(vexp->export.blk, wce);
386     return 0;
387 }
388 
389 /*
390  * When the client disconnects, it sends a VHOST_USER_NONE request
391  * and vu_process_message will simple call exit which cause the VM
392  * to exit abruptly.
393  * To avoid this issue,  process VHOST_USER_NONE request ahead
394  * of vu_process_message.
395  *
396  */
397 static int vu_blk_process_msg(VuDev *dev, VhostUserMsg *vmsg, int *do_reply)
398 {
399     if (vmsg->request == VHOST_USER_NONE) {
400         dev->panic(dev, "disconnect");
401         return true;
402     }
403     return false;
404 }
405 
406 static const VuDevIface vu_blk_iface = {
407     .get_features          = vu_blk_get_features,
408     .queue_set_started     = vu_blk_queue_set_started,
409     .get_protocol_features = vu_blk_get_protocol_features,
410     .get_config            = vu_blk_get_config,
411     .set_config            = vu_blk_set_config,
412     .process_msg           = vu_blk_process_msg,
413 };
414 
415 static void blk_aio_attached(AioContext *ctx, void *opaque)
416 {
417     VuBlkExport *vexp = opaque;
418 
419     vexp->export.ctx = ctx;
420     vhost_user_server_attach_aio_context(&vexp->vu_server, ctx);
421 }
422 
423 static void blk_aio_detach(void *opaque)
424 {
425     VuBlkExport *vexp = opaque;
426 
427     vhost_user_server_detach_aio_context(&vexp->vu_server);
428     vexp->export.ctx = NULL;
429 }
430 
431 static void
432 vu_blk_initialize_config(BlockDriverState *bs,
433                          struct virtio_blk_config *config,
434                          uint32_t blk_size,
435                          uint16_t num_queues)
436 {
437     config->capacity =
438         cpu_to_le64(bdrv_getlength(bs) >> VIRTIO_BLK_SECTOR_BITS);
439     config->blk_size = cpu_to_le32(blk_size);
440     config->size_max = cpu_to_le32(0);
441     config->seg_max = cpu_to_le32(128 - 2);
442     config->min_io_size = cpu_to_le16(1);
443     config->opt_io_size = cpu_to_le32(1);
444     config->num_queues = cpu_to_le16(num_queues);
445     config->max_discard_sectors =
446         cpu_to_le32(VHOST_USER_BLK_MAX_DISCARD_SECTORS);
447     config->max_discard_seg = cpu_to_le32(1);
448     config->discard_sector_alignment =
449         cpu_to_le32(blk_size >> VIRTIO_BLK_SECTOR_BITS);
450     config->max_write_zeroes_sectors
451         = cpu_to_le32(VHOST_USER_BLK_MAX_WRITE_ZEROES_SECTORS);
452     config->max_write_zeroes_seg = cpu_to_le32(1);
453 }
454 
455 static void vu_blk_exp_request_shutdown(BlockExport *exp)
456 {
457     VuBlkExport *vexp = container_of(exp, VuBlkExport, export);
458 
459     vhost_user_server_stop(&vexp->vu_server);
460 }
461 
462 static int vu_blk_exp_create(BlockExport *exp, BlockExportOptions *opts,
463                              Error **errp)
464 {
465     VuBlkExport *vexp = container_of(exp, VuBlkExport, export);
466     BlockExportOptionsVhostUserBlk *vu_opts = &opts->u.vhost_user_blk;
467     Error *local_err = NULL;
468     uint64_t logical_block_size;
469     uint16_t num_queues = VHOST_USER_BLK_NUM_QUEUES_DEFAULT;
470 
471     vexp->writable = opts->writable;
472     vexp->blkcfg.wce = 0;
473 
474     if (vu_opts->has_logical_block_size) {
475         logical_block_size = vu_opts->logical_block_size;
476     } else {
477         logical_block_size = VIRTIO_BLK_SECTOR_SIZE;
478     }
479     check_block_size(exp->id, "logical-block-size", logical_block_size,
480                      &local_err);
481     if (local_err) {
482         error_propagate(errp, local_err);
483         return -EINVAL;
484     }
485     vexp->blk_size = logical_block_size;
486     blk_set_guest_block_size(exp->blk, logical_block_size);
487 
488     if (vu_opts->has_num_queues) {
489         num_queues = vu_opts->num_queues;
490     }
491     if (num_queues == 0) {
492         error_setg(errp, "num-queues must be greater than 0");
493         return -EINVAL;
494     }
495 
496     vu_blk_initialize_config(blk_bs(exp->blk), &vexp->blkcfg,
497                              logical_block_size, num_queues);
498 
499     blk_add_aio_context_notifier(exp->blk, blk_aio_attached, blk_aio_detach,
500                                  vexp);
501 
502     if (!vhost_user_server_start(&vexp->vu_server, vu_opts->addr, exp->ctx,
503                                  num_queues, &vu_blk_iface, errp)) {
504         blk_remove_aio_context_notifier(exp->blk, blk_aio_attached,
505                                         blk_aio_detach, vexp);
506         return -EADDRNOTAVAIL;
507     }
508 
509     return 0;
510 }
511 
512 static void vu_blk_exp_delete(BlockExport *exp)
513 {
514     VuBlkExport *vexp = container_of(exp, VuBlkExport, export);
515 
516     blk_remove_aio_context_notifier(exp->blk, blk_aio_attached, blk_aio_detach,
517                                     vexp);
518 }
519 
520 const BlockExportDriver blk_exp_vhost_user_blk = {
521     .type               = BLOCK_EXPORT_TYPE_VHOST_USER_BLK,
522     .instance_size      = sizeof(VuBlkExport),
523     .create             = vu_blk_exp_create,
524     .delete             = vu_blk_exp_delete,
525     .request_shutdown   = vu_blk_exp_request_shutdown,
526 };
527