linux/drivers/virtio/virtio_ring.c
<<
>>
Prefs
   1/* Virtio ring implementation.
   2 *
   3 *  Copyright 2007 Rusty Russell IBM Corporation
   4 *
   5 *  This program is free software; you can redistribute it and/or modify
   6 *  it under the terms of the GNU General Public License as published by
   7 *  the Free Software Foundation; either version 2 of the License, or
   8 *  (at your option) any later version.
   9 *
  10 *  This program is distributed in the hope that it will be useful,
  11 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 *  GNU General Public License for more details.
  14 *
  15 *  You should have received a copy of the GNU General Public License
  16 *  along with this program; if not, write to the Free Software
  17 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  18 */
  19#include <linux/virtio.h>
  20#include <linux/virtio_ring.h>
  21#include <linux/virtio_config.h>
  22#include <linux/device.h>
  23#include <linux/slab.h>
  24#include <linux/module.h>
  25#include <linux/hrtimer.h>
  26
  27/* virtio guest is communicating with a virtual "device" that actually runs on
  28 * a host processor.  Memory barriers are used to control SMP effects. */
  29#ifdef CONFIG_SMP
  30/* Where possible, use SMP barriers which are more lightweight than mandatory
  31 * barriers, because mandatory barriers control MMIO effects on accesses
  32 * through relaxed memory I/O windows (which virtio-pci does not use). */
  33#define virtio_mb(vq) \
  34        do { if ((vq)->weak_barriers) smp_mb(); else mb(); } while(0)
  35#define virtio_rmb(vq) \
  36        do { if ((vq)->weak_barriers) smp_rmb(); else rmb(); } while(0)
  37#define virtio_wmb(vq) \
  38        do { if ((vq)->weak_barriers) smp_wmb(); else wmb(); } while(0)
  39#else
  40/* We must force memory ordering even if guest is UP since host could be
  41 * running on another CPU, but SMP barriers are defined to barrier() in that
  42 * configuration. So fall back to mandatory barriers instead. */
  43#define virtio_mb(vq) mb()
  44#define virtio_rmb(vq) rmb()
  45#define virtio_wmb(vq) wmb()
  46#endif
  47
  48#ifdef DEBUG
  49/* For development, we want to crash whenever the ring is screwed. */
  50#define BAD_RING(_vq, fmt, args...)                             \
  51        do {                                                    \
  52                dev_err(&(_vq)->vq.vdev->dev,                   \
  53                        "%s:"fmt, (_vq)->vq.name, ##args);      \
  54                BUG();                                          \
  55        } while (0)
  56/* Caller is supposed to guarantee no reentry. */
  57#define START_USE(_vq)                                          \
  58        do {                                                    \
  59                if ((_vq)->in_use)                              \
  60                        panic("%s:in_use = %i\n",               \
  61                              (_vq)->vq.name, (_vq)->in_use);   \
  62                (_vq)->in_use = __LINE__;                       \
  63        } while (0)
  64#define END_USE(_vq) \
  65        do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } while(0)
  66#else
  67#define BAD_RING(_vq, fmt, args...)                             \
  68        do {                                                    \
  69                dev_err(&_vq->vq.vdev->dev,                     \
  70                        "%s:"fmt, (_vq)->vq.name, ##args);      \
  71                (_vq)->broken = true;                           \
  72        } while (0)
  73#define START_USE(vq)
  74#define END_USE(vq)
  75#endif
  76
  77struct vring_virtqueue
  78{
  79        struct virtqueue vq;
  80
  81        /* Actual memory layout for this queue */
  82        struct vring vring;
  83
  84        /* Can we use weak barriers? */
  85        bool weak_barriers;
  86
  87        /* Other side has made a mess, don't try any more. */
  88        bool broken;
  89
  90        /* Host supports indirect buffers */
  91        bool indirect;
  92
  93        /* Host publishes avail event idx */
  94        bool event;
  95
  96        /* Number of free buffers */
  97        unsigned int num_free;
  98        /* Head of free buffer list. */
  99        unsigned int free_head;
 100        /* Number we've added since last sync. */
 101        unsigned int num_added;
 102
 103        /* Last used index we've seen. */
 104        u16 last_used_idx;
 105
 106        /* How to notify other side. FIXME: commonalize hcalls! */
 107        void (*notify)(struct virtqueue *vq);
 108
 109        /* Index of the queue */
 110        int queue_index;
 111
 112#ifdef DEBUG
 113        /* They're supposed to lock for us. */
 114        unsigned int in_use;
 115
 116        /* Figure out if their kicks are too delayed. */
 117        bool last_add_time_valid;
 118        ktime_t last_add_time;
 119#endif
 120
 121        /* Tokens for callbacks. */
 122        void *data[];
 123};
 124
 125#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
 126
 127/* Set up an indirect table of descriptors and add it to the queue. */
 128static int vring_add_indirect(struct vring_virtqueue *vq,
 129                              struct scatterlist sg[],
 130                              unsigned int out,
 131                              unsigned int in,
 132                              gfp_t gfp)
 133{
 134        struct vring_desc *desc;
 135        unsigned head;
 136        int i;
 137
 138        desc = kmalloc((out + in) * sizeof(struct vring_desc), gfp);
 139        if (!desc)
 140                return -ENOMEM;
 141
 142        /* Transfer entries from the sg list into the indirect page */
 143        for (i = 0; i < out; i++) {
 144                desc[i].flags = VRING_DESC_F_NEXT;
 145                desc[i].addr = sg_phys(sg);
 146                desc[i].len = sg->length;
 147                desc[i].next = i+1;
 148                sg++;
 149        }
 150        for (; i < (out + in); i++) {
 151                desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
 152                desc[i].addr = sg_phys(sg);
 153                desc[i].len = sg->length;
 154                desc[i].next = i+1;
 155                sg++;
 156        }
 157
 158        /* Last one doesn't continue. */
 159        desc[i-1].flags &= ~VRING_DESC_F_NEXT;
 160        desc[i-1].next = 0;
 161
 162        /* We're about to use a buffer */
 163        vq->num_free--;
 164
 165        /* Use a single buffer which doesn't continue */
 166        head = vq->free_head;
 167        vq->vring.desc[head].flags = VRING_DESC_F_INDIRECT;
 168        vq->vring.desc[head].addr = virt_to_phys(desc);
 169        vq->vring.desc[head].len = i * sizeof(struct vring_desc);
 170
 171        /* Update free pointer */
 172        vq->free_head = vq->vring.desc[head].next;
 173
 174        return head;
 175}
 176
 177int virtqueue_get_queue_index(struct virtqueue *_vq)
 178{
 179        struct vring_virtqueue *vq = to_vvq(_vq);
 180        return vq->queue_index;
 181}
 182EXPORT_SYMBOL_GPL(virtqueue_get_queue_index);
 183
 184/**
 185 * virtqueue_add_buf - expose buffer to other end
 186 * @vq: the struct virtqueue we're talking about.
 187 * @sg: the description of the buffer(s).
 188 * @out_num: the number of sg readable by other side
 189 * @in_num: the number of sg which are writable (after readable ones)
 190 * @data: the token identifying the buffer.
 191 * @gfp: how to do memory allocations (if necessary).
 192 *
 193 * Caller must ensure we don't call this with other virtqueue operations
 194 * at the same time (except where noted).
 195 *
 196 * Returns remaining capacity of queue or a negative error
 197 * (ie. ENOSPC).  Note that it only really makes sense to treat all
 198 * positive return values as "available": indirect buffers mean that
 199 * we can put an entire sg[] array inside a single queue entry.
 200 */
 201int virtqueue_add_buf(struct virtqueue *_vq,
 202                      struct scatterlist sg[],
 203                      unsigned int out,
 204                      unsigned int in,
 205                      void *data,
 206                      gfp_t gfp)
 207{
 208        struct vring_virtqueue *vq = to_vvq(_vq);
 209        unsigned int i, avail, uninitialized_var(prev);
 210        int head;
 211
 212        START_USE(vq);
 213
 214        BUG_ON(data == NULL);
 215
 216#ifdef DEBUG
 217        {
 218                ktime_t now = ktime_get();
 219
 220                /* No kick or get, with .1 second between?  Warn. */
 221                if (vq->last_add_time_valid)
 222                        WARN_ON(ktime_to_ms(ktime_sub(now, vq->last_add_time))
 223                                            > 100);
 224                vq->last_add_time = now;
 225                vq->last_add_time_valid = true;
 226        }
 227#endif
 228
 229        /* If the host supports indirect descriptor tables, and we have multiple
 230         * buffers, then go indirect. FIXME: tune this threshold */
 231        if (vq->indirect && (out + in) > 1 && vq->num_free) {
 232                head = vring_add_indirect(vq, sg, out, in, gfp);
 233                if (likely(head >= 0))
 234                        goto add_head;
 235        }
 236
 237        BUG_ON(out + in > vq->vring.num);
 238        BUG_ON(out + in == 0);
 239
 240        if (vq->num_free < out + in) {
 241                pr_debug("Can't add buf len %i - avail = %i\n",
 242                         out + in, vq->num_free);
 243                /* FIXME: for historical reasons, we force a notify here if
 244                 * there are outgoing parts to the buffer.  Presumably the
 245                 * host should service the ring ASAP. */
 246                if (out)
 247                        vq->notify(&vq->vq);
 248                END_USE(vq);
 249                return -ENOSPC;
 250        }
 251
 252        /* We're about to use some buffers from the free list. */
 253        vq->num_free -= out + in;
 254
 255        head = vq->free_head;
 256        for (i = vq->free_head; out; i = vq->vring.desc[i].next, out--) {
 257                vq->vring.desc[i].flags = VRING_DESC_F_NEXT;
 258                vq->vring.desc[i].addr = sg_phys(sg);
 259                vq->vring.desc[i].len = sg->length;
 260                prev = i;
 261                sg++;
 262        }
 263        for (; in; i = vq->vring.desc[i].next, in--) {
 264                vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
 265                vq->vring.desc[i].addr = sg_phys(sg);
 266                vq->vring.desc[i].len = sg->length;
 267                prev = i;
 268                sg++;
 269        }
 270        /* Last one doesn't continue. */
 271        vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT;
 272
 273        /* Update free pointer */
 274        vq->free_head = i;
 275
 276add_head:
 277        /* Set token. */
 278        vq->data[head] = data;
 279
 280        /* Put entry in available array (but don't update avail->idx until they
 281         * do sync). */
 282        avail = (vq->vring.avail->idx & (vq->vring.num-1));
 283        vq->vring.avail->ring[avail] = head;
 284
 285        /* Descriptors and available array need to be set before we expose the
 286         * new available array entries. */
 287        virtio_wmb(vq);
 288        vq->vring.avail->idx++;
 289        vq->num_added++;
 290
 291        /* This is very unlikely, but theoretically possible.  Kick
 292         * just in case. */
 293        if (unlikely(vq->num_added == (1 << 16) - 1))
 294                virtqueue_kick(_vq);
 295
 296        pr_debug("Added buffer head %i to %p\n", head, vq);
 297        END_USE(vq);
 298
 299        return vq->num_free;
 300}
 301EXPORT_SYMBOL_GPL(virtqueue_add_buf);
 302
 303/**
 304 * virtqueue_kick_prepare - first half of split virtqueue_kick call.
 305 * @vq: the struct virtqueue
 306 *
 307 * Instead of virtqueue_kick(), you can do:
 308 *      if (virtqueue_kick_prepare(vq))
 309 *              virtqueue_notify(vq);
 310 *
 311 * This is sometimes useful because the virtqueue_kick_prepare() needs
 312 * to be serialized, but the actual virtqueue_notify() call does not.
 313 */
 314bool virtqueue_kick_prepare(struct virtqueue *_vq)
 315{
 316        struct vring_virtqueue *vq = to_vvq(_vq);
 317        u16 new, old;
 318        bool needs_kick;
 319
 320        START_USE(vq);
 321        /* We need to expose available array entries before checking avail
 322         * event. */
 323        virtio_mb(vq);
 324
 325        old = vq->vring.avail->idx - vq->num_added;
 326        new = vq->vring.avail->idx;
 327        vq->num_added = 0;
 328
 329#ifdef DEBUG
 330        if (vq->last_add_time_valid) {
 331                WARN_ON(ktime_to_ms(ktime_sub(ktime_get(),
 332                                              vq->last_add_time)) > 100);
 333        }
 334        vq->last_add_time_valid = false;
 335#endif
 336
 337        if (vq->event) {
 338                needs_kick = vring_need_event(vring_avail_event(&vq->vring),
 339                                              new, old);
 340        } else {
 341                needs_kick = !(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY);
 342        }
 343        END_USE(vq);
 344        return needs_kick;
 345}
 346EXPORT_SYMBOL_GPL(virtqueue_kick_prepare);
 347
 348/**
 349 * virtqueue_notify - second half of split virtqueue_kick call.
 350 * @vq: the struct virtqueue
 351 *
 352 * This does not need to be serialized.
 353 */
 354void virtqueue_notify(struct virtqueue *_vq)
 355{
 356        struct vring_virtqueue *vq = to_vvq(_vq);
 357
 358        /* Prod other side to tell it about changes. */
 359        vq->notify(_vq);
 360}
 361EXPORT_SYMBOL_GPL(virtqueue_notify);
 362
 363/**
 364 * virtqueue_kick - update after add_buf
 365 * @vq: the struct virtqueue
 366 *
 367 * After one or more virtqueue_add_buf calls, invoke this to kick
 368 * the other side.
 369 *
 370 * Caller must ensure we don't call this with other virtqueue
 371 * operations at the same time (except where noted).
 372 */
 373void virtqueue_kick(struct virtqueue *vq)
 374{
 375        if (virtqueue_kick_prepare(vq))
 376                virtqueue_notify(vq);
 377}
 378EXPORT_SYMBOL_GPL(virtqueue_kick);
 379
 380static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
 381{
 382        unsigned int i;
 383
 384        /* Clear data ptr. */
 385        vq->data[head] = NULL;
 386
 387        /* Put back on free list: find end */
 388        i = head;
 389
 390        /* Free the indirect table */
 391        if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT)
 392                kfree(phys_to_virt(vq->vring.desc[i].addr));
 393
 394        while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) {
 395                i = vq->vring.desc[i].next;
 396                vq->num_free++;
 397        }
 398
 399        vq->vring.desc[i].next = vq->free_head;
 400        vq->free_head = head;
 401        /* Plus final descriptor */
 402        vq->num_free++;
 403}
 404
 405static inline bool more_used(const struct vring_virtqueue *vq)
 406{
 407        return vq->last_used_idx != vq->vring.used->idx;
 408}
 409
 410/**
 411 * virtqueue_get_buf - get the next used buffer
 412 * @vq: the struct virtqueue we're talking about.
 413 * @len: the length written into the buffer
 414 *
 415 * If the driver wrote data into the buffer, @len will be set to the
 416 * amount written.  This means you don't need to clear the buffer
 417 * beforehand to ensure there's no data leakage in the case of short
 418 * writes.
 419 *
 420 * Caller must ensure we don't call this with other virtqueue
 421 * operations at the same time (except where noted).
 422 *
 423 * Returns NULL if there are no used buffers, or the "data" token
 424 * handed to virtqueue_add_buf().
 425 */
 426void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
 427{
 428        struct vring_virtqueue *vq = to_vvq(_vq);
 429        void *ret;
 430        unsigned int i;
 431        u16 last_used;
 432
 433        START_USE(vq);
 434
 435        if (unlikely(vq->broken)) {
 436                END_USE(vq);
 437                return NULL;
 438        }
 439
 440        if (!more_used(vq)) {
 441                pr_debug("No more buffers in queue\n");
 442                END_USE(vq);
 443                return NULL;
 444        }
 445
 446        /* Only get used array entries after they have been exposed by host. */
 447        virtio_rmb(vq);
 448
 449        last_used = (vq->last_used_idx & (vq->vring.num - 1));
 450        i = vq->vring.used->ring[last_used].id;
 451        *len = vq->vring.used->ring[last_used].len;
 452
 453        if (unlikely(i >= vq->vring.num)) {
 454                BAD_RING(vq, "id %u out of range\n", i);
 455                return NULL;
 456        }
 457        if (unlikely(!vq->data[i])) {
 458                BAD_RING(vq, "id %u is not a head!\n", i);
 459                return NULL;
 460        }
 461
 462        /* detach_buf clears data, so grab it now. */
 463        ret = vq->data[i];
 464        detach_buf(vq, i);
 465        vq->last_used_idx++;
 466        /* If we expect an interrupt for the next entry, tell host
 467         * by writing event index and flush out the write before
 468         * the read in the next get_buf call. */
 469        if (!(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)) {
 470                vring_used_event(&vq->vring) = vq->last_used_idx;
 471                virtio_mb(vq);
 472        }
 473
 474#ifdef DEBUG
 475        vq->last_add_time_valid = false;
 476#endif
 477
 478        END_USE(vq);
 479        return ret;
 480}
 481EXPORT_SYMBOL_GPL(virtqueue_get_buf);
 482
 483/**
 484 * virtqueue_disable_cb - disable callbacks
 485 * @vq: the struct virtqueue we're talking about.
 486 *
 487 * Note that this is not necessarily synchronous, hence unreliable and only
 488 * useful as an optimization.
 489 *
 490 * Unlike other operations, this need not be serialized.
 491 */
 492void virtqueue_disable_cb(struct virtqueue *_vq)
 493{
 494        struct vring_virtqueue *vq = to_vvq(_vq);
 495
 496        vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
 497}
 498EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
 499
 500/**
 501 * virtqueue_enable_cb - restart callbacks after disable_cb.
 502 * @vq: the struct virtqueue we're talking about.
 503 *
 504 * This re-enables callbacks; it returns "false" if there are pending
 505 * buffers in the queue, to detect a possible race between the driver
 506 * checking for more work, and enabling callbacks.
 507 *
 508 * Caller must ensure we don't call this with other virtqueue
 509 * operations at the same time (except where noted).
 510 */
 511bool virtqueue_enable_cb(struct virtqueue *_vq)
 512{
 513        struct vring_virtqueue *vq = to_vvq(_vq);
 514
 515        START_USE(vq);
 516
 517        /* We optimistically turn back on interrupts, then check if there was
 518         * more to do. */
 519        /* Depending on the VIRTIO_RING_F_EVENT_IDX feature, we need to
 520         * either clear the flags bit or point the event index at the next
 521         * entry. Always do both to keep code simple. */
 522        vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
 523        vring_used_event(&vq->vring) = vq->last_used_idx;
 524        virtio_mb(vq);
 525        if (unlikely(more_used(vq))) {
 526                END_USE(vq);
 527                return false;
 528        }
 529
 530        END_USE(vq);
 531        return true;
 532}
 533EXPORT_SYMBOL_GPL(virtqueue_enable_cb);
 534
 535/**
 536 * virtqueue_enable_cb_delayed - restart callbacks after disable_cb.
 537 * @vq: the struct virtqueue we're talking about.
 538 *
 539 * This re-enables callbacks but hints to the other side to delay
 540 * interrupts until most of the available buffers have been processed;
 541 * it returns "false" if there are many pending buffers in the queue,
 542 * to detect a possible race between the driver checking for more work,
 543 * and enabling callbacks.
 544 *
 545 * Caller must ensure we don't call this with other virtqueue
 546 * operations at the same time (except where noted).
 547 */
 548bool virtqueue_enable_cb_delayed(struct virtqueue *_vq)
 549{
 550        struct vring_virtqueue *vq = to_vvq(_vq);
 551        u16 bufs;
 552
 553        START_USE(vq);
 554
 555        /* We optimistically turn back on interrupts, then check if there was
 556         * more to do. */
 557        /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to
 558         * either clear the flags bit or point the event index at the next
 559         * entry. Always do both to keep code simple. */
 560        vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
 561        /* TODO: tune this threshold */
 562        bufs = (u16)(vq->vring.avail->idx - vq->last_used_idx) * 3 / 4;
 563        vring_used_event(&vq->vring) = vq->last_used_idx + bufs;
 564        virtio_mb(vq);
 565        if (unlikely((u16)(vq->vring.used->idx - vq->last_used_idx) > bufs)) {
 566                END_USE(vq);
 567                return false;
 568        }
 569
 570        END_USE(vq);
 571        return true;
 572}
 573EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed);
 574
 575/**
 576 * virtqueue_detach_unused_buf - detach first unused buffer
 577 * @vq: the struct virtqueue we're talking about.
 578 *
 579 * Returns NULL or the "data" token handed to virtqueue_add_buf().
 580 * This is not valid on an active queue; it is useful only for device
 581 * shutdown.
 582 */
 583void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
 584{
 585        struct vring_virtqueue *vq = to_vvq(_vq);
 586        unsigned int i;
 587        void *buf;
 588
 589        START_USE(vq);
 590
 591        for (i = 0; i < vq->vring.num; i++) {
 592                if (!vq->data[i])
 593                        continue;
 594                /* detach_buf clears data, so grab it now. */
 595                buf = vq->data[i];
 596                detach_buf(vq, i);
 597                vq->vring.avail->idx--;
 598                END_USE(vq);
 599                return buf;
 600        }
 601        /* That should have freed everything. */
 602        BUG_ON(vq->num_free != vq->vring.num);
 603
 604        END_USE(vq);
 605        return NULL;
 606}
 607EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf);
 608
 609irqreturn_t vring_interrupt(int irq, void *_vq)
 610{
 611        struct vring_virtqueue *vq = to_vvq(_vq);
 612
 613        if (!more_used(vq)) {
 614                pr_debug("virtqueue interrupt with no work for %p\n", vq);
 615                return IRQ_NONE;
 616        }
 617
 618        if (unlikely(vq->broken))
 619                return IRQ_HANDLED;
 620
 621        pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
 622        if (vq->vq.callback)
 623                vq->vq.callback(&vq->vq);
 624
 625        return IRQ_HANDLED;
 626}
 627EXPORT_SYMBOL_GPL(vring_interrupt);
 628
 629struct virtqueue *vring_new_virtqueue(unsigned int index,
 630                                      unsigned int num,
 631                                      unsigned int vring_align,
 632                                      struct virtio_device *vdev,
 633                                      bool weak_barriers,
 634                                      void *pages,
 635                                      void (*notify)(struct virtqueue *),
 636                                      void (*callback)(struct virtqueue *),
 637                                      const char *name)
 638{
 639        struct vring_virtqueue *vq;
 640        unsigned int i;
 641
 642        /* We assume num is a power of 2. */
 643        if (num & (num - 1)) {
 644                dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
 645                return NULL;
 646        }
 647
 648        vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL);
 649        if (!vq)
 650                return NULL;
 651
 652        vring_init(&vq->vring, num, pages, vring_align);
 653        vq->vq.callback = callback;
 654        vq->vq.vdev = vdev;
 655        vq->vq.name = name;
 656        vq->notify = notify;
 657        vq->weak_barriers = weak_barriers;
 658        vq->broken = false;
 659        vq->last_used_idx = 0;
 660        vq->num_added = 0;
 661        vq->queue_index = index;
 662        list_add_tail(&vq->vq.list, &vdev->vqs);
 663#ifdef DEBUG
 664        vq->in_use = false;
 665        vq->last_add_time_valid = false;
 666#endif
 667
 668        vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);
 669        vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
 670
 671        /* No callback?  Tell other side not to bother us. */
 672        if (!callback)
 673                vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
 674
 675        /* Put everything in free lists. */
 676        vq->num_free = num;
 677        vq->free_head = 0;
 678        for (i = 0; i < num-1; i++) {
 679                vq->vring.desc[i].next = i+1;
 680                vq->data[i] = NULL;
 681        }
 682        vq->data[i] = NULL;
 683
 684        return &vq->vq;
 685}
 686EXPORT_SYMBOL_GPL(vring_new_virtqueue);
 687
 688void vring_del_virtqueue(struct virtqueue *vq)
 689{
 690        list_del(&vq->list);
 691        kfree(to_vvq(vq));
 692}
 693EXPORT_SYMBOL_GPL(vring_del_virtqueue);
 694
 695/* Manipulates transport-specific feature bits. */
 696void vring_transport_features(struct virtio_device *vdev)
 697{
 698        unsigned int i;
 699
 700        for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
 701                switch (i) {
 702                case VIRTIO_RING_F_INDIRECT_DESC:
 703                        break;
 704                case VIRTIO_RING_F_EVENT_IDX:
 705                        break;
 706                default:
 707                        /* We don't understand this bit. */
 708                        clear_bit(i, vdev->features);
 709                }
 710        }
 711}
 712EXPORT_SYMBOL_GPL(vring_transport_features);
 713
 714/**
 715 * virtqueue_get_vring_size - return the size of the virtqueue's vring
 716 * @vq: the struct virtqueue containing the vring of interest.
 717 *
 718 * Returns the size of the vring.  This is mainly used for boasting to
 719 * userspace.  Unlike other operations, this need not be serialized.
 720 */
 721unsigned int virtqueue_get_vring_size(struct virtqueue *_vq)
 722{
 723
 724        struct vring_virtqueue *vq = to_vvq(_vq);
 725
 726        return vq->vring.num;
 727}
 728EXPORT_SYMBOL_GPL(virtqueue_get_vring_size);
 729
 730MODULE_LICENSE("GPL");
 731
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.