qemu

virtio-blk-handler.c (7417B)

---

 /*
  * Handler for virtio-blk I/O
  *
  * Copyright (c) 2020 Red Hat, Inc.
  * Copyright (C) 2022 Bytedance Inc. and/or its affiliates. All rights reserved.
  *
  * Author:
  *   Coiby Xu <coiby.xu@gmail.com>
  *   Xie Yongji <xieyongji@bytedance.com>
  *
  * This work is licensed under the terms of the GNU GPL, version 2 or
  * later.  See the COPYING file in the top-level directory.
  */
 
 #include "qemu/osdep.h"
 #include "qemu/error-report.h"
 #include "virtio-blk-handler.h"
 
 #include "standard-headers/linux/virtio_blk.h"
 
 struct virtio_blk_inhdr {
     unsigned char status;
 };
 
 static bool virtio_blk_sect_range_ok(BlockBackend *blk, uint32_t block_size,
                                      uint64_t sector, size_t size)
 {
     uint64_t nb_sectors;
     uint64_t total_sectors;
 
     if (size % VIRTIO_BLK_SECTOR_SIZE) {
         return false;
     }
 
     nb_sectors = size >> VIRTIO_BLK_SECTOR_BITS;
 
     QEMU_BUILD_BUG_ON(BDRV_SECTOR_SIZE != VIRTIO_BLK_SECTOR_SIZE);
     if (nb_sectors > BDRV_REQUEST_MAX_SECTORS) {
         return false;
     }
     if ((sector << VIRTIO_BLK_SECTOR_BITS) % block_size) {
         return false;
     }
     blk_get_geometry(blk, &total_sectors);
     if (sector > total_sectors || nb_sectors > total_sectors - sector) {
         return false;
     }
     return true;
 }
 
 static int coroutine_fn
 virtio_blk_discard_write_zeroes(VirtioBlkHandler *handler, struct iovec *iov,
                                 uint32_t iovcnt, uint32_t type)
 {
     BlockBackend *blk = handler->blk;
     struct virtio_blk_discard_write_zeroes desc;
     ssize_t size;
     uint64_t sector;
     uint32_t num_sectors;
     uint32_t max_sectors;
     uint32_t flags;
     int bytes;
 
     /* Only one desc is currently supported */
     if (unlikely(iov_size(iov, iovcnt) > sizeof(desc))) {
         return VIRTIO_BLK_S_UNSUPP;
     }
 
     size = iov_to_buf(iov, iovcnt, 0, &desc, sizeof(desc));
     if (unlikely(size != sizeof(desc))) {
         error_report("Invalid size %zd, expected %zu", size, sizeof(desc));
         return VIRTIO_BLK_S_IOERR;
     }
 
     sector = le64_to_cpu(desc.sector);
     num_sectors = le32_to_cpu(desc.num_sectors);
     flags = le32_to_cpu(desc.flags);
     max_sectors = (type == VIRTIO_BLK_T_WRITE_ZEROES) ?
                   VIRTIO_BLK_MAX_WRITE_ZEROES_SECTORS :
                   VIRTIO_BLK_MAX_DISCARD_SECTORS;
 
     /* This check ensures that 'bytes' fits in an int */
     if (unlikely(num_sectors > max_sectors)) {
         return VIRTIO_BLK_S_IOERR;
     }
 
     bytes = num_sectors << VIRTIO_BLK_SECTOR_BITS;
 
     if (unlikely(!virtio_blk_sect_range_ok(blk, handler->logical_block_size,
                                            sector, bytes))) {
         return VIRTIO_BLK_S_IOERR;
     }
 
     /*
      * The device MUST set the status byte to VIRTIO_BLK_S_UNSUPP for discard
      * and write zeroes commands if any unknown flag is set.
      */
     if (unlikely(flags & ~VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP)) {
         return VIRTIO_BLK_S_UNSUPP;
     }
 
     if (type == VIRTIO_BLK_T_WRITE_ZEROES) {
         int blk_flags = 0;
 
         if (flags & VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP) {
             blk_flags |= BDRV_REQ_MAY_UNMAP;
         }
 
         if (blk_co_pwrite_zeroes(blk, sector << VIRTIO_BLK_SECTOR_BITS,
                                  bytes, blk_flags) == 0) {
             return VIRTIO_BLK_S_OK;
         }
     } else if (type == VIRTIO_BLK_T_DISCARD) {
         /*
          * The device MUST set the status byte to VIRTIO_BLK_S_UNSUPP for
          * discard commands if the unmap flag is set.
          */
         if (unlikely(flags & VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP)) {
             return VIRTIO_BLK_S_UNSUPP;
         }
 
         if (blk_co_pdiscard(blk, sector << VIRTIO_BLK_SECTOR_BITS,
                             bytes) == 0) {
             return VIRTIO_BLK_S_OK;
         }
     }
 
     return VIRTIO_BLK_S_IOERR;
 }
 
 int coroutine_fn virtio_blk_process_req(VirtioBlkHandler *handler,
                                         struct iovec *in_iov,
                                         struct iovec *out_iov,
                                         unsigned int in_num,
                                         unsigned int out_num)
 {
     BlockBackend *blk = handler->blk;
     struct virtio_blk_inhdr *in;
     struct virtio_blk_outhdr out;
     uint32_t type;
     int in_len;
 
     if (out_num < 1 || in_num < 1) {
         error_report("virtio-blk request missing headers");
         return -EINVAL;
     }
 
     if (unlikely(iov_to_buf(out_iov, out_num, 0, &out,
                             sizeof(out)) != sizeof(out))) {
         error_report("virtio-blk request outhdr too short");
         return -EINVAL;
     }
 
     iov_discard_front(&out_iov, &out_num, sizeof(out));
 
     if (in_iov[in_num - 1].iov_len < sizeof(struct virtio_blk_inhdr)) {
         error_report("virtio-blk request inhdr too short");
         return -EINVAL;
     }
 
     /* We always touch the last byte, so just see how big in_iov is. */
     in_len = iov_size(in_iov, in_num);
     in = (void *)in_iov[in_num - 1].iov_base
                  + in_iov[in_num - 1].iov_len
                  - sizeof(struct virtio_blk_inhdr);
     iov_discard_back(in_iov, &in_num, sizeof(struct virtio_blk_inhdr));
 
     type = le32_to_cpu(out.type);
     switch (type & ~VIRTIO_BLK_T_BARRIER) {
     case VIRTIO_BLK_T_IN:
     case VIRTIO_BLK_T_OUT: {
         QEMUIOVector qiov;
         int64_t offset;
         ssize_t ret = 0;
         bool is_write = type & VIRTIO_BLK_T_OUT;
         int64_t sector_num = le64_to_cpu(out.sector);
 
         if (is_write && !handler->writable) {
             in->status = VIRTIO_BLK_S_IOERR;
             break;
         }
 
         if (is_write) {
             qemu_iovec_init_external(&qiov, out_iov, out_num);
         } else {
             qemu_iovec_init_external(&qiov, in_iov, in_num);
         }
 
         if (unlikely(!virtio_blk_sect_range_ok(blk,
                                                handler->logical_block_size,
                                                sector_num, qiov.size))) {
             in->status = VIRTIO_BLK_S_IOERR;
             break;
         }
 
         offset = sector_num << VIRTIO_BLK_SECTOR_BITS;
 
         if (is_write) {
             ret = blk_co_pwritev(blk, offset, qiov.size, &qiov, 0);
         } else {
             ret = blk_co_preadv(blk, offset, qiov.size, &qiov, 0);
         }
         if (ret >= 0) {
             in->status = VIRTIO_BLK_S_OK;
         } else {
             in->status = VIRTIO_BLK_S_IOERR;
         }
         break;
     }
     case VIRTIO_BLK_T_FLUSH:
         if (blk_co_flush(blk) == 0) {
             in->status = VIRTIO_BLK_S_OK;
         } else {
             in->status = VIRTIO_BLK_S_IOERR;
         }
         break;
     case VIRTIO_BLK_T_GET_ID: {
         size_t size = MIN(strlen(handler->serial) + 1,
                           MIN(iov_size(in_iov, in_num),
                               VIRTIO_BLK_ID_BYTES));
         iov_from_buf(in_iov, in_num, 0, handler->serial, size);
         in->status = VIRTIO_BLK_S_OK;
         break;
     }
     case VIRTIO_BLK_T_DISCARD:
     case VIRTIO_BLK_T_WRITE_ZEROES:
         if (!handler->writable) {
             in->status = VIRTIO_BLK_S_IOERR;
             break;
         }
         in->status = virtio_blk_discard_write_zeroes(handler, out_iov,
                                                      out_num, type);
         break;
     default:
         in->status = VIRTIO_BLK_S_UNSUPP;
         break;
     }
 
     return in_len;
 }