int virtio_blk_handle_scsi_req(VirtIOBlock *blk, VirtQueueElement *elem) { int status = VIRTIO_BLK_S_OK; struct virtio_scsi_inhdr *scsi = NULL; VirtIODevice *vdev = VIRTIO_DEVICE(blk); #ifdef __linux__ int i; struct sg_io_hdr hdr; #endif /* * We require at least one output segment each for the virtio_blk_outhdr * and the SCSI command block. * * We also at least require the virtio_blk_inhdr, the virtio_scsi_inhdr * and the sense buffer pointer in the input segments. */ if (elem->out_num < 2 || elem->in_num < 3) { status = VIRTIO_BLK_S_IOERR; goto fail; } /* * The scsi inhdr is placed in the second-to-last input segment, just * before the regular inhdr. */ scsi = (void *)elem->in_sg[elem->in_num - 2].iov_base; if (!blk->conf.scsi) { status = VIRTIO_BLK_S_UNSUPP; goto fail; } /* * No support for bidirection commands yet. */ if (elem->out_num > 2 && elem->in_num > 3) { status = VIRTIO_BLK_S_UNSUPP; goto fail; } #ifdef __linux__ memset(&hdr, 0, sizeof(struct sg_io_hdr)); hdr.interface_id = 'S'; hdr.cmd_len = elem->out_sg[1].iov_len; hdr.cmdp = elem->out_sg[1].iov_base; hdr.dxfer_len = 0; if (elem->out_num > 2) { /* * If there are more than the minimally required 2 output segments * there is write payload starting from the third iovec. */ hdr.dxfer_direction = SG_DXFER_TO_DEV; hdr.iovec_count = elem->out_num - 2; for (i = 0; i < hdr.iovec_count; i++) hdr.dxfer_len += elem->out_sg[i + 2].iov_len; hdr.dxferp = elem->out_sg + 2; } else if (elem->in_num > 3) { /* * If we have more than 3 input segments the guest wants to actually * read data. */ hdr.dxfer_direction = SG_DXFER_FROM_DEV; hdr.iovec_count = elem->in_num - 3; for (i = 0; i < hdr.iovec_count; i++) hdr.dxfer_len += elem->in_sg[i].iov_len; hdr.dxferp = elem->in_sg; } else { /* * Some SCSI commands don't actually transfer any data. */ hdr.dxfer_direction = SG_DXFER_NONE; } hdr.sbp = elem->in_sg[elem->in_num - 3].iov_base; hdr.mx_sb_len = elem->in_sg[elem->in_num - 3].iov_len; status = bdrv_ioctl(blk->bs, SG_IO, &hdr); if (status) { status = VIRTIO_BLK_S_UNSUPP; goto fail; } /* * From SCSI-Generic-HOWTO: "Some lower level drivers (e.g. ide-scsi) * clear the masked_status field [hence status gets cleared too, see * block/scsi_ioctl.c] even when a CHECK_CONDITION or COMMAND_TERMINATED * status has occurred. However they do set DRIVER_SENSE in driver_status * field. Also a (sb_len_wr > 0) indicates there is a sense buffer. */ if (hdr.status == 0 && hdr.sb_len_wr > 0) { hdr.status = CHECK_CONDITION; } virtio_stl_p(vdev, &scsi->errors, hdr.status | (hdr.msg_status << 8) | (hdr.host_status << 16) | (hdr.driver_status << 24)); virtio_stl_p(vdev, &scsi->residual, hdr.resid); virtio_stl_p(vdev, &scsi->sense_len, hdr.sb_len_wr); virtio_stl_p(vdev, &scsi->data_len, hdr.dxfer_len); return status; #else abort(); #endif fail: /* Just put anything nonzero so that the ioctl fails in the guest. */ if (scsi) { virtio_stl_p(vdev, &scsi->errors, 255); } return status; }