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ISCSI: Add SCSI passthrough via scsi-generic to libiscsi
Update iscsi to allow passthrough of SG_IO scsi commands when the iscsi
device is forced to be scsi-generic.
Implement both bdrv_ioctl() and bdrv_aio_ioctl() in the iscsi backend,
emulate the SG_IO ioctl and pass the SCSI commands across to the
iscsi target.
This allows end-to-end passthrough of SCSI all the way from the guest,
to qemu, via scsi-generic, then libiscsi all the way to the iscsi target.
To activate this you need to specify that the iscsi lun should be treated
as a scsi-generic device.
Example:
-device lsi -device scsi-generic,drive=MyISCSI \
-drive file=iscsi://10.1.1.125/iqn.ronnie.test/1,if=none,id=MyISCSI
Note, you can currently not boot a qemu guest from a scsi device.
Note,
This only works when the host is linux, since the emulation relies on
definitions of SG_IO from the scsi-generic implementation in the
linux kernel.
It should be fairly easy to re-implement some structures similar enough
for non-linux hosts to do the same style of passthrough via a fake
scsi generic layer and libiscsi if need be.
Signed-off-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Ronnie Sahlberg
Paolo Bonzini
parent
1a4f0c3a06
commit
983924532f
142
block/iscsi.c
142
block/iscsi.c
@ -35,6 +35,10 @@
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#include <iscsi/iscsi.h>
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#include <iscsi/scsi-lowlevel.h>
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#ifdef __linux__
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#include <scsi/sg.h>
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#include <hw/scsi-defs.h>
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#endif
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typedef struct IscsiLun {
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struct iscsi_context *iscsi;
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@ -56,6 +60,9 @@ typedef struct IscsiAIOCB {
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int canceled;
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size_t read_size;
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size_t read_offset;
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#ifdef __linux__
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sg_io_hdr_t *ioh;
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#endif
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} IscsiAIOCB;
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struct IscsiTask {
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@ -515,6 +522,136 @@ iscsi_aio_discard(BlockDriverState *bs,
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return &acb->common;
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}
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#ifdef __linux__
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static void
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iscsi_aio_ioctl_cb(struct iscsi_context *iscsi, int status,
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void *command_data, void *opaque)
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{
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IscsiAIOCB *acb = opaque;
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if (acb->canceled != 0) {
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qemu_aio_release(acb);
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scsi_free_scsi_task(acb->task);
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acb->task = NULL;
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return;
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}
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acb->status = 0;
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if (status < 0) {
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error_report("Failed to ioctl(SG_IO) to iSCSI lun. %s",
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iscsi_get_error(iscsi));
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acb->status = -EIO;
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}
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acb->ioh->driver_status = 0;
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acb->ioh->host_status = 0;
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acb->ioh->resid = 0;
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#define SG_ERR_DRIVER_SENSE 0x08
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if (status == SCSI_STATUS_CHECK_CONDITION && acb->task->datain.size >= 2) {
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int ss;
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acb->ioh->driver_status |= SG_ERR_DRIVER_SENSE;
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acb->ioh->sb_len_wr = acb->task->datain.size - 2;
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ss = (acb->ioh->mx_sb_len >= acb->ioh->sb_len_wr) ?
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acb->ioh->mx_sb_len : acb->ioh->sb_len_wr;
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memcpy(acb->ioh->sbp, &acb->task->datain.data[2], ss);
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}
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iscsi_schedule_bh(iscsi_readv_writev_bh_cb, acb);
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scsi_free_scsi_task(acb->task);
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acb->task = NULL;
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}
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static BlockDriverAIOCB *iscsi_aio_ioctl(BlockDriverState *bs,
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unsigned long int req, void *buf,
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BlockDriverCompletionFunc *cb, void *opaque)
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{
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IscsiLun *iscsilun = bs->opaque;
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struct iscsi_context *iscsi = iscsilun->iscsi;
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struct iscsi_data data;
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IscsiAIOCB *acb;
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assert(req == SG_IO);
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acb = qemu_aio_get(&iscsi_aio_pool, bs, cb, opaque);
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acb->iscsilun = iscsilun;
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acb->canceled = 0;
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acb->buf = NULL;
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acb->ioh = buf;
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acb->task = malloc(sizeof(struct scsi_task));
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if (acb->task == NULL) {
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error_report("iSCSI: Failed to allocate task for scsi command. %s",
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iscsi_get_error(iscsi));
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qemu_aio_release(acb);
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return NULL;
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}
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memset(acb->task, 0, sizeof(struct scsi_task));
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switch (acb->ioh->dxfer_direction) {
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case SG_DXFER_TO_DEV:
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acb->task->xfer_dir = SCSI_XFER_WRITE;
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break;
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case SG_DXFER_FROM_DEV:
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acb->task->xfer_dir = SCSI_XFER_READ;
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break;
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default:
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acb->task->xfer_dir = SCSI_XFER_NONE;
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break;
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}
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acb->task->cdb_size = acb->ioh->cmd_len;
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memcpy(&acb->task->cdb[0], acb->ioh->cmdp, acb->ioh->cmd_len);
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acb->task->expxferlen = acb->ioh->dxfer_len;
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if (acb->task->xfer_dir == SCSI_XFER_WRITE) {
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data.data = acb->ioh->dxferp;
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data.size = acb->ioh->dxfer_len;
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}
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if (iscsi_scsi_command_async(iscsi, iscsilun->lun, acb->task,
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iscsi_aio_ioctl_cb,
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(acb->task->xfer_dir == SCSI_XFER_WRITE) ?
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&data : NULL,
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acb) != 0) {
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scsi_free_scsi_task(acb->task);
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qemu_aio_release(acb);
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return NULL;
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}
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/* tell libiscsi to read straight into the buffer we got from ioctl */
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if (acb->task->xfer_dir == SCSI_XFER_READ) {
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scsi_task_add_data_in_buffer(acb->task,
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acb->ioh->dxfer_len,
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acb->ioh->dxferp);
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}
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iscsi_set_events(iscsilun);
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return &acb->common;
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}
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static int iscsi_ioctl(BlockDriverState *bs, unsigned long int req, void *buf)
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{
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IscsiLun *iscsilun = bs->opaque;
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switch (req) {
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case SG_GET_VERSION_NUM:
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*(int *)buf = 30000;
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break;
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case SG_GET_SCSI_ID:
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((struct sg_scsi_id *)buf)->scsi_type = iscsilun->type;
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break;
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default:
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return -1;
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}
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return 0;
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}
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#endif
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static int64_t
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iscsi_getlength(BlockDriverState *bs)
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{
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@ -926,6 +1063,11 @@ static BlockDriver bdrv_iscsi = {
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.bdrv_aio_flush = iscsi_aio_flush,
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.bdrv_aio_discard = iscsi_aio_discard,
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#ifdef __linux__
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.bdrv_ioctl = iscsi_ioctl,
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.bdrv_aio_ioctl = iscsi_aio_ioctl,
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#endif
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};
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static void iscsi_block_init(void)
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@ -400,12 +400,6 @@ static int scsi_generic_initfn(SCSIDevice *s)
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return -1;
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}
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/* check we are really using a /dev/sg* file */
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if (!bdrv_is_sg(s->conf.bs)) {
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error_report("not /dev/sg*");
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return -1;
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}
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if (bdrv_get_on_error(s->conf.bs, 0) != BLOCK_ERR_STOP_ENOSPC) {
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error_report("Device doesn't support drive option werror");
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return -1;
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@ -416,8 +410,11 @@ static int scsi_generic_initfn(SCSIDevice *s)
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}
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/* check we are using a driver managing SG_IO (version 3 and after */
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if (bdrv_ioctl(s->conf.bs, SG_GET_VERSION_NUM, &sg_version) < 0 ||
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sg_version < 30000) {
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if (bdrv_ioctl(s->conf.bs, SG_GET_VERSION_NUM, &sg_version) < 0) {
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error_report("scsi generic interface not supported");
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return -1;
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}
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if (sg_version < 30000) {
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error_report("scsi generic interface too old");
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return -1;
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}
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