Pass the sense reason as an explicit return value from the I/O submission
path instead of storing it in struct se_cmd and using negative return
values.  This cleans up a lot of the code pathes, and with the sparse
annotations for the new sense_reason_t type allows for much better
error checking.

(nab: Convert spc_emulate_modesense + spc_emulate_modeselect to use
      sense_reason_t with Roland's MODE SELECT changes)
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Cc: Roland Dreier <roland@purestorage.com>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

This patch converts tcm_vhost to use target_submit_cmd_map_sgls() for
I/O submission and mapping of pre-allocated SGL memory from incoming
virtio-scsi SGL memory -> se_cmd descriptors.

This includes removing the original open-coded fabric uses of target
core callers to support transport_generic_map_mem_to_cmd() between
target_setup_cmd_from_cdb() and transport_handle_cdb_direct() logic.

It also includes adding a handful of new tcm_vhost_cmnd member +
assignments in vhost_scsi_allocate_cmd() used from cmwq process
context I/O submission within tcm_vhost_submission_work()

(v2: Use renamed target_submit_cmd_map_sgls)
Reported-by: NChristoph Hellwig <hch@lst.de>
Cc: Christoph Hellwig <hch@lst.de>
Acked-by: NMichael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

Every fabric driver has to supply a se_tfo->set_fabric_sense_len()
method, just so iSCSI can return an offset of 2.  However, every fabric
driver is already allocating a sense buffer and passing it into the
target core, either via transport_init_se_cmd() or target_submit_cmd().

So instead of having iSCSI pass the start of its sense buffer into the
core and then later tell the core to skip the first 2 bytes, it seems
easier for iSCSI just to do the offset of 2 when it passes the sense
buffer into the core.  Then we can drop the se_tfo->set_fabric_sense_len()
everywhere, and just add a couple of lines of code to iSCSI to set the
sense data length to the beginning of the buffer right before it sends
it over the network.

(nab: Remove .set_fabric_sense_len usage from tcm_qla2xxx_npiv_ops +
      change transport_get_sense_buffer to follow v3.6-rc6 code w/o
      ->set_fabric_sense_len usage)
Signed-off-by: NRoland Dreier <roland@purestorage.com>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

There are no callers of se_tfo->get_fabric_sense_len(), so we should
stop having every fabric driver implement it.
Signed-off-by: NRoland Dreier <roland@purestorage.com>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

Here TRANSPORT_IQN_LEN is 224, which is a multiple of 4.
Since vhost_tpgt is 2 bytes and abi_version is 4, the total size would
be 230.  But gcc needs struct size be aligned to first field size, which
is 4 bytes, so it pads the structure by extra 2 bytes to the total of
232.

This padding is very undesirable in an ABI:
- it can not be initialized easily
- it can not be checked easily
- it can leak information between kernel and userspace

Simplest solution is probably just to make the padding
explicit.

(v2: Add check for zero'ed backend->reserved field for VHOST_SCSI_SET_ENDPOINT
     and VHOST_SCSI_CLEAR_ENDPOINT ops as requested by MST)
Reported-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

This patch contains the post RFC-v5 (post-merge) changes, this includes:

- Add locking comment
- Move vhost_scsi_complete_cmd ahead of TFO callbacks in order to
  drop forward declarations
- Drop extra '!= NULL' usage in vhost_scsi_complete_cmd_work()
- Change vhost_scsi_*_handle_kick() to use pr_debug
- Fix possible race in vhost_scsi_set_endpoint() for vs->vs_tpg checking
  + assignment.
- Convert tv_tpg->tpg_vhost_count + ->tv_tpg_port_count from atomic_t ->
  int, and make sure reference is protected by ->tv_tpg_mutex.
- Drop unnecessary vhost_scsi->vhost_ref_cnt
- Add 'err:' label for exception path in vhost_scsi_clear_endpoint()
- Add enum for VQ numbers, add usage in vhost_scsi_open()
- Add vhost_scsi_flush() + vhost_scsi_flush_vq() following
  drivers/vhost/net.c
- Add smp_wmb() + vhost_scsi_flush() call during vhost_scsi_set_features()
- Drop unnecessary copy_from_user() usage with GET_ABI_VERSION ioctl
- Add missing vhost_scsi_compat_ioctl() caller for vhost_scsi_fops
- Fix function parameter definition first line to follow existing
  vhost code style
- Change 'vHost' usage -> 'vhost' in handful of locations
- Change -EPERM -> -EBUSY usage for two failures in tcm_vhost_drop_nexus()
- Add comment for tcm_vhost_workqueue in tcm_vhost_init()
- Make GET_ABI_VERSION return 'int' + add comment in tcm_vhost.h
Reported-by: NMichael S. Tsirkin <mst@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>
Cc: Zhi Yong Wu <wuzhy@cn.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

Fix up a new coccinelle warnings reported by Fengguang Wu + Intel
0-DAY kernel build testing backend:

drivers/vhost/tcm_vhost.c:537:23-29: ERROR: allocation function on line
533 returns NULL not ERR_PTR on failure

vim +537 drivers/vhost/tcm_vhost.c
   534          if (!sg)
   535                  return -ENOMEM;
   536          pr_debug("%s sg %p sgl_count %u is_err %ld\n", __func__,
 > 537                 sg, sgl_count, IS_ERR(sg));
   538          sg_init_table(sg, sgl_count);
   539
   540          tv_cmd->tvc_sgl = sg;
Signed-off-by: NFengguang Wu <fengguang.wu@intel.com>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

This patch adds the initial code for tcm_vhost, a Vhost level TCM
fabric driver for virtio SCSI initiators into KVM guest.

This code is currently up and running on v3.5-rc2 host+guest
from target-pending/for-next-merge.

Using tcm_vhost requires Zhi's -> Stefan -> nab's qemu vhost-scsi tree here:

  http://git.kernel.org/?p=virt/kvm/nab/qemu-kvm.git;a=shortlog;h=refs/heads/vhost-scsi

--

Changelog v4 -> v5:

  Expose ABI version via VHOST_SCSI_GET_ABI_VERSION + use Rev 0 as
  starting point for v3.6-rc code (Stefan + ALiguori + nab)
  Convert vhost_scsi_handle_vq() to vq_err() (nab + MST)
  Minor style fixes from checkpatch (nab)

Changelog v3 -> v4:

  Rename vhost_vring_target -> vhost_scsi_target (mst + nab)
  Use TRANSPORT_IQN_LEN in vhost_scsi_target->vhost_wwpn[] def (nab)
  Move back to drivers/vhost/, and just use drivers/vhost/Kconfig.tcm (mst)
  Move TCM_VHOST related ioctl defines from include/linux/vhost.h ->
  drivers/vhost/tcm_vhost.h as requested by MST (nab)
  Move Kbuild.tcm include from drivers/staging -> drivers/vhost/, and
  just use 'if STAGING' around 'source drivers/vhost/Kbuild.tcm'

Changelog v2 -> v3:

  Unlock on error in tcm_vhost_drop_nexus() (DanC)
  Fix strlen() doesn't count the terminator (DanC)
  Call kfree() on an error path (DanC)
  Convert tcm_vhost_write_pending to use target_execute_cmd (hch + nab)
  Fix another strlen() off by one in tcm_vhost_make_tport (DanC)
  Add option under drivers/staging/Kconfig, and move to drivers/vhost/tcm/
  as requested by MST (nab)

Changelog v1 -> v2:

  Fix tv_cmd completion -> release SGL memory leak (nab)
  Fix sparse warnings for static variable usage ((Fengguang Wu)
  Fix sparse warnings for min() typing + printk format specs (Fengguang Wu)
  Convert to cmwq submission for I/O dispatch (nab + hch)

Changelog v0 -> v1:

  Merge into single source + header file, and move to drivers/vhost/
Acked-by: NMichael S. Tsirkin <mst@redhat.com>
Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>
Cc: Zhi Yong Wu <wuzhy@cn.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>