Re: [PATCH-v3 0/9] vhost/scsi: Add ANY_LAYOUT + VERSION_1 support

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Feb 03, 2015 at 06:29:54AM +0000, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <nab@linux-iscsi.org>
> 
> Hi MST, Paolo, Al & Co,
> 
> Here is -v3 for adding vhost/scsi ANY_LAYOUT + VERSION_1 host feature
> bit support.
> 
> It adds a new vhost_virtqueue ->handle_kick() callback to determine the
> start of protection and data payloads iovecs past starting virtio-scsi
> request and response headers, based upon data_direction using iov_iter
> primitives.
> 
> It assumes request/CDB and response/sense_buffer headers may span more
> than a single iovec using mm/iov_iter.c logic.
> 
> It also allows virtio-scsi headers + T10_PI + Data SGL payloads to span
> the same iovec when pinning user-space memory via get_user_pages_fast()
> code.  (Not tested yet)
> 
> Based upon Al & HCH's feedback, the patch series has been converted to
> use copy_*_iter() for virtio-scsi header copy.  Also, patch #4 has been
> updated to use iov_iter_npages() for sgl_count, and patch #5 updated to
> use iov_iter_advance() for calculating prot_bytes offset to the start
> of data_iter.
> 
> v3 changelog:
>   - Convert memcpy_toiovecend -> copy_to_iter usage
>   - Update vhost_scsi_mapal + friends to use iov_iter
>   - Move iov_iter sanity checks into vhost_scsi_calc_sgls
>   - Convert vhost_scsi_calc_sgls() to iov_iter_npages()
>   - Convert to vhost_scsi_handle_vqal to copy_from_iter usage
>   - Update vhost_scsi_handle_vqal comments for iov_iter usage
>   - Convert prot_bytes offset to use iov_iter_advance
>   - Drop max_niov usage in vhost_scsi_handle_vqal
>   - Drop vhost_skip_iovec_bytes in favour of iov_iter
> 
> Note the one part that has been left unchanged is vhost_scsi_map_to_sgl()
> into get_user_pages_fast(), for which existing iov_iter_get_pages() code
> will need to allow for a callback to perform the associated scatterlists
> setup from **pages for protection + data payloads.

I'm not sure it has to be a callback: maybe just add
struct scatterlist *sg parameter and use it if set.

> It's functioning against v3.19-rc1 virtio-scsi LLD in T10_PI mode using
> TYPE-1 DIF with ANY_LAYOUT -> VERSION_1 guest feature bits enabled, using
> the layout following existing convention with protection/data SGL payloads
> residing within seperate iovecs.
> 
> Also included in patch #9 is an over-due change to rename code in scsi.c
> to line up with modern vhost_scsi naming convention.
> 
> Please review.
> 
> Thank you,
> 
> Nicholas Bellinger (9):
>   vhost/scsi: Convert completion path to use copy_to_iser
>   vhost/scsi: Fix incorrect early vhost_scsi_handle_vq failures
>   vhost/scsi: Change vhost_scsi_map_to_sgl to accept iov ptr + len
>   vhost/scsi: Add ANY_LAYOUT iov -> sgl mapping prerequisites
>   vhost/scsi: Add ANY_LAYOUT vhost_virtqueue callback
>   vhost/scsi: Set VIRTIO_F_ANY_LAYOUT + VIRTIO_F_VERSION_1 feature bits
>   vhost/scsi: Drop legacy pre virtio v1.0 !ANY_LAYOUT logic
>   vhost/scsi: Drop left-over scsi_tcq.h include
>   vhost/scsi: Global tcm_vhost -> vhost_scsi rename
> 
>  drivers/vhost/scsi.c | 1073 ++++++++++++++++++++++++++------------------------
>  1 file changed, 549 insertions(+), 524 deletions(-)
> 
> -- 
> 1.9.1