scsi: vhost: Notify TCM about the maximum sg entries supported per command

BugLink: https://bugs.launchpad.net/bugs/1885322
[ Upstream commit 5ae6a6a915033bfee79e76e0c374d4f927909edc ]

vhost-scsi pre-allocates the maximum sg entries per command and if a
command requires more than VHOST_SCSI_PREALLOC_SGLS entries, then that
command is failed by it. This patch lets vhost communicate the max sg limit
when it registers vhost_scsi_ops with TCM. With this change, TCM would
report the max sg entries through "Block Limits" VPD page which will be
typically queried by the SCSI initiator during device discovery. By knowing
this limit, the initiator could ensure the maximum transfer length is less
than or equal to what is reported by vhost-scsi.

Link: https://lore.kernel.org/r/1590166317-953-1-git-send-email-sudhakar.panneerselvam@oracle.com
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Sudhakar Panneerselvam <sudhakar.panneerselvam@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index a9caf1bc3c3ef29542530f379d8cc13bd273f30f..88ce114790d75fff9a04dec0a0f4d5bf90dd5606 100644 (file)
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -2290,6 +2290,7 @@ static struct configfs_attribute *vhost_scsi_wwn_attrs[] = {
 static const struct target_core_fabric_ops vhost_scsi_ops = {
        .module                         = THIS_MODULE,
        .fabric_name                    = "vhost",
+       .max_data_sg_nents              = VHOST_SCSI_PREALLOC_SGLS,
        .tpg_get_wwn                    = vhost_scsi_get_fabric_wwn,
        .tpg_get_tag                    = vhost_scsi_get_tpgt,
        .tpg_check_demo_mode            = vhost_scsi_check_true,