[PATCH] virtio-spec: add field for scsi command size

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

Add field for guest to specify command size for virtio-blk.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 virtio-spec.lyx | 83 +++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 78 insertions(+), 5 deletions(-)

diff --git a/virtio-spec.lyx b/virtio-spec.lyx
index a8ce3f9..fea97ed 100644
--- a/virtio-spec.lyx
+++ b/virtio-spec.lyx
@@ -5826,6 +5826,16 @@ VIRTIO_BLK_F_TOPOLOGY (10) Device exports information on optimal I/O alignment.
 \change_inserted 1531152142 1341302349
 VIRTIO_BLK_F_CONFIG_WCE (11) Device can toggle its cache between writeback
  and writethrough modes.
+\change_inserted 1986246365 1363257418
+
+\end_layout
+
+\begin_layout Description
+
+\change_inserted 1986246365 1363258629
+VIRTIO_BLK_F_CMD_SIZE (12) cmd_size field is valid.
+\change_inserted 1531152142 1341302349
+
 \end_layout
 
 \end_deeper
@@ -5994,6 +6004,30 @@ struct virtio_blk_config {
 \change_inserted 1531152142 1341301918
 
     u8 writeback;
+\change_inserted 1986246365 1363257385
+
+\end_layout
+
+\begin_layout Plain Layout
+
+\change_inserted 1986246365 1363258610
+
+    u8 reserved[3];
+\end_layout
+
+\begin_layout Plain Layout
+
+\change_inserted 1986246365 1363259147
+
+    // buffer length for cmd field in requests.
+ reset value 0.
+\end_layout
+
+\begin_layout Plain Layout
+
+\change_inserted 1986246365 1363257810
+
+    u32 cmd_size;
 \change_unchanged
 
 \end_layout
@@ -6085,6 +6119,21 @@ Until version 1.1, QEMU remained in writeback mode even after a guest announced
 \end_inset
 
 .
+\change_inserted 1986246365 1363258989
+
+\end_layout
+
+\begin_layout Enumerate
+
+\change_inserted 1986246365 1363259237
+If VIRTIO_BLK_F_SCSI_CMD_SIZE is negotiated, Guest should set the desired
+ size for scsi commands to the 
+\emph on
+cmd_size 
+\emph default
+field.
+\change_unchanged
+
 \end_layout
 
 \begin_layout Section*
@@ -6369,8 +6418,33 @@ cmd
 \emph default
  field is only present for scsi packet command requests, and indicates the
  command to perform.
- This field must reside in a single, separate read-only buffer; command
- length can be derived from the length of this buffer.
+ 
+\change_inserted 1986246365 1363258881
+If VIRTIO_BLK_F_SCSI_CMD_SIZE feature bit is negotiated, Guest must set
+ the command length by writing it to the cmd_size field in configuration
+ space
+\begin_inset Foot
+status open
+
+\begin_layout Plain Layout
+
+\change_inserted 1986246365 1363258931
+Guest should always set cmd_size during initialization.
+\change_unchanged
+
+\end_layout
+
+\end_inset
+
+.
+ If VIRTIO_BLK_F_SCSI_CMD_SIZE is not negotiated, 
+\change_deleted 1986246365 1363258703
+T
+\change_inserted 1986246365 1363258703
+t
+\change_unchanged
+his field must reside in a single, separate read-only buffer; command length
+ can be derived from the length of this buffer.
  
 \end_layout
 
-- 
MST