Re: [virtio] [OASIS Issue Tracker] Created: (VIRTIO-20) block: remove ioprio field

[Rusty Russell <rusty@au1.ibm.com>]

OASIS Issues Tracker <workgroup_mailer@lists.oasis-open.org> writes:

> block: remove ioprio field
> --------------------------
>
>                  Key: VIRTIO-20
>                  URL: http://tools.oasis-open.org/issues/browse/VIRTIO-20
>              Project: OASIS Virtual I/O Device (VIRTIO) TC
>           Issue Type: Improvement
>             Reporter: Rusty Russell
>
>
> Did anyone ever actually use it?  We could add it again with a feature when someone does...

commit 7bc092262d787a20e6b09d1cb3a659cf1f37a1d2
Author: Rusty Russell <rusty@au1.ibm.com>
Date:   Wed Sep 11 13:33:46 2013 +0930

    2.4.2.5: Remove ioprio field.
    
    Leave a reserved field in there for alignment.
    
    See: https://tools.oasis-open.org/issues/browse/VIRTIO-20
    
    Signed-off-by: Rusty Russell <rusty@au1.ibm.com>

diff --git a/virtio-v1.0-wd01-part1-specification.txt b/virtio-v1.0-wd01-part1-specification.txt
index 6ab1feb..f82b5f6 100644
--- a/virtio-v1.0-wd01-part1-specification.txt
+++ b/virtio-v1.0-wd01-part1-specification.txt
@@ -1659,7 +1659,7 @@ the device (not necessarily in order). Each request is of form:
 
 	struct virtio_blk_req {
 		u32 type;
-		u32 ioprio;
+		u32 reserved;
 		u64 sector;
 		char data[][512];
 		u8 status;
@@ -1682,10 +1682,6 @@ flush the host cache.
 	#define VIRTIO_BLK_T_FLUSH_OUT    5
 	#define VIRTIO_BLK_T_BARRIER	 0x80000000
 
-The ioprio field is a hint about the relative priorities of
-requests to the device: higher numbers indicate more important
-requests.
-
 The sector number indicates the offset (multiplied by 512) where
 the read or write is to occur. This field is unused and set to 0
 for scsi packet commands and for flush commands.
@@ -1700,6 +1696,10 @@ error or VIRTIO_BLK_S_UNSUPP for a request unsupported by host:
 
 2.4.2.5.1 Legacy Interface: Device Operation
 ------------------------
+The 'reserved' field was previously called ioprio.  The ioprio field
+is a hint about the relative priorities of requests to the device:
+higher numbers indicate more important requests.
+
 Historically, devices assumed that the fields type, ioprio and sector
 reside in a single, separate read-only buffer and the status field is
 a separate read-only buffer of size 1 byte, by itself.