On Sat, Jan 07, 2023 at 07:44:37PM +0000, Richard W.M. Jones wrote:
 
 This is upstream in nbdkit now:
 
https://gitlab.com/nbdkit/nbdkit/-/tree/master/plugins/blkio
 
 Another question:
 
 (6) vhost-user + "read-only" property acts a bit strangely.  After
 opening virtio-blk-vhost-user it throws an EROFS error if you try to
 "blkio_start" it.  However if you set the "read-only" property to
true
 then it's OK to start it, and subsequent read operations work too.
 
 I would expect that any device can be started without needing to set
 this property, and in general I don't understand why vhost-user is r/o
 since everything I read about it seems to indicate it's a general
 purpose writable protocol. 
I guess the vhost-user-blk server is read-only and that's why it's
refusing to blkio_start() unless readonly was set to true.
If you're using qemu-storage-daemon, set the writable=on parameter on
the export.
Stefan