[PATCH 0/4] virtio-blk clarifications

On Fri, Aug 17, 2018 at 07:04:42PM +0200, Paolo Bonzini wrote:
> Define them in terms of descriptors, not segments, and explain what the
> driver and device are to use them for. >
> Signed-off-by: Paolo Bonzini <> > ---
>  content.tex
17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-) >
> diff --git a/content.tex b/content.tex
> index 4cdfeef..fd3a3c2 100644 > --- a/content.tex > +++ b/content.tex > @@ -3515,11 +3515,11 @@ device except where noted.
>  subsection{Feature bits}label{sec:Device Types / Block Device / Feature bits} >
>  egin{description} > -item[VIRTIO_BLK_F_SIZE_MAX (1)] Maximum size of any single segment is > -
in field{size_max}. > +item[VIRTIO_BLK_F_SIZE_MAX (1)] Maximum size of any single descriptor in > +
the data portion of a request ("segment") is in field{size_max}. >
> -item[VIRTIO_BLK_F_SEG_MAX (2)] Maximum number of segments in a > -
request is in field{seg_max}. > +item[VIRTIO_BLK_F_SEG_MAX (2)] Maximum number of descriptors in the > +
data portion of a request ("segments") is in field{seg_max}. >
>  item[VIRTIO_BLK_F_GEOMETRY (4)] Disk-style geometry specified in
>
field{geometry}. > @@ -3762,6 +3762,10 @@ error or VIRTIO_BLK_S_UNSUPP for a request unsupported by device:
>  A driver SHOULD NOT submit a request which would cause a read or write
>  beyond field{capacity}. >
> +A driver SHOULD NOT submit a request which has more than field{seg_max} > +descriptors in the data portion, or which has more than field{size_max} > +bytes in a single descriptor in the data portion. > +
>  A driver SHOULD accept the VIRTIO_BLK_F_RO feature if offered. >
>  A driver MUST set field{sector} to 0 for a VIRTIO_BLK_T_FLUSH request. > @@ -3782,6 +3786,11 @@ a range of sectors has been discarded.
>  A device MUST set the field{status} byte to VIRTIO_BLK_S_IOERR for a
>  request which would cause a read or write beyond field{capacity}. >
> +A device MAY set the field{status} byte to VIRTIO_BLK_S_IOERR for a > +request  Well device can always do this for any request, right? I think the distinction is that it can do this for all such requests?
> which has more than field{seg_max} descriptors in the data > +portion, or which has more than field{size_max} bytes in a single > +descriptor in the data portion. > +  Since it's SHOULD NOT for driver, I think another assumption is that device must handle such huge requests anyway then? Do all host implementations actually satisfy this requirement?
>  A device MUST set the field{status} byte to VIRTIO_BLK_S_IOERR
>  for a write request if the VIRTIO_BLK_F_RO feature if offered, and MUST NOT
>  write any data. > --
> 2.17.1 >  >  >  >

---------------------------------------------------------------------
> To unsubscribe from this mail list, you must leave the OASIS TC that
> generates this mail.  Follow this link to all your TCs in OASIS at:
>  https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php