-----Original Message-----
From: Paolo Bonzini [mailto:pbonzini@redhat.com]
Sent: Monday, June 4, 2018 6:03 PM
To: Liu, Changpeng <redacted>; Stefan Hajnoczi
[off-list ref]
Cc: virtualization@lists.linux-foundation.org; cavery@redhat.com;
jasowang@redhat.com; Wang, Wei W [off-list ref]
Subject: Re: [PATCH v4] virtio_blk: add DISCARD and WRIET ZEROES commands
support

On 04/06/2018 06:14, Liu, Changpeng wrote:

quoted

quoted

quoted

But I believe the specification says VIRTIO_BLK_T_OUT means direction, so
OR the two bits together should compliance with the specification.

I cannot find that in the specification:

  http://docs.oasis-open.org/virtio/virtio/v1.0/cs04/virtio-v1.0-cs04.html#x1-
2020002

and it would contradict the "The type of the request is either ... or
..." wording that I quoted from the spec above.

If you do find something in the spec, please let me know and we can
figure out how to make the spec consistent.

I saw comments from file linux/usr/include/uapi/linux/virtio_blk.h, which says
VIRTIO_BLK_T_OUT may be combined with other commands and means direction,
the specification does not have such description.

I don't think it is in the specification indeed (however, 11 and 13 were
chosen so that VIRTIO_BLK_T_OUT can still indicate direction).

Correct, we don't need to OR VIRTIO_BLK_T_OUT again for DISCARD and WRITE ZEROES commands.
I'll remove it in next patch set.

Paolo