> -----Original Message----- > From: Stefan Hajnoczi [mailto:stefanha@xxxxxxxxxx] > Sent: Thursday, May 31, 2018 6:31 PM > To: Liu, Changpeng <changpeng.liu@xxxxxxxxx> > Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx; cavery@xxxxxxxxxx; > jasowang@xxxxxxxxxx; pbonzini@xxxxxxxxxx; Wang, Wei W > <wei.w.wang@xxxxxxxxx> > Subject: Re: [PATCH v4] virtio_blk: add DISCARD and WRIET ZEROES commands > support > > On Tue, May 29, 2018 at 09:42:24AM +0800, Changpeng Liu wrote: > > num = blk_rq_map_sg(hctx->queue, req, vbr->sg); > > if (num) { > > - if (rq_data_dir(req) == WRITE) > > + if (rq_data_dir(req) == WRITE || type == VIRTIO_BLK_T_DISCARD > || > > + type == VIRTIO_BLK_T_WRITE_ZEROES) > > vbr->out_hdr.type |= cpu_to_virtio32(vblk->vdev, > VIRTIO_BLK_T_OUT); > > The VIRTIO specification says: > > The type of the request is either a read (VIRTIO_BLK_T_IN), a write > (VIRTIO_BLK_T_OUT), a discard (VIRTIO_BLK_T_DISCARD), a write zeroes > (VIRTIO_BLK_T_WRITE_ZEROES) or a flush (VIRTIO_BLK_T_FLUSH). > > But this patch actually uses VIRTIO_BLK_T_DISCARD | VIRTIO_BLK_T_OUT or > VIRTIO_BLK_T_WRITE_ZEROES | VIRTIO_BLK_T_OUT. "either A or B" is > exclusive, it does not mean "A and B". Hi Stefan, For the new add DISCARD and WRITE ZEROES commands, I defined the type code to 11 and 13, so the last bit always is 1, there is no difference in practice. But I believe the specification says VIRTIO_BLK_T_OUT means direction, so OR the two bits together should compliance with the specification. > > Can you clarify whether the spec needs to be changed or what the purpose > of ORing in the VIRTIO_BLK_T_OUT bit is? _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
