From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751669AbeD0ESH (ORCPT ); Fri, 27 Apr 2018 00:18:07 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:33540 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751348AbeD0ESG (ORCPT ); Fri, 27 Apr 2018 00:18:06 -0400 Date: Fri, 27 Apr 2018 07:18:03 +0300 From: "Michael S. Tsirkin" To: Jason Wang Cc: Tiwei Bie , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, wexu@redhat.com, jfreimann@redhat.com Subject: Re: [RFC v3 0/5] virtio: support packed ring Message-ID: <20180427071725-mutt-send-email-mst@kernel.org> References: <20180425051550.24342-1-tiwei.bie@intel.com> <5ad1ca01-1e5c-7105-f303-7e8d42f6a068@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5ad1ca01-1e5c-7105-f303-7e8d42f6a068@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 27, 2018 at 11:56:05AM +0800, Jason Wang wrote: > > > On 2018年04月25日 13:15, Tiwei Bie wrote: > > Hello everyone, > > > > This RFC implements packed ring support in virtio driver. > > > > Some simple functional tests have been done with Jason's > > packed ring implementation in vhost: > > > > https://lkml.org/lkml/2018/4/23/12 > > > > Both of ping and netperf worked as expected (with EVENT_IDX > > disabled). But there are below known issues: > > > > 1. Reloading the guest driver will break the Tx/Rx; > > Will have a look at this issue. > > > 2. Zeroing the flags when detaching a used desc will > > break the guest -> host path. > > I still think zeroing flags is unnecessary or even a bug. At host, I track > last observed avail wrap counter and detect avail like (what is suggested in > the example code in the spec): > > static bool desc_is_avail(struct vhost_virtqueue *vq, __virtio16 flags) > { >        bool avail = flags & cpu_to_vhost16(vq, DESC_AVAIL); > >        return avail == vq->avail_wrap_counter; > } > > So zeroing wrap can not work with this obviously. > > Thanks I agree. I think what one should do is flip the available bit. > > > > Some simple functional tests have also been done with > > Wei's packed ring implementation in QEMU: > > > > http://lists.nongnu.org/archive/html/qemu-devel/2018-04/msg00342.html > > > > Both of ping and netperf worked as expected (with EVENT_IDX > > disabled). Reloading the guest driver also worked as expected. > > > > TODO: > > - Refinements (for code and commit log) and bug fixes; > > - Discuss/fix/test EVENT_IDX support; > > - Test devices other than net; > > > > RFC v2 -> RFC v3: > > - Split into small patches (Jason); > > - Add helper virtqueue_use_indirect() (Jason); > > - Just set id for the last descriptor of a list (Jason); > > - Calculate the prev in virtqueue_add_packed() (Jason); > > - Fix/improve desc suppression code (Jason/MST); > > - Refine the code layout for XXX_split/packed and wrappers (MST); > > - Fix the comments and API in uapi (MST); > > - Remove the BUG_ON() for indirect (Jason); > > - Some other refinements and bug fixes; > > > > RFC v1 -> RFC v2: > > - Add indirect descriptor support - compile test only; > > - Add event suppression supprt - compile test only; > > - Move vring_packed_init() out of uapi (Jason, MST); > > - Merge two loops into one in virtqueue_add_packed() (Jason); > > - Split vring_unmap_one() for packed ring and split ring (Jason); > > - Avoid using '%' operator (Jason); > > - Rename free_head -> next_avail_idx (Jason); > > - Add comments for virtio_wmb() in virtqueue_add_packed() (Jason); > > - Some other refinements and bug fixes; > > > > Thanks! > > > > Tiwei Bie (5): > > virtio: add packed ring definitions > > virtio_ring: support creating packed ring > > virtio_ring: add packed ring support > > virtio_ring: add event idx support in packed ring > > virtio_ring: enable packed ring > > > > drivers/virtio/virtio_ring.c | 1271 ++++++++++++++++++++++++++++-------- > > include/linux/virtio_ring.h | 8 +- > > include/uapi/linux/virtio_config.h | 12 +- > > include/uapi/linux/virtio_ring.h | 36 + > > 4 files changed, 1049 insertions(+), 278 deletions(-) > >