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Tsirkin" To: Xuan Zhuo Cc: qemu-devel@nongnu.org, Jason Wang , Alexander Bulekov Subject: Re: [PATCH v1 2/2] virtio-net: virtio_net_flush_tx() check for per-queue reset Message-ID: <20230129065705-mutt-send-email-mst@kernel.org> References: <20230129025150.119972-1-xuanzhuo@linux.alibaba.com> <20230129025150.119972-3-xuanzhuo@linux.alibaba.com> <20230129021402-mutt-send-email-mst@kernel.org> <1674977308.9335406-2-xuanzhuo@linux.alibaba.com> <20230129025950-mutt-send-email-mst@kernel.org> <1674980588.489446-5-xuanzhuo@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1674980588.489446-5-xuanzhuo@linux.alibaba.com> Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Sun, Jan 29, 2023 at 04:23:08PM +0800, Xuan Zhuo wrote: > On Sun, 29 Jan 2023 03:12:12 -0500, "Michael S. Tsirkin" wrote: > > On Sun, Jan 29, 2023 at 03:28:28PM +0800, Xuan Zhuo wrote: > > > On Sun, 29 Jan 2023 02:25:43 -0500, "Michael S. Tsirkin" wrote: > > > > On Sun, Jan 29, 2023 at 10:51:50AM +0800, Xuan Zhuo wrote: > > > > > Check whether it is per-queue reset state in virtio_net_flush_tx(). > > > > > > > > > > Before per-queue reset, we need to recover async tx resources. At this > > > > > time, virtio_net_flush_tx() is called, but we should not try to send > > > > > new packets, so virtio_net_flush_tx() should check the current > > > > > per-queue reset state. > > > > > > > > > > > > What does "at this time" mean here? > > > > Do you in fact mean it's called from flush_or_purge_queued_packets? > > > > > > Yes > > > > > > virtio_queue_reset > > > k->queue_reset > > > virtio_net_queue_reset > > > flush_or_purge_queued_packets > > > qemu_flush_or_purge_queued_packets > > > ..... > > > (callback) virtio_net_tx_complete > > > virtio_net_flush_tx <-- here send new packet. We need stop it. > > > > > > > > > Because it is inside the callback, I can't pass information through the stack. I > > > originally thought it was a general situation, so I wanted to put it in > > > struct VirtQueue. > > > > > > If it is not very suitable, it may be better to put it in VirtIONetQueue. > > > > > > Thanks. > > > > Hmm maybe. Another idea: isn't virtio_net_tx_complete called > > with length 0 here? Are there other cases where length is 0? > > > > > > > > What does the call stack look like? > > > > > > > > If yes introducing a vq state just so virtio_net_flush_tx > > > > knows we are in the process of reset would be a bad idea. > > > > We want something much more local, ideally on stack even ... > > > > > > > > > > > > > > > > > > Fixes: 7dc6be52 ("virtio-net: support queue reset") > > > > > Fixes: https://gitlab.com/qemu-project/qemu/-/issues/1451 > > > > > Reported-by: Alexander Bulekov > > > > > Signed-off-by: Xuan Zhuo > > > > > --- > > > > > hw/net/virtio-net.c | 3 ++- > > > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c > > > > > index 3ae909041a..fba6451a50 100644 > > > > > --- a/hw/net/virtio-net.c > > > > > +++ b/hw/net/virtio-net.c > > > > > @@ -2627,7 +2627,8 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q) > > > > > VirtQueueElement *elem; > > > > > int32_t num_packets = 0; > > > > > int queue_index = vq2q(virtio_get_queue_index(q->tx_vq)); > > > > > - if (!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) { > > > > > + if (!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) || > > > > > + virtio_queue_reset_state(q->tx_vq)) { > > > > btw this sounds like you are asking it to reset some state. > > > > > > > return num_packets; > > > > and then > > > > ret = virtio_net_flush_tx(q); > > if (ret >= n->tx_burst) > > > > > > will reschedule automatically won't it? > > > > also why check in virtio_net_flush_tx and not virtio_net_tx_complete? > > virtio_net_flush_tx may been called by timer. > > Thanks. timer won't run while flush_or_purge_queued_packets is in progress. > > > > > > > > > } > > > > > > > > > > -- > > > > > 2.32.0.3.g01195cf9f > > > > > >