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Tsirkin" To: Jason Wang Cc: xuanzhuo@linux.alibaba.com, eperezma@redhat.com, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH V7 19/19] virtio_ring: add in order support Message-ID: <20251014050901-mutt-send-email-mst@kernel.org> References: <20250925103708.44589-1-jasowang@redhat.com> <20250925103708.44589-20-jasowang@redhat.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20250925103708.44589-20-jasowang@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: dg3vDcP_Hgp3mV4u2v4401o9clohb-NOdt6Juw47BAE_1760433222 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Sep 25, 2025 at 06:37:08PM +0800, Jason Wang wrote: > @@ -683,7 +707,12 @@ static inline int virtqueue_add_split(struct vring_virtqueue *vq, > vq->vq.num_free -= descs_used; > > /* Update free pointer */ > - if (indirect) > + if (virtqueue_is_in_order(vq)) { > + vq->free_head += descs_used; > + if (vq->free_head >= vq->split.vring.num) > + vq->free_head -= vq->split.vring.num; > + vq->split.desc_state[head].total_len = total_len;; > + } else if (indirect) > vq->free_head = vq->split.desc_extra[head].next; > else > vq->free_head = i; So in order is clearly doing something funky with the free_head. It's no longer a head of a linked list of free descriptors, is it? what is it doing and why? Please add code comments to explain both where free_list is defined and where it's used. For example, virtqueue_vring_attach_packed only inits free_list if not in order. So who will init it for in order? And so on. -- MST