From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 72A7DC433EF for ; Fri, 11 Feb 2022 07:13:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347639AbiBKHNg (ORCPT ); Fri, 11 Feb 2022 02:13:36 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:36778 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347641AbiBKHNc (ORCPT ); Fri, 11 Feb 2022 02:13:32 -0500 Received: from out30-43.freemail.mail.aliyun.com (out30-43.freemail.mail.aliyun.com [115.124.30.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2B206265A for ; Thu, 10 Feb 2022 23:13:29 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R721e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04407;MF=xuanzhuo@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0V47kTem_1644563606; Received: from localhost(mailfrom:xuanzhuo@linux.alibaba.com fp:SMTPD_---0V47kTem_1644563606) by smtp.aliyun-inc.com(127.0.0.1); Fri, 11 Feb 2022 15:13:27 +0800 Message-ID: <1644563228.441517-2-xuanzhuo@linux.alibaba.com> Subject: Re: [PATCH v4 09/14] virtio: queue_reset: struct virtio_config_ops add callbacks for queue_reset Date: Fri, 11 Feb 2022 15:07:08 +0800 From: Xuan Zhuo To: Jason Wang Cc: "Michael S. Tsirkin" , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <20220209122901.51790-1-xuanzhuo@linux.alibaba.com> <20220209122901.51790-10-xuanzhuo@linux.alibaba.com> <140fc738-3391-5529-dd5a-c46b9e937355@redhat.com> In-Reply-To: <140fc738-3391-5529-dd5a-c46b9e937355@redhat.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 11 Feb 2022 14:49:03 +0800, Jason Wang wrote: > > =E5=9C=A8 2022/2/9 =E4=B8=8B=E5=8D=888:28, Xuan Zhuo =E5=86=99=E9=81=93: > > Performing reset on a queue is divided into four steps: > > > > 1. reset_vq: reset one vq > > 2. recycle the buffer from vq by virtqueue_detach_unused_buf() > > 3. release the ring of the vq by vring_release_virtqueue() > > 4. enable_reset_vq: re-enable the reset queue > > > > So add two callbacks reset_vq, enable_reset_vq to struct > > virtio_config_ops. > > > > Signed-off-by: Xuan Zhuo > > --- > > include/linux/virtio_config.h | 13 +++++++++++++ > > 1 file changed, 13 insertions(+) > > > > diff --git a/include/linux/virtio_config.h b/include/linux/virtio_confi= g.h > > index 4d107ad31149..0d01a64f2576 100644 > > --- a/include/linux/virtio_config.h > > +++ b/include/linux/virtio_config.h > > @@ -74,6 +74,17 @@ struct virtio_shm_region { > > * @set_vq_affinity: set the affinity for a virtqueue (optional). > > * @get_vq_affinity: get the affinity for a virtqueue (optional). > > * @get_shm_region: get a shared memory region based on the index. > > + * @reset_vq: reset a queue individually > > > This needs to be marked as optional I think. OK. > > > > + * vq: the virtqueue > > + * Returns 0 on success or error status > > > It looks to me the caller should also guarantee that the vring is not > accsed by any functions e.g NAPI. OK. > > > > + * After successfully calling this, be sure to call > > + * virtqueue_detach_unused_buf() to recycle the buffer in the ring, and > > + * then call vring_release_virtqueue() to release the vq ring. > > + * @enable_reset_vq: enable a reset queue > > + * vq: the virtqueue > > + * ring_num: specify ring num for the vq to be re-enabled. 0 means use= the > > + * default value. MUST be a power of 2. > > > Note that we don't have power of 2 requirement for packed virtqueue. So the following check here does not seem reasonable. (virtio_pci_modern.c) static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev, struct virtio_pci_vq_info *info, unsigned index, void (*callback)(struct virtqueue *vq), const char *name, bool ctx, u16 msix_vec) { struct virtio_pci_modern_device *mdev =3D &vp_dev->mdev; struct virtqueue *vq; u16 num; int err; if (index >=3D vp_modern_get_num_queues(mdev)) return ERR_PTR(-ENOENT); /* Check if queue is either not available or already active. */ num =3D vp_modern_get_queue_size(mdev, index); if (!num || vp_modern_get_queue_enable(mdev, index)) return ERR_PTR(-ENOENT); if (num & (num - 1)) { dev_warn(&vp_dev->pci_dev->dev, "bad queue size %u", num); return ERR_PTR(-EINVAL); } ^^^^^^^^^^^^^^^^^^^^^^^ > > And I wonder if it's cleaner to have a find_vq() ops instead to dealing > with the re-allocation and possible size change, or have a dedicated > helper to set vring size so driver can do. > > reset_vq() > > virtqueue_set_vring_size() > > enable_reset_vq() I like to add a dedicated helper. > > > > + * Returns 0 on success or error status > > */ > > typedef void vq_callback_t(struct virtqueue *); > > struct virtio_config_ops { > > @@ -100,6 +111,8 @@ struct virtio_config_ops { > > int index); > > bool (*get_shm_region)(struct virtio_device *vdev, > > struct virtio_shm_region *region, u8 id); > > + int (*reset_vq)(struct virtqueue *vq); > > + int (*enable_reset_vq)(struct virtqueue *vq, u16 ring_num); > > > Note that the current implement is best-effort, so it's not guarantee > that we can have a vring with ring_num, we may get less under memory > pressure or even fail. We probably need to have a pamater to mandate the > ring_num otherwise user may surprise to see a decreased size of the ring > when a increasing is actually requested. 1. We can add a helper to specify max ring num. 2. Or after specifying ring num, in case of failure, return directly. I prefer #1 Thanks. > > Thanks > > > > }; > > > > /* If driver didn't advertise the feature, it will never appear. */ >