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 9A528C433F5 for ; Wed, 13 Apr 2022 12:19:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230041AbiDMMV0 (ORCPT ); Wed, 13 Apr 2022 08:21:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51424 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229483AbiDMMV0 (ORCPT ); Wed, 13 Apr 2022 08:21:26 -0400 Received: from out30-45.freemail.mail.aliyun.com (out30-45.freemail.mail.aliyun.com [115.124.30.45]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DFCE85881F; Wed, 13 Apr 2022 05:19:02 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R911e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04357;MF=xuanzhuo@linux.alibaba.com;NM=1;PH=DS;RN=33;SR=0;TI=SMTPD_---0V9zZ.hy_1649852336; Received: from localhost(mailfrom:xuanzhuo@linux.alibaba.com fp:SMTPD_---0V9zZ.hy_1649852336) by smtp.aliyun-inc.com(127.0.0.1); Wed, 13 Apr 2022 20:18:57 +0800 Message-ID: <1649852080.6360478-1-xuanzhuo@linux.alibaba.com> Subject: Re: [PATCH v9 18/32] virtio_ring: introduce virtqueue_resize() Date: Wed, 13 Apr 2022 20:14:40 +0800 From: Xuan Zhuo To: Jason Wang Cc: Jeff Dike , Richard Weinberger , Anton Ivanov , "Michael S. Tsirkin" , "David S. Miller" , Jakub Kicinski , Hans de Goede , Mark Gross , Vadim Pasternak , Bjorn Andersson , Mathieu Poirier , Cornelia Huck , Halil Pasic , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Alexander Gordeev , Sven Schnelle , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , Johannes Berg , Vincent Whitchurch , linux-um@lists.infradead.org, netdev@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-remoteproc@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, bpf@vger.kernel.org, virtualization@lists.linux-foundation.org References: <20220406034346.74409-1-xuanzhuo@linux.alibaba.com> <20220406034346.74409-19-xuanzhuo@linux.alibaba.com> <92622553-e02d-47bd-06f9-0ce24c22650c@redhat.com> In-Reply-To: <92622553-e02d-47bd-06f9-0ce24c22650c@redhat.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On Tue, 12 Apr 2022 14:41:18 +0800, Jason Wang wrote: > > =E5=9C=A8 2022/4/6 =E4=B8=8A=E5=8D=8811:43, Xuan Zhuo =E5=86=99=E9=81=93: > > Introduce virtqueue_resize() to implement the resize of vring. > > Based on these, the driver can dynamically adjust the size of the vring. > > For example: ethtool -G. > > > > virtqueue_resize() implements resize based on the vq reset function. In > > case of failure to allocate a new vring, it will give up resize and use > > the original vring. > > > > During this process, if the re-enable reset vq fails, the vq can no > > longer be used. Although the probability of this situation is not high. > > > > The parameter recycle is used to recycle the buffer that is no longer > > used. > > > > Signed-off-by: Xuan Zhuo > > --- > > drivers/virtio/virtio_ring.c | 69 ++++++++++++++++++++++++++++++++++++ > > include/linux/virtio.h | 3 ++ > > 2 files changed, 72 insertions(+) > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > index 06f66b15c86c..6250e19fc5bf 100644 > > --- a/drivers/virtio/virtio_ring.c > > +++ b/drivers/virtio/virtio_ring.c > > @@ -2554,6 +2554,75 @@ struct virtqueue *vring_create_virtqueue( > > } > > EXPORT_SYMBOL_GPL(vring_create_virtqueue); > > > > +/** > > + * virtqueue_resize - resize the vring of vq > > + * @_vq: the struct virtqueue we're talking about. > > + * @num: new ring num > > + * @recycle: callback for recycle the useless buffer > > + * > > + * When it is really necessary to create a new vring, it will set the = current vq > > + * into the reset state. Then call the passed callback to recycle the = buffer > > + * that is no longer used. Only after the new vring is successfully cr= eated, the > > + * old vring will be released. > > + * > > + * Caller must ensure we don't call this with other virtqueue operatio= ns > > + * at the same time (except where noted). > > + * > > + * Returns zero or a negative error. > > > Should we document that the virtqueue is kept unchanged (still > available) on (specific) failure? > OK. > > > + */ > > +int virtqueue_resize(struct virtqueue *_vq, u32 num, > > + void (*recycle)(struct virtqueue *vq, void *buf)) > > +{ > > + struct vring_virtqueue *vq =3D to_vvq(_vq); > > + struct virtio_device *vdev =3D vq->vq.vdev; > > + bool packed; > > + void *buf; > > + int err; > > + > > + if (!vq->we_own_ring) > > + return -EINVAL; > > + > > + if (num > vq->vq.num_max) > > + return -E2BIG; > > + > > + if (!num) > > + return -EINVAL; > > + > > + packed =3D virtio_has_feature(vdev, VIRTIO_F_RING_PACKED) ? true : fa= lse; > > + > > + if ((packed ? vq->packed.vring.num : vq->split.vring.num) =3D=3D num) > > + return 0; > > + > > + if (!vdev->config->reset_vq) > > + return -ENOENT; > > + > > + if (!vdev->config->enable_reset_vq) > > + return -ENOENT; > > + > > + err =3D vdev->config->reset_vq(_vq); > > + if (err) > > + return err; > > + > > + while ((buf =3D virtqueue_detach_unused_buf(_vq)) !=3D NULL) > > + recycle(_vq, buf); > > + > > + if (packed) { > > + err =3D virtqueue_resize_packed(_vq, num); > > + if (err) > > + virtqueue_reinit_packed(vq); > > > Calling reinit here seems a little bit odd, it looks more like a reset > of the virtqueue. Consider we may re-use virtqueue reset for more > purpose, I wonder if we need a helper like: > > virtqueue_resize() { > =C2=A0=C2=A0=C2=A0 vdev->config->reset_vq(_vq); > =C2=A0=C2=A0=C2=A0 if (packed) > =C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 virtqueue_reinit_packed(_vq) > =C2=A0=C2=A0=C2=A0 else > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 virtqueue_reinit_split(_vq) > } Yes, currently we are implementing resize. This is used to implement set_ringparam() Later, when we implement virtio_net + AF_XDP, what we want is reset not res= ize, so we need to implement a helper: virtqueue_reset() { =C2=A0=C2=A0=C2=A0 vdev->config->reset_vq(_vq); =C2=A0=C2=A0=C2=A0 if (packed) =C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 virtqueue_reinit_packed(_vq) =C2=A0=C2=A0=C2=A0 else =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 virtqueue_reinit_split(_vq) } So I use virtqueue_reinit_* as a separate function not only to deal with the case of resize failure, but also to consider the subsequent implementation = of virtqueue_reset() Thanks. > > Thanks > > > > + } else { > > + err =3D virtqueue_resize_split(_vq, num); > > + if (err) > > + virtqueue_reinit_split(vq); > > + } > > + > > + if (vdev->config->enable_reset_vq(_vq)) > > + return -EBUSY; > > + > > + return err; > > +} > > +EXPORT_SYMBOL_GPL(virtqueue_resize); > > + > > /* Only available for split ring */ > > struct virtqueue *vring_new_virtqueue(unsigned int index, > > unsigned int num, > > diff --git a/include/linux/virtio.h b/include/linux/virtio.h > > index d59adc4be068..c86ff02e0ca0 100644 > > --- a/include/linux/virtio.h > > +++ b/include/linux/virtio.h > > @@ -91,6 +91,9 @@ dma_addr_t virtqueue_get_desc_addr(struct virtqueue *= vq); > > dma_addr_t virtqueue_get_avail_addr(struct virtqueue *vq); > > dma_addr_t virtqueue_get_used_addr(struct virtqueue *vq); > > > > +int virtqueue_resize(struct virtqueue *vq, u32 num, > > + void (*recycle)(struct virtqueue *vq, void *buf)); > > + > > /** > > * virtio_device - representation of a device using virtio > > * @index: unique position on the virtio bus >