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Message-ID: <1649852080.6360478-1-xuanzhuo@linux.alibaba.com> Date: Wed, 13 Apr 2022 20:14:40 +0800 From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com> To: Jason Wang <jasowang@...hat.com> Cc: Jeff Dike <jdike@...toit.com>, Richard Weinberger <richard@....at>, Anton Ivanov <anton.ivanov@...bridgegreys.com>, "Michael S. Tsirkin" <mst@...hat.com>, "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Hans de Goede <hdegoede@...hat.com>, Mark Gross <markgross@...nel.org>, Vadim Pasternak <vadimp@...dia.com>, Bjorn Andersson <bjorn.andersson@...aro.org>, Mathieu Poirier <mathieu.poirier@...aro.org>, Cornelia Huck <cohuck@...hat.com>, Halil Pasic <pasic@...ux.ibm.com>, Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>, Alexander Gordeev <agordeev@...ux.ibm.com>, Sven Schnelle <svens@...ux.ibm.com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>, Johannes Berg <johannes.berg@...el.com>, Vincent Whitchurch <vincent.whitchurch@...s.com>, linux-um@...ts.infradead.org, netdev@...r.kernel.org, platform-driver-x86@...r.kernel.org, linux-remoteproc@...r.kernel.org, linux-s390@...r.kernel.org, kvm@...r.kernel.org, bpf@...r.kernel.org, virtualization@...ts.linux-foundation.org Subject: Re: [PATCH v9 18/32] virtio_ring: introduce virtqueue_resize() On Tue, 12 Apr 2022 14:41:18 +0800, Jason Wang <jasowang@...hat.com> wrote: > > 在 2022/4/6 上午11:43, Xuan Zhuo 写道: > > 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 <xuanzhuo@...ux.alibaba.com> > > --- > > 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 created, the > > + * old vring will be released. > > + * > > + * Caller must ensure we don't call this with other virtqueue operations > > + * 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 = to_vvq(_vq); > > + struct virtio_device *vdev = 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 = virtio_has_feature(vdev, VIRTIO_F_RING_PACKED) ? true : false; > > + > > + if ((packed ? vq->packed.vring.num : vq->split.vring.num) == num) > > + return 0; > > + > > + if (!vdev->config->reset_vq) > > + return -ENOENT; > > + > > + if (!vdev->config->enable_reset_vq) > > + return -ENOENT; > > + > > + err = vdev->config->reset_vq(_vq); > > + if (err) > > + return err; > > + > > + while ((buf = virtqueue_detach_unused_buf(_vq)) != NULL) > > + recycle(_vq, buf); > > + > > + if (packed) { > > + err = 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() { > vdev->config->reset_vq(_vq); > if (packed) > virtqueue_reinit_packed(_vq) > else > 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 resize, so we need to implement a helper: virtqueue_reset() { vdev->config->reset_vq(_vq); if (packed) virtqueue_reinit_packed(_vq) else 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 = 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 >
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