Xuan Zhuo
2022-Mar-24 08:34 UTC
[PATCH v8 16/16] virtio_ring: introduce virtqueue_resize()
On Tue, 22 Mar 2022 14:02:47 +0800, Jason Wang <jasowang at redhat.com> wrote:> > ? 2022/3/14 ??5:34, Xuan Zhuo ??: > > 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 at linux.alibaba.com> > > --- > > drivers/virtio/virtio_ring.c | 67 ++++++++++++++++++++++++++++++++++++ > > include/linux/virtio.h | 3 ++ > > 2 files changed, 70 insertions(+) > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > index fb0abf9a2f57..b1dde086a8a4 100644 > > --- a/drivers/virtio/virtio_ring.c > > +++ b/drivers/virtio/virtio_ring.c > > @@ -2528,6 +2528,73 @@ 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 cb 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. > > + * -ENOMEM: create new vring fail. But vq can still work > > + * -EBUSY: reset/re-enable vq fail. vq may cannot work > > + * -ENOENT: not support resize > > + * -E2BIG/-EINVAL: param num error > > + */ > > +int virtqueue_resize(struct virtqueue *vq, u32 num, > > + void (*recycle)(struct virtqueue *vq, void *buf)) > > +{ > > + struct virtio_device *vdev = vq->vdev; > > + void *buf; > > + int err; > > + > > + if (num > vq->num_max) > > + return -E2BIG; > > + > > + if (!num) > > + return -EINVAL; > > + > > + if (to_vvq(vq)->packed.vring.num == num) > > + return 0; > > > Any reason we need to check a packed specific attribute here?This is a mistake. Sorry for this.> > > > + > > + if (!vq->vdev->config->reset_vq) > > + return -ENOENT; > > + > > + if (!vq->vdev->config->enable_reset_vq) > > + return -ENOENT; > > + > > + err = vq->vdev->config->reset_vq(vq); > > + if (err) { > > + if (err != -ENOENT) > > + err = -EBUSY; > > + return err; > > + } > > + > > + while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) > > + recycle(vq, buf); > > + > > + if (virtio_has_feature(vdev, VIRTIO_F_RING_PACKED)) > > + err = virtqueue_resize_packed(vq, num); > > + else > > + err = virtqueue_resize_split(vq, num); > > + > > + if (err) > > + err = -ENOMEM; > > > So this assumes that the -ENOMEM is the only possible error value for > virtqueue_resize_xxx(). Is this true? (E.g wrong size)Yes, I want the user to know at which step the error is returned.> > > > + > > + if (vq->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)); > > > I wonder what's the advantages of coupling virtqueue_reset in > virtqueue_resize().This is Michael's comment on the previous version> > It looks to me it wold be more flexible to let the driver do: > > rest() > > detach() > > resize() > > enable_reset() > > One reason is that in the future we may want to add more functionality > e.g switching PASID during virtqueue reset.Michael, from Jason Wang's plan, should we go back to the original 4 api model? Thanks.> > Thanks > > > > + > > /** > > * virtio_device - representation of a device using virtio > > * @index: unique position on the virtio bus >
Michael S. Tsirkin
2022-Mar-24 10:41 UTC
[PATCH v8 16/16] virtio_ring: introduce virtqueue_resize()
On Thu, Mar 24, 2022 at 04:34:56PM +0800, Xuan Zhuo wrote:> On Tue, 22 Mar 2022 14:02:47 +0800, Jason Wang <jasowang at redhat.com> wrote: > > > > ? 2022/3/14 ??5:34, Xuan Zhuo ??: > > > 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 at linux.alibaba.com> > > > --- > > > drivers/virtio/virtio_ring.c | 67 ++++++++++++++++++++++++++++++++++++ > > > include/linux/virtio.h | 3 ++ > > > 2 files changed, 70 insertions(+) > > > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > > index fb0abf9a2f57..b1dde086a8a4 100644 > > > --- a/drivers/virtio/virtio_ring.c > > > +++ b/drivers/virtio/virtio_ring.c > > > @@ -2528,6 +2528,73 @@ 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 cb 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. > > > + * -ENOMEM: create new vring fail. But vq can still work > > > + * -EBUSY: reset/re-enable vq fail. vq may cannot work > > > + * -ENOENT: not support resize > > > + * -E2BIG/-EINVAL: param num error > > > + */ > > > +int virtqueue_resize(struct virtqueue *vq, u32 num, > > > + void (*recycle)(struct virtqueue *vq, void *buf)) > > > +{ > > > + struct virtio_device *vdev = vq->vdev; > > > + void *buf; > > > + int err; > > > + > > > + if (num > vq->num_max) > > > + return -E2BIG; > > > + > > > + if (!num) > > > + return -EINVAL; > > > + > > > + if (to_vvq(vq)->packed.vring.num == num) > > > + return 0; > > > > > > Any reason we need to check a packed specific attribute here? > > This is a mistake. Sorry for this. > > > > > > > > + > > > + if (!vq->vdev->config->reset_vq) > > > + return -ENOENT; > > > + > > > + if (!vq->vdev->config->enable_reset_vq) > > > + return -ENOENT; > > > + > > > + err = vq->vdev->config->reset_vq(vq); > > > + if (err) { > > > + if (err != -ENOENT) > > > + err = -EBUSY; > > > + return err; > > > + } > > > + > > > + while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) > > > + recycle(vq, buf); > > > + > > > + if (virtio_has_feature(vdev, VIRTIO_F_RING_PACKED)) > > > + err = virtqueue_resize_packed(vq, num); > > > + else > > > + err = virtqueue_resize_split(vq, num); > > > + > > > + if (err) > > > + err = -ENOMEM; > > > > > > So this assumes that the -ENOMEM is the only possible error value for > > virtqueue_resize_xxx(). Is this true? (E.g wrong size) > > Yes, I want the user to know at which step the error is returned. > > > > > > > > + > > > + if (vq->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)); > > > > > > I wonder what's the advantages of coupling virtqueue_reset in > > virtqueue_resize(). > > This is Michael's comment on the previous version > > > > > It looks to me it wold be more flexible to let the driver do: > > > > rest() > > > > detach() > > > > resize() > > > > enable_reset() > > > > One reason is that in the future we may want to add more functionality > > e.g switching PASID during virtqueue reset. > > Michael, from Jason Wang's plan, should we go back to the original 4 api model? > > Thanks.Jason, I feel a single api is preferable, because the need to do reset as part of resize is an implementation detail, I can easily imagine virtio spec being extended with a resize interface which does not require a queue reset. Makes sense to you?> > > > > Thanks > > > > > > > + > > > /** > > > * virtio_device - representation of a device using virtio > > > * @index: unique position on the virtio bus > >