Xuan Zhuo
2023-Jun-27 08:50 UTC
[PATCH vhost v10 02/10] virtio_ring: introduce virtqueue_set_premapped()
On Tue, 27 Jun 2023 16:03:23 +0800, Jason Wang <jasowang at redhat.com> wrote:> On Fri, Jun 2, 2023 at 5:22?PM Xuan Zhuo <xuanzhuo at linux.alibaba.com> wrote: > > > > This helper allows the driver change the dma mode to premapped mode. > > Under the premapped mode, the virtio core do not do dma mapping > > internally. > > > > This just work when the use_dma_api is true. If the use_dma_api is false, > > the dma options is not through the DMA APIs, that is not the standard > > way of the linux kernel. > > > > Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com> > > --- > > drivers/virtio/virtio_ring.c | 40 ++++++++++++++++++++++++++++++++++++ > > include/linux/virtio.h | 2 ++ > > 2 files changed, 42 insertions(+) > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > index 72ed07a604d4..2afdfb9e3e30 100644 > > --- a/drivers/virtio/virtio_ring.c > > +++ b/drivers/virtio/virtio_ring.c > > @@ -172,6 +172,9 @@ struct vring_virtqueue { > > /* Host publishes avail event idx */ > > bool event; > > > > + /* Do DMA mapping by driver */ > > + bool premapped; > > + > > /* Head of free buffer list. */ > > unsigned int free_head; > > /* Number we've added since last sync. */ > > @@ -2059,6 +2062,7 @@ static struct virtqueue *vring_create_virtqueue_packed( > > vq->packed_ring = true; > > vq->dma_dev = dma_dev; > > vq->use_dma_api = vring_use_dma_api(vdev); > > + vq->premapped = false; > > > > vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) && > > !context; > > @@ -2548,6 +2552,7 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index, > > #endif > > vq->dma_dev = dma_dev; > > vq->use_dma_api = vring_use_dma_api(vdev); > > + vq->premapped = false; > > > > vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) && > > !context; > > @@ -2691,6 +2696,41 @@ int virtqueue_resize(struct virtqueue *_vq, u32 num, > > } > > EXPORT_SYMBOL_GPL(virtqueue_resize); > > > > +/** > > + * virtqueue_set_premapped - set the vring premapped mode > > + * @_vq: the struct virtqueue we're talking about. > > + * > > + * Enable the premapped mode of the vq. > > + * > > + * The vring in premapped mode does not do dma internally, so the driver must > > + * do dma mapping in advance. The driver must pass the dma_address through > > + * dma_address of scatterlist. When the driver got a used buffer from > > + * the vring, it has to unmap the dma address. So the driver must call > > + * virtqueue_get_buf_premapped()/virtqueue_detach_unused_buf_premapped(). > > + * > > + * This must be called before adding any buf to vring. > > And any old buffer should be detached?I mean that before adding any buf, So there are not old buffer.> > > + * So this should be called immediately after init vq or vq reset. > > Any way to detect and warn in this case? (not a must if it's too > expensive to do the check)I can try to check whether the qeueu is empty.> > > + * > > + * 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. > > + * 0: success. > > + * -EINVAL: vring does not use the dma api, so we can not enable premapped mode. > > + */ > > +int virtqueue_set_premapped(struct virtqueue *_vq) > > +{ > > + struct vring_virtqueue *vq = to_vvq(_vq); > > + > > + if (!vq->use_dma_api) > > + return -EINVAL; > > + > > + vq->premapped = true; > > I guess there should be a way to disable it. Would it be useful for > the case when AF_XDP sockets were destroyed?Yes. When we reset the queue, the vq->premapped will be set to 0. The is called after find_vqs or reset vq. Thanks.> > Thanks > > > > + > > + return 0; > > +} > > +EXPORT_SYMBOL_GPL(virtqueue_set_premapped); > > + > > /* 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 b93238db94e3..1fc0e1023bd4 100644 > > --- a/include/linux/virtio.h > > +++ b/include/linux/virtio.h > > @@ -78,6 +78,8 @@ bool virtqueue_enable_cb(struct virtqueue *vq); > > > > unsigned virtqueue_enable_cb_prepare(struct virtqueue *vq); > > > > +int virtqueue_set_premapped(struct virtqueue *_vq); > > + > > bool virtqueue_poll(struct virtqueue *vq, unsigned); > > > > bool virtqueue_enable_cb_delayed(struct virtqueue *vq); > > -- > > 2.32.0.3.g01195cf9f > > >
Michael S. Tsirkin
2023-Jun-27 14:56 UTC
[PATCH vhost v10 02/10] virtio_ring: introduce virtqueue_set_premapped()
On Tue, Jun 27, 2023 at 04:50:01PM +0800, Xuan Zhuo wrote:> On Tue, 27 Jun 2023 16:03:23 +0800, Jason Wang <jasowang at redhat.com> wrote: > > On Fri, Jun 2, 2023 at 5:22?PM Xuan Zhuo <xuanzhuo at linux.alibaba.com> wrote: > > > > > > This helper allows the driver change the dma mode to premapped mode. > > > Under the premapped mode, the virtio core do not do dma mapping > > > internally. > > > > > > This just work when the use_dma_api is true. If the use_dma_api is false, > > > the dma options is not through the DMA APIs, that is not the standard > > > way of the linux kernel. > > > > > > Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com> > > > --- > > > drivers/virtio/virtio_ring.c | 40 ++++++++++++++++++++++++++++++++++++ > > > include/linux/virtio.h | 2 ++ > > > 2 files changed, 42 insertions(+) > > > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > > index 72ed07a604d4..2afdfb9e3e30 100644 > > > --- a/drivers/virtio/virtio_ring.c > > > +++ b/drivers/virtio/virtio_ring.c > > > @@ -172,6 +172,9 @@ struct vring_virtqueue { > > > /* Host publishes avail event idx */ > > > bool event; > > > > > > + /* Do DMA mapping by driver */ > > > + bool premapped; > > > + > > > /* Head of free buffer list. */ > > > unsigned int free_head; > > > /* Number we've added since last sync. */ > > > @@ -2059,6 +2062,7 @@ static struct virtqueue *vring_create_virtqueue_packed( > > > vq->packed_ring = true; > > > vq->dma_dev = dma_dev; > > > vq->use_dma_api = vring_use_dma_api(vdev); > > > + vq->premapped = false; > > > > > > vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) && > > > !context; > > > @@ -2548,6 +2552,7 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index, > > > #endif > > > vq->dma_dev = dma_dev; > > > vq->use_dma_api = vring_use_dma_api(vdev); > > > + vq->premapped = false; > > > > > > vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) && > > > !context; > > > @@ -2691,6 +2696,41 @@ int virtqueue_resize(struct virtqueue *_vq, u32 num, > > > } > > > EXPORT_SYMBOL_GPL(virtqueue_resize); > > > > > > +/** > > > + * virtqueue_set_premapped - set the vring premapped mode > > > + * @_vq: the struct virtqueue we're talking about. > > > + * > > > + * Enable the premapped mode of the vq. > > > + * > > > + * The vring in premapped mode does not do dma internally, so the driver must > > > + * do dma mapping in advance. The driver must pass the dma_address through > > > + * dma_address of scatterlist. When the driver got a used buffer from > > > + * the vring, it has to unmap the dma address. So the driver must call > > > + * virtqueue_get_buf_premapped()/virtqueue_detach_unused_buf_premapped(). > > > + * > > > + * This must be called before adding any buf to vring. > > > > And any old buffer should be detached? > > I mean that before adding any buf, So there are not old buffer. >Oh. So put this in the same sentence: This function must be called immediately after creating the vq, or after vq reset, and before adding any buffers to it.> > > > > + * So this should be called immediately after init vq or vq reset.Do you really need to call this again after each reset?> > Any way to detect and warn in this case? (not a must if it's too > > expensive to do the check) > > > I can try to check whether the qeueu is empty. > > > > > > > + * > > > + * 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. > > > + * 0: success. > > > + * -EINVAL: vring does not use the dma api, so we can not enable premapped mode. > > > + */ > > > +int virtqueue_set_premapped(struct virtqueue *_vq) > > > +{ > > > + struct vring_virtqueue *vq = to_vvq(_vq); > > > + > > > + if (!vq->use_dma_api) > > > + return -EINVAL; > > > + > > > + vq->premapped = true; > > > > I guess there should be a way to disable it. Would it be useful for > > the case when AF_XDP sockets were destroyed? > > Yes. > > When we reset the queue, the vq->premapped will be set to 0. > > The is called after find_vqs or reset vq. > > Thanks. > > > > > > > Thanks > > > > > > > + > > > + return 0; > > > +} > > > +EXPORT_SYMBOL_GPL(virtqueue_set_premapped); > > > + > > > /* 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 b93238db94e3..1fc0e1023bd4 100644 > > > --- a/include/linux/virtio.h > > > +++ b/include/linux/virtio.h > > > @@ -78,6 +78,8 @@ bool virtqueue_enable_cb(struct virtqueue *vq); > > > > > > unsigned virtqueue_enable_cb_prepare(struct virtqueue *vq); > > > > > > +int virtqueue_set_premapped(struct virtqueue *_vq); > > > + > > > bool virtqueue_poll(struct virtqueue *vq, unsigned); > > > > > > bool virtqueue_enable_cb_delayed(struct virtqueue *vq); > > > -- > > > 2.32.0.3.g01195cf9f > > > > >