Michael S. Tsirkin
2023-Jan-11 14:54 UTC
[PATCH 1/5] virtio_ring: per virtqueue dma device
On Wed, Jan 11, 2023 at 02:46:20PM +0000, Eli Cohen wrote:> > From: Michael S. Tsirkin <mst at redhat.com> > > Sent: Wednesday, 11 January 2023 15:53 > > To: Eli Cohen <elic at nvidia.com> > > Cc: Jason Wang <jasowang at redhat.com>; gdawar at amd.com; > > virtualization at lists.linux-foundation.org; linux-kernel at vger.kernel.org; > > tanuj.kamde at amd.com > > Subject: Re: [PATCH 1/5] virtio_ring: per virtqueue dma device > > > > On Wed, Jan 11, 2023 at 01:32:20PM +0000, Eli Cohen wrote: > > > > From: Jason Wang <jasowang at redhat.com> > > > > Sent: Wednesday, 11 January 2023 8:28 > > > > To: mst at redhat.com; jasowang at redhat.com > > > > Cc: Eli Cohen <elic at nvidia.com>; gdawar at amd.com; > > > > virtualization at lists.linux-foundation.org; linux-kernel at vger.kernel.org; > > > > tanuj.kamde at amd.com > > > > Subject: [PATCH 1/5] virtio_ring: per virtqueue dma device > > > > > > > > This patch introduces a per virtqueue dma device. This will be used > > > > for virtio devices whose virtqueue are backed by different underlayer > > > > devices. > > > > > > > > One example is the vDPA that where the control virtqueue could be > > > > implemented through software mediation. > > > > > > > > Some of the work are actually done before since the helper like > > > > vring_dma_device(). This work left are: > > > > > > > > - Let vring_dma_device() return the per virtqueue dma device instead > > > > of the vdev's parent. > > > > - Allow passing a dma_device when creating the virtqueue through a new > > > > helper, old vring creation helper will keep using vdev's parent. > > > > > > > > Signed-off-by: Jason Wang <jasowang at redhat.com> > > > > --- > > > > drivers/virtio/virtio_ring.c | 133 ++++++++++++++++++++++++----------- > > > > include/linux/virtio_ring.h | 16 +++++ > > > > 2 files changed, 109 insertions(+), 40 deletions(-) > > > > > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > > > index 723c4e29e1d3..41144b5246a8 100644 > > > > --- a/drivers/virtio/virtio_ring.c > > > > +++ b/drivers/virtio/virtio_ring.c > > > > @@ -202,6 +202,9 @@ struct vring_virtqueue { > > > > /* DMA, allocation, and size information */ > > > > bool we_own_ring; > > > > > > > > + /* Device used for doing DMA */ > > > > + struct device *dma_dev; > > > > + > > > > #ifdef DEBUG > > > > /* They're supposed to lock for us. */ > > > > unsigned int in_use; > > > > @@ -219,7 +222,8 @@ static struct virtqueue > > > > *__vring_new_virtqueue(unsigned int index, > > > > bool context, > > > > bool (*notify)(struct virtqueue *), > > > > void (*callback)(struct virtqueue > > > > *), > > > > - const char *name); > > > > + const char *name, > > > > + struct device *dma_dev); > > > > static struct vring_desc_extra *vring_alloc_desc_extra(unsigned int num); > > > > static void vring_free(struct virtqueue *_vq); > > > > > > > > @@ -297,10 +301,11 @@ size_t virtio_max_dma_size(struct virtio_device > > > > *vdev) > > > > EXPORT_SYMBOL_GPL(virtio_max_dma_size); > > > > > > > > static void *vring_alloc_queue(struct virtio_device *vdev, size_t size, > > > > - dma_addr_t *dma_handle, gfp_t flag) > > > > + dma_addr_t *dma_handle, gfp_t flag, > > > > + struct device *dma_dev) > > > > { > > > > if (vring_use_dma_api(vdev)) { > > > > - return dma_alloc_coherent(vdev->dev.parent, size, > > > > + return dma_alloc_coherent(dma_dev, size, > > > > dma_handle, flag); > > > > } else { > > > > void *queue = alloc_pages_exact(PAGE_ALIGN(size), flag); > > > > @@ -330,10 +335,11 @@ static void *vring_alloc_queue(struct > > virtio_device > > > > *vdev, size_t size, > > > > } > > > > > > > > static void vring_free_queue(struct virtio_device *vdev, size_t size, > > > > - void *queue, dma_addr_t dma_handle) > > > > + void *queue, dma_addr_t dma_handle, > > > > + struct device *dma_dev) > > > > { > > > > if (vring_use_dma_api(vdev)) > > > > - dma_free_coherent(vdev->dev.parent, size, queue, > > > > dma_handle); > > > > + dma_free_coherent(dma_dev, size, queue, dma_handle); > > > > else > > > > free_pages_exact(queue, PAGE_ALIGN(size)); > > > > } > > > > @@ -341,11 +347,11 @@ static void vring_free_queue(struct > > virtio_device > > > > *vdev, size_t size, > > > > /* > > > > * The DMA ops on various arches are rather gnarly right now, and > > > > * making all of the arch DMA ops work on the vring device itself > > > > - * is a mess. For now, we use the parent device for DMA ops. > > > > + * is a mess. > > > > */ > > > > static inline struct device *vring_dma_dev(const struct vring_virtqueue > > *vq) > > > > { > > > > - return vq->vq.vdev->dev.parent; > > > > + return vq->dma_dev; > > > > } > > > > > > How about getting rid of this function and just use vq->dma_dev? > > > > Will make the patch even bigger than it is. > > I can't see how this can happen. You get rid of the function and you lose overall 10 lines. What am I missing?This is an existing function, if you drop it you need to refactor more of the existing code. No?> > If you do patch on top pls. >