virtio: Introduce virtio_max_dma_size() (e6d6dd6c) · Commits · 戴 / test

This function returns the maximum segment size for a single dma transaction of a virtio device. The possible limit comes from the SWIOTLB implementation in the Linux kernel, that has an upper limit of (currently) 256kb of contiguous memory it can map. Other DMA-API implementations might also have limits. Use the new dma_max_mapping_size() function to determine the maximum mapping size when DMA-API is in use for virtio. Cc: stable@vger.kernel.org Reviewed-by:

Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Reviewed-by:

Christoph Hellwig <hch@lst.de> Signed-off-by:

Joerg Roedel <jroedel@suse.de> Signed-off-by:

Michael S. Tsirkin <mst@redhat.com>

drivers/virtio/virtio_ring.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -271,6 +271,17 @@ static bool vring_use_dma_api(struct virtio_device *vdev)
		return false;
		}

		size_t virtio_max_dma_size(struct virtio_device *vdev)
		{
		size_t max_segment_size = SIZE_MAX;

		if (vring_use_dma_api(vdev))
		max_segment_size = dma_max_mapping_size(&vdev->dev);

		return max_segment_size;
		}
		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)
		{

include/linux/virtio.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -157,6 +157,8 @@ int virtio_device_freeze(struct virtio_device *dev);
		int virtio_device_restore(struct virtio_device *dev);
		#endif

		size_t virtio_max_dma_size(struct virtio_device *vdev);

		#define virtio_device_for_each_vq(vdev, vq) \
		list_for_each_entry(vq, &vdev->vqs, list)

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