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Commit e6d6dd6c authored by Joerg Roedel's avatar Joerg Roedel Committed by Michael S. Tsirkin
Browse files

virtio: Introduce virtio_max_dma_size() 



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: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 133d624b

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)