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virtio_ring: Support DMA APIs

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virtio_ring currently sends the device (usually a hypervisor)
physical addresses of its I/O buffers.  This is okay when DMA
addresses and physical addresses are the same thing, but this isn't
always the case.  For example, this never works on Xen guests, and
it is likely to fail if a physical "virtio" device ever ends up
behind an IOMMU or swiotlb.

The immediate use case for me is to enable virtio on Xen guests.
For that to work, we need vring to support DMA address translation
as well as a corresponding change to virtio_pci or to another
driver.

Signed-off-by: Andy Lutomirski <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
This commit is contained in:
Andy Lutomirski 2016-02-02 21:46:36 -08:00 • committed by Michael S. Tsirkin
commit 780bc7903a
3 changed files with 183 additions and 36 deletions
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17
tools/virtio/linux/dma-mapping.h Normal file
View file

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#ifndef _LINUX_DMA_MAPPING_H
#define _LINUX_DMA_MAPPING_H
#ifdef CONFIG_HAS_DMA
# error Virtio userspace code does not support CONFIG_HAS_DMA
#endif
#define PCI_DMA_BUS_IS_PHYS 1
enum dma_data_direction {
DMA_BIDIRECTIONAL = 0,
DMA_TO_DEVICE = 1,
DMA_FROM_DEVICE = 2,
DMA_NONE = 3,
};
#endif