Commit 780bc790 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Michael S. Tsirkin

virtio_ring: Support DMA APIs

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: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent d26c96c8
......@@ -60,7 +60,7 @@ config VIRTIO_INPUT
config VIRTIO_MMIO
tristate "Platform bus driver for memory mapped virtio devices"
depends on HAS_IOMEM
depends on HAS_IOMEM && HAS_DMA
select VIRTIO
---help---
This drivers provides support for memory mapped virtio
......
This diff is collapsed.
#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
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