On Feb 3, 2016 5:52 AM, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > > On Tue, Feb 02, 2016 at 09:46:36PM -0800, Andy Lutomirski wrote: > > 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 <luto@xxxxxxxxxx> > > --- > > drivers/virtio/Kconfig | 2 +- > > drivers/virtio/virtio_ring.c | 200 ++++++++++++++++++++++++++++++++------- > > tools/virtio/linux/dma-mapping.h | 17 ++++ > > 3 files changed, 183 insertions(+), 36 deletions(-) > > create mode 100644 tools/virtio/linux/dma-mapping.h > > > > diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig > > index cab9f3f63a38..77590320d44c 100644 > > --- a/drivers/virtio/Kconfig > > +++ b/drivers/virtio/Kconfig > > @@ -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 > > What's this chunk doing here btw? Should be part of the mmio patch? > IIRC it was deliberate. Making virtio depend on HAS_DMA didn't work right because kconfig doesn't propagate dependencies through select intelligently. This patch makes core virtio depend on HAS_DMA, so I added the dependency here, too. --Andy -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
