This fixes virtio on Xen guests as well as on any other platform
that uses virtio_pci on which physical addresses don't match bus
addresses.

This can be tested with:

    virtme-run --xen xen --kimg arch/x86/boot/bzImage --console

using virtme from here:

    https://git.kernel.org/cgit/utils/kernel/virtme/virtme.git

Without these patches, the guest hangs forever.  With these patches,
everything works.

This should be safe on all platforms that I'm aware of.  That
doesn't mean that there isn't anything that I missed.

Applies to net-next.

Changes from v4:
 - Rebased onto net-next.
 - Dropped the sg end mark changes from virtio_net, as that issue
   is solved differently in net-next.
 - virtio_pci does not use the DMA API on powerpc, for reasons that
   are explained in a detailed comment in virtio_ring.

Changes from v3:
 - virtio_pci only asks virtio_ring to use the DMA API if
   !PCI_DMA_BUS_IS_PHYS.
 - Reduce tools/virtio breakage.  It's now merely as broken as before
   instead of being even more broken.
 - Drop the sg_next changes -- Rusty's version is better.

Changes from v2:
 - Reordered patches.
 - Fixed a virtio_net OOPS.

Changes from v1:
 - Using the DMA API is optional now.  It would be nice to improve the
   DMA API to the point that it could be used unconditionally, but s390
   proves that we're not there yet.
 - Includes patch 4, which fixes DMA debugging warnings from virtio_net.

Andy Lutomirski (3):
  virtio_ring: Support DMA APIs if requested
  virtio_pci: Use the DMA API for virtqueues when possible
  virtio_net: Stop doing DMA from the stack

 drivers/lguest/lguest_device.c         |   3 +-
 drivers/misc/mic/card/mic_virtio.c     |   2 +-
 drivers/net/virtio_net.c               |  53 ++++++---
 drivers/remoteproc/remoteproc_virtio.c |   4 +-
 drivers/s390/kvm/kvm_virtio.c          |   2 +-
 drivers/s390/kvm/virtio_ccw.c          |   4 +-
 drivers/virtio/virtio_mmio.c           |   5 +-
 drivers/virtio/virtio_pci.c            |  91 ++++++++++++++--
 drivers/virtio/virtio_ring.c           | 194 +++++++++++++++++++++++++++------
 include/linux/virtio_ring.h            |   1 +
 tools/virtio/linux/dma-mapping.h       |  17 +++
 tools/virtio/linux/virtio.h            |   1 +
 tools/virtio/virtio_test.c             |   2 +-
 tools/virtio/vringh_test.c             |   3 +-
 14 files changed, 314 insertions(+), 68 deletions(-)
 create mode 100644 tools/virtio/linux/dma-mapping.h

-- 
1.9.3

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