[PATCH v3 0/5] virtio: Clean up scatterlists and use the DMA API

[Andy Lutomirski <luto@amacapital.net>]

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.

Patches 4 and 5 are optional cleanups.  I strongly encourage the
virtio maintainers to apply patch 4, since it should be a very minor
speedup as well as a cleanup, and patch 4 is critical fix if patch 5
is applied.

Patch 5 is last for ease of reversion in case it causes problems.
It is not necessary for DMA mappings to work, and it does not fix
any bugs that I know of.  It's just a cleanup.

Thanks to everyone for putting up with the development of this
series.  Hopefully it'll be the end of DMA issues in virtio. :)

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 (5):
  virtio_ring: Support DMA APIs if requested
  virtio_pci: Use the DMA API for virtqueues
  virtio_net: Stop doing DMA from the stack
  virtio_net: Don't set the end flag on reusable sg entries
  virtio_ring: Remove sg_next indirection

 drivers/lguest/lguest_device.c         |   3 +-
 drivers/misc/mic/card/mic_virtio.c     |   2 +-
 drivers/net/virtio_net.c               |  59 ++++++---
 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            |  35 ++++--
 drivers/virtio/virtio_ring.c           | 219 ++++++++++++++++++++++++++-------
 include/linux/virtio_ring.h            |   1 +
 tools/virtio/linux/virtio.h            |   1 +
 tools/virtio/virtio_test.c             |   2 +-
 tools/virtio/vringh_test.c             |   3 +-
 13 files changed, 256 insertions(+), 84 deletions(-)

-- 
1.9.3