[PATCH v5 0/3] virtio: Use the DMA API when appropriate

Andy Lutomirski
2014-09-17T05:22:25Z

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