[Qemu-devel] [PATCHv2 00/14] virtio-net: iovec handling cleanup

[Michael S. Tsirkin]

virtio net is using lots of manual mangling of iovecs;
I don't see any obvious crashes but it does look scary since guest can
manipulate iovecs.  This patchset changes it to use iov_* functions
which are safer.

On a recent linux kernel, new code will actually do less
iovec processing because it is able to utilize
support for mergeable buffer header size added in
tun/tap in linux 2.6.35 - though I was unable to measure any
speed difference.

This also removes the restriction on buffer layout, aligning qemu with
recent versions of virtio spec which imply that device should be
prepared to handle e.g. virtio net header inline with the packet data in
the same buffer.

Tsted on x86 kvm only for now, would appreciate cross-endianness etc
testing/reports. This is also why I split this to so many small patches
to make bisect easier in case of problems.

Changes from v1: address Anthony's comments
    patches 3,5,8: rename iov_cpy -> iov_copy
    patches 3,4 move hunk that landed in a wrong patch by mistake
    patch 4: move evil cast around so it's localized better

Michael S. Tsirkin (14):
  virtio-net: track host/guest header length
  iov: add const annotation
  iov: add iov_cpy
  virtio-net: avoid sg copy
  virtio-net: use safe iov operations for rx
  virtio-net: refactor receive_hdr
  virtio-net: first s/g is always at start of buf
  virtio-net: switch tx to safe iov functions
  virtio-net: simplify rx code
  virtio: don't mark unaccessed memory as dirty
  virtio-net: fix used len for tx
  virtio-net: minor code simplification
  virtio-net: test peer header support at init time
  virtio-net: enable mrg buf header in tap on linux

 hw/vhost_net.c  |  13 ----
 hw/virtio-net.c | 180 +++++++++++++++++++++++++++++++-------------------------
 hw/virtio.c     |   2 +-
 iov.c           |  25 +++++++-
 iov.h           |  11 +++-
 5 files changed, 134 insertions(+), 97 deletions(-)

-- 
MST