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| author | Michael S. Tsirkin <mst@redhat.com> | 2013-07-11 16:06:46 +0300 |
|---|---|---|
| committer | Michael S. Tsirkin <mst@redhat.com> | 2013-07-15 21:26:26 +0300 |
| commit | 488f069bd1f3aeb6ee748acb02b7581831bcb3f8 (patch) | |
| tree | 2a696b07fe49fe6e76293d4882fa0467e2d29338 /include/hw/virtio/virtio-net.h | |
| parent | b1be42803b31a913bab65bab563a8760ad2e7f7f (diff) | |
| download | qemu-488f069bd1f3aeb6ee748acb02b7581831bcb3f8.zip qemu-488f069bd1f3aeb6ee748acb02b7581831bcb3f8.tar.gz qemu-488f069bd1f3aeb6ee748acb02b7581831bcb3f8.tar.bz2 | |
virtio-net: add feature bit for any header s/g
Old qemu versions required that 1st s/g entry is the header.
Since QEMU 1.5, patchset titled "virtio-net: iovec handling cleanup"
removed this limitation but a feature bit is needed so guests know it's
safe to lay out header differently.
This patch applies on top and adds such a feature bit to QEMU.
It is set by default for virtio-net.
virtio net header inline with the data is beneficial
for latency and small packet bandwidth - guest driver
code utilizing this feature has been acked but missed 3.11
by a narrow margin, it's pending for 3.12.
This feature bit is cleared by default when compatibility with old
machine types is requested.
Other performance-sensitive devices (blk and scsi)
don't yet support arbitrary s/g layouts, so
we only set this bit for virtio-net for now.
There are plans to allow arbitrary layouts there, but
no code has been posted yet.
Cc: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'include/hw/virtio/virtio-net.h')
| -rw-r--r-- | include/hw/virtio/virtio-net.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h index b315ac9..df60f16 100644 --- a/include/hw/virtio/virtio-net.h +++ b/include/hw/virtio/virtio-net.h @@ -243,6 +243,7 @@ struct virtio_net_ctrl_mq { #define DEFINE_VIRTIO_NET_FEATURES(_state, _field) \ DEFINE_VIRTIO_COMMON_FEATURES(_state, _field), \ + DEFINE_PROP_BIT("any_layout", _state, _field, VIRTIO_F_ANY_LAYOUT, true), \ DEFINE_PROP_BIT("csum", _state, _field, VIRTIO_NET_F_CSUM, true), \ DEFINE_PROP_BIT("guest_csum", _state, _field, VIRTIO_NET_F_GUEST_CSUM, true), \ DEFINE_PROP_BIT("gso", _state, _field, VIRTIO_NET_F_GSO, true), \ |