Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r268481:

Rework when the Tx queue completion interrupt is enabled

The Tx interrupt is now kept disabled in the common case, only
enabled when the number of free descriptors in the queue falls
below a threshold. Transmitted frames are cleared from the VQ
before subsequent transmit, or in the watchdog timer.

This was a very big performance improvement for an experimental
Netmap bhyve backend.

MFC r267520, r267521, r267522, r267523, r267524:

- Remove two write-only local variables
- Remove unused element in the vtnet_rxq structure
- Remove kernel specific macro out of the VirtIO PCI header file
- Move the VIRTIO_RING_F_* defines out of virtqueue.h into
virtio_config.h
- Make the feature negotiation code easier to follow
- Force two byte alignment for all control message headers

MFC r261150, r261151, r261164, r261166, r261167, r261168, r261394, r261395:

- Read and write the MAC address in the config space byte by byte
- Also include the mbuf's csum_flags in an assert message
- Remove stray space
- Move duplicated transmit start code into a single function
- Avoid queue unlock followed by relock when the enable interrupt race
is lost
- Check for a full virtqueue in the multiqueue transmit path
- Do not place the sglist used for Rx/Tx on the stack
- Use m_defrag() instead of m_collapse() to compact a long mbuf chain

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Complete any pending Tx frames before attempting the next transmit

Also complete pending frames in the watchdog function when the
EVENT_IDX feature was negotiated just in case the completion
interrupt was postponed.

Import multiqueue VirtIO net driver from my user/bryanv/vtnetmq branch

This is a significant rewrite of much of the previous driver; lots of
misc. cleanup was also performed, and support for a few other minor
features was also added.

Merge virtio changes from projects/virtio

Contains projects/virtio commits:

r245738:
virtio: Minor man page tweaks
r246060:
virtio: Cleanup feature description printing
r246306:
virtio: Remove old debugging flag
r247238:
virtio: Remove PRIx64 macros from format strings
r247239:
virtio: Constify some fields
r247240:
virtio: Minor code simplifications
r249962:
virtio: Update to my freebsd.org email address

MFC after: 1 month

Convert VirtIO to use ithreads instead of taskqueues

Contains projects/virtio commits:

r245709:
Each VirtIO device was scheduling its own taskqueue(9) to do the
off-level interrupt handling. ithreads(9) is the more nature way
to do this. The primary motivation for this work to better support
network multiqueue.
r245710:
virtio: Change virtqueue intr handlers to return void
r245711:
virtio_blk: Remove interrupt taskqueue
r245721:
vtnet: Remove interrupt taskqueue
r245722:
virtio_scsi: Remove interrupt taskqueue
r245747:
vtnet: Remove taskqueue fields missed in r245721

MFC after: 1 month

Catch up with Bryan Venteicher's virtio Hg repo:

c162516
Remove vtblk_sector_size

c162515
Wrap long license lines

c162514
Remove vtblk_unit

c162513
Wrap long lines in the license.

c162512
Remove verbose messages when link goes up/down.

A similar message is printed elsewhere as a result of
if_link_state_change().

c162511
Explicity compare pointer to NULL

c162510
Allocate the mac filter table at attach time.

c162509
Add real BSD licenses to the header files copied from Linux.

The chases upstream changes made in Linux awhile ago.

c162508
Only notify if we actually dequeued something.

c162507
Change a couple of if () { KASSERT(...) } to just KASSERTs.

In non-debug kernels, the if() { } probably get optomized
away, but I guess this is clearer.

c162506
Remove VIRTIO_BLK_F_TOPOLOGY fields in the config.

TOPOLOGY has since been removed from the spec, and the FreeBSD
didn't really do anything with the fields anyways.

c162505
Move vtblk_enqueue_request() outside the locks when getting the ident.

c162504
Remove soon to be uneeded trylock during dump [1].
http://lists.freebsd.org/pipermail/freebsd-current/2011-November/029226.html

c162503
Remove emtpy line

c162502
Drop frame if cannot allocate a vtnet_tx_header.

If we don't, we set OACTIVE, but if there are no
other frames in flight, vtnet_txeof() will never
be called to unset OACTIVE. The interface would
have to be down/up'ed in order to become usable.

We could be cuter here and only do this if the
virtqueue is emtpy, but its probably not worth
the complication.

c162501
Start mbuf replacement loop at 1 for clarity

Obtained from: Bryan Venteicher bryanv at daemoninthecloset dot org

Import virtio base, PCI front-end, and net/block/balloon drivers.
Tested on Qemu/KVM, VirtualBox, and BHyVe.

Currently built as modules-only on i386/amd64. Man pages not yet hooked
up, pending review.

Submitted by: Bryan Venteicher bryanv at daemoninthecloset dot org
Reviewed by: bz
MFC after: 4 weeks or so