virtio.4: virtio_pci has no own manpage. Also use .Nm for self-reference.
kernel - Fix signal FP save/restore issues when AVX is enabled

* The kernel was not saving/restoring the full FP context when entering into
  or returning from a signal, leading to corrupt FP registers even when
  AVX is not used, when AVX is enabled in the kernel.

  ANY SIGNAL COULD CORRUPT THE FP STATE.

* Fixed by adjusting the on-user-stack fpsave area sizes and operation.

* This unfortunately changes a number of user visible structures.
  ucontext_t, mcontext_t, sigcontext, sigframe.

  It is POSSIBLE that most userland use cases will be unaffected, but I'm
  not holding my breath.

Major-Sleuthing-by: ftigeot
Testing-by: ftigeot, dillon
Updated the tip URL for the mailing list archives.
if: Multiple TX queue support step 1 of many; introduce ifaltq subqueue

Put the plain queue information, e.g. queue header and tail, serializer,
packet staging scoreboard and ifnet.if_start schedule netmsg etc. into
its own structure (subqueue).  ifaltq structure could have multiple of
subqueues based on the count that drivers can specify.

Subqueue's enqueue, dequeue, purging and states updating are protected
by the subqueue's serializer, so for hardwares supporting multiple TX
queues, contention on queuing operation could be greatly reduced.

The subqueue is passed to if_start to let the driver know which hardware
TX queue to work on.  Only the related driver's TX queue serializer will
be held, so for hardwares supporting multiple TX queues, contention on
driver's TX queue serializer could be greatly reduced.

Bunch of ifsq_ prefixed functions are added, which is used to perform
various operations on subqueues.  Commonly used ifq_ prefixed functions
are still kept mainly for the drivers which do not support multiple TX
queues (well, these functions also ease the netif/ convertion in this
step :).

All of the pseudo network devices under sys/net are converted to use the
new subqueue operation.  netproto/802_11 is converted too.  igb(4) is
converted to use the new subqueue operation, the rest of the network
drivers are only changed for the if_start interface modification.

For ALTQs which have packet scheduler enabled, only the first subqueue
is used (*).

(*) Whether we should utilize multiple TX queues if ALTQ's packet scheduler
is enabled is quite questionable.  Mainly because hardware's multiple TX
queue packet dequeue mechanism could have negative impact on ALTQ's packet
scheduler's decision.
if: Free subqueue memory upon if_detach
if: Multiple TX queue support step 2 of many

ifnet_{serialize,deserialize,tryserialize}_tx and hardware TX serializer
asserion macros now require subqueue, so the proper hardware TX queue's
serializer could be held, released and asserted.
if: Remove unused if_start_nmsg from ifnet

While im here, adjust comment in ifnet a little bit
if: Multiple TX queue support step 3 of 3; map CPUID to subqueue

Add CPUID to subqueue mapping method to ifaltq.  Driver could provide
its own CPUID to subqueue mapping method through ifnet.if_mapsubq,
which is used when ALTQ's packet scheduler is not enabled.  ALTQ's
packet schedulers always map CPUID to the default subqueue.
if: Remove unused IFNET serializer enum, macros and functions.
if: Optimize ifnet_serialize_array_ function a little bit

IFNET_SERIALIZE_ALL is only used on init, stop and configuration path,
which is much less often then IFNET_SERIALIZE_TX; use __predict_false
for IFNET_SERIALIZE_ALL.
sys/param.h: Bump __DragonFly_version due to fpsave area changes
tws(4): Add MSI support.
kernel/usb4bsd: Fix sizeof().
m4: Sync with FreeBSD.

This improves compat with GNU m4 and brings the code closer to NetBSD
and OpenBSD.

Obtained-from:  FreeBSD
Add regression tests for m4.

Obtained-from:  FreeBSD