MFC r311305 (by asomers):
Always null-terminate ccb_pathinq.(sim_vid|hba_vid|dev_name)

The sim_vid, hba_vid, and dev_name fields of struct ccb_pathinq are
fixed-length strings. AFAICT the only place they're read is in
sbin/camcontrol/camcontrol.c, which assumes they'll be null-terminated.
However, the kernel doesn't null-terminate them. A bunch of copy-pasted code
uses strncpy to write them, and doesn't guarantee null-termination. For at
least 4 drivers (mpr, mps, ciss, and hyperv), the hba_vid field actually
overflows. You can see the result by doing "camcontrol negotiate da0 -v".

This change null-terminates those fields everywhere they're set in the
kernel. It also shortens a few strings to ensure they'll fit within the
16-character field.

PR: 215474
Reported by: Coverity
CID: 1009997 1010000 1010001 1010002 1010003 1010004 1010005
CID: 1331519 1010006 1215097 1010007 1288967 1010008 1306000
CID: 1211924 1010009 1010010 1010011 1010012 1010013 1010014
CID: 1147190 1010017 1010016 1010018 1216435 1010020 1010021
CID: 1010022 1009666 1018185 1010023 1010025 1010026 1010027
CID: 1010028 1010029 1010030 1010031 1010033 1018186 1018187
CID: 1010035 1010036 1010042 1010041 1010040 1010039

MFC r283291: don't use CALLOUT_MPSAFE with callout_init()

The main purpose of this MFC is to reduce conflicts for other merges.
Parts of the original change have already "trickled down" via individual MFCs.

MFC r309119: virtio_pci: fix announcement of MSI-X interrupts for queues

MFC r303971:

Fix vtnet hang with max_virtqueue_pairs > VTNET_MAX_QUEUE_PAIRS

Sponsored by: Multiplay

MFC r267858:

xen/virtio: fix balloon drivers to not mark pages as WIRED

In the Xen case make sure pages are zeroed before giving them back to the
hypervisor, or else we might be leaking data. Also remove the
balloon_{append/retrieve} and link pages directly into the ballooned_pages
queue using the plinks.q field in the page struct.

Sponsored by: Citrix Systems R&D
Requested by: bapt

MFC r284348: Fix panic when adding vtnet interfaces to a bridge

vtnet interfaces are always in promiscuous mode (at least if the
VIRTIO_NET_F_CTRL_RX feature is not negotiated with the host). if_promisc() on
a vtnet interface returned ENOTSUP although it has IFF_PROMISC set. This
confused the bridge code. Instead we now accept all enable/disable promiscuous
commands (and always keep IFF_PROMISC set).

There are also two issues with the if_bridge error handling.

If if_promisc() fails it uses bridge_delete_member() to clean up. This tries to
disable promiscuous mode on the interface. That runs into an assert, because
promiscuous mode was never set in the first place. (That's the panic reported in
PR 200210.)
We can only unset promiscuous mode if the interface actually is promiscuous.
This goes against the reference counting done by if_promisc(), but only the
first/last if_promic() calls can actually fail, so this is safe.

A second issue is a double free of bif. It's already freed by
bridge_delete_member().

PR: 200210

MFC r277788:

Rework vtblk dump handling of in flight requests

Previously, the driver resets the device and abandon the requests that
are caught in flight when the dump was initiated. This was problematic
if the system is resumed after the dump is completed.

While that is probably not the typical action, it is simple to rework
the driver to very likely have the device usable after the dump without
making it more likely for the dump to fail. The in flight requests are
simply queued for completion once the dump is finished.

MFC 282241:
Don't free mbufs when stopping an interface in netmap mode.

Currently if you ifconfig down a vtnet interface while it is being used
via netmap, the kernel panics due to trying to treat the cookie values
in the virtio rings as mbufs to be freed. When netmap is enabled, these
cookie values are pointers to something else.

Note that other netmap-aware drivers don't seem to need this as they
store the mbuf pointers in the software rings that mirror the hardware
descriptor rings, and since netmap doesn't touch those, the software
state always has NULL mbuf pointers causing the loops to free mbufs to
not do anything. However, vtnet reuses the same state area for both
netmap and non-netmap mode, so it needs to explicitly avoid looking at
the rings and treating the cookie values as mbufs if netmap is
enabled.

Sponsored by: Norse Corp, Inc.

MFC r281698:
Do not report stripe size if it is equal to sector size.

MFC r275358 r275483 r276982 - Removing M_FLOWID by hps@

r275358:
Start process of removing the use of the deprecated "M_FLOWID" flag
from the FreeBSD network code. The flag is still kept around in the
"sys/mbuf.h" header file, but does no longer have any users. Instead
the "m_pkthdr.rsstype" field in the mbuf structure is now used to
decide the meaning of the "m_pkthdr.flowid" field. To modify the
"m_pkthdr.rsstype" field please use the existing "M_HASHTYPE_XXX"
macros as defined in the "sys/mbuf.h" header file.

This patch introduces new behaviour in the transmit direction.
Previously network drivers checked if "M_FLOWID" was set in "m_flags"
before using the "m_pkthdr.flowid" field. This check has now now been
replaced by checking if "M_HASHTYPE_GET(m)" is different from
"M_HASHTYPE_NONE". In the future more hashtypes will be added, for
example hashtypes for hardware dedicated flows.

"M_HASHTYPE_OPAQUE" indicates that the "m_pkthdr.flowid" value is
valid and has no particular type. This change removes the need for an
"if" statement in TCP transmit code checking for the presence of a
valid flowid value. The "if" statement mentioned above is now a direct
variable assignment which is then later checked by the respective
network drivers like before.

r275483:
Remove M_FLOWID from SCTP code.

r276982:
Remove no longer used "M_FLOWID" flag from mbuf.h and update the netisr
manpage.

Note: The FreeBSD version has been bumped.

Reviewed by: hps, tuexen
Sponsored by: Limelight Networks

MFC r280090: Hide virtio features negotiation messages under bootverbose.

Those messages are noisy, but useless for average user.

MFC r279651, r279652, r279657:
Add support for TOPOLOGY feature of virtio block device.

Passing through physical block size/offset from underlying storage allows
guest to manage proper data and I/O alignment to improve performance.

MFC r279642: Reenable VIRTIO_BLK_F_TOPOLOGY feature.

MFC r276491:

Add softc flag for when the indirect descriptor feature was negotiated

MFC r276489:

Use the appropriate IPv4 or IPv6 TSO HW assist flag

MFC r275335:

Cleanup and performance improvement of the virtio_blk driver

- Add support for GEOM direct completion. Depending on the benchmark,
this tends to give a ~30% improvement w.r.t IOPs and BW.
- Remove an invariants check in the strategy routine. This assertion
is caught later on by an existing panic.
- Rename and resort various related functions to make more sense.

MFC r274819:
Prevent overflow issues in timeout processing

MFC r274852:
Fix build with asr driver

Sponsored by: Multiplay

MFC r274325:

Enable LRO by default when available on vtnet interfaces

The prior change to not enable LRO by default has confused several
people. The configurations where LRO is problematic is not the
typical use case for VirtIO, and due to other issues, this often
requires checksum offloading to be disabled anyways.

MFC r273515, r274055, r274063, r274215, r274065, r274502:

Add VirtIO console driver.

MFC r270063 (vtnet)

The vtnet changes were not originally merged in r270252 since
r268480 and r268481 had not been MFC'ed.

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 r268480:

Add accessor to get the number of free descriptors in the virtqueue

MFC 260847,264055,264867:
- Add a very simple virtio_random(4) driver for FreeBSD guests to harvest
entropy from hypervisors.
- Add support to bhyve for the virtio RNG entropy-source device to provide
entry to bhyve guests.

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 r267313:

Always append new bios to the tail of the queue, instead of sorting them

MFC r266951:

Split the virtio.h header file into multiple files

Reorganize the previous contexts of the file as it is in Linux. The
eventual goal is to install the header files and share them between
the kernel and bhyve.

MFC svn 267065 and 267187

make sure ifp->if_transmit returns 0 if a buffer is enqueued.
This should also be merged to stable/9.

After this fix, drivers still known to have this bug are igxbe/ixv
and i40e.

Drivers using if_transmit are correct, and so are most of the
other drivers that reassing if_transmit.

Among other things, this bug causes panics when using netmap emulation
on top of generic drivers.

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

MFC r261147:
Remove spaces before tabs in the function prototype list
MFC r261149:
Read each field of the configuration individually

MFC r260583: Add unmapped IO support to virtio_scsi(4)

MFC r260582: Add unmapped IO support to virtio_blk(4)

MFC r260566: Remove incorrect bit shift when assigning the LUN request field

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

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

Do not hold the vtnet Rx queue lock when calling up into the stack

This matches other similar drivers and avoids various LOR warnings.

Approved by: re (marius)

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.

Fix unintended compiler constant folding

Pointed out by: dim@

Fix build with gcc

Reported by: Michael Butler <imb@protected-networks.net>
Reviewed by: jilles

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.

Sync VirtIO net device header file from recent Linux

Add optional VirtIO device method for post-attach notifications

This is called after the parent device (ie virito_pci) has
completed the device attachment/initialization.

Add support for postponing VirtIO virtqueue interrupts

Partial support for the EVENT_IDX feature was added a while ago,
but this commit adds an interface for the device driver to hint
how long (in terms of descriptors) the next interrupt should be
delayed.

The first user of this will be used to reduce VirtIO net's Tx
completion interrupts.

Different consumers of the struct vm_page abuse pageq member to keep
additional information, when the page is guaranteed to not belong to a
paging queue. Usually, this results in a lot of type casts which make
reasoning about the code correctness harder.

Sometimes m->object is used instead of pageq, which could cause real
and confusing bugs if non-NULL m->object is leaked. See r141955 and
r253140 for examples.

Change the pageq member into a union containing explicitly-typed
members. Use them instead of type-punning or abusing m->object in x86
pmaps, uma and vm_page_alloc_contig().

Requested and reviewed by: alc
Sponsored by: The FreeBSD Foundation

Merge virtio_scsi change from projects/virtio

r252680:
Fix SIM lock not owned panic

The CAM locking requirements of registering an async
callback has changed so the SIM lock must be held. Remove
code that explicitly dropped the lock around the register.

Also return CAM_SEL_TIMEOUT instead of CAM_TID_INVALID
for bad targets to avoid a lot console spam during bus
scans.

MFC after: 1 month

Merge virtio_pci changes from projects/virtio

This commit is primarily a significant cleanup to the interrupt
allocation code that had gotten a bit jumbled from having to
support per-vq MSIX, shared MSIX, MSI, and legacy style interrupts.

Contains projects/virtio commits:

r246064:
virtio_pci: Rewrite allocation of interrupts
r246065:
virtio_pci: Remove spaces before a tab
r246066:
virtio_pci: Dynamically allocate the virtqueue array
r246304:
virtio_pci: Clean up after failed virtqueue alloc attempt
r246305:
virtio_pci: Move no interrupt check into the PCI interrupt handlers
r246308:
virtio_pci: Remove unused variable

MFC after: 1 month

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

Merge vtnet changes from projects/virtio

Minor changes to the network driver. A multiqueue driver that is
a significant rewrite will be in merged shortly.

Contains projects/virtio commits:

r246058:
vtnet: Move an mbuf ASSERT to the calling function
r246059:
vtnet: Tweak ASSERT message

MFC after: 1 month

Merge virtio_balloon changes from projects/virtio

Contains projects/virtio commits:

r245717:
virtio_balloon: Make the softc lock a regular mutex
r245718:
virtio_balloon: Remove two unuseful ASSERTs
r245719:
virtio_balloon: More verbose ASSERT messages
r245720:
virtio_balloon: Simplify lowmem handling in vtballoon_inflate()
r252530:
virtio_balloon: Use just a kthread instead of dedciated kproc
r252568:
virtio_balloon: Need to use kthread_exit() after r252530

MFC after: 1 month

Merge several virtio_blk changes from projects/virtio

The notable changes of this commit are support for disk resizing
and chases updates to the spec regarding write caching.

Contains projects/virtio commits:

r245713:
virtio_blk: Replace __FUNCTION__ with __func__
r245714:
virtio_blk: Use more consistent mutex name
r245715:
virtio_blk: Print device name too if failed to reinit during dump
r245716:
virtio_blk: Remove an unuseful ASSERT
r245723:
virtio_blk: Record the vendor and device information
r245724:
virtio_blk: Add resize support
r245726:
virtio_blk: More verbose ASSERT messages
r245730:
virtio_blk: Tweak resize announcement message
r246061:
virtio_blk: Do not always read entire config
r246062:
virtio_blk: Use topology to set the stripe size/offset
r246307:
virtio_blk: Correct stripe offset calculation
r246063:
virtio_blk: Add support for write cache enable feature
r246303:
virtio_blk: Expand a comment
r252529:
virtio_blk: Improve write cache handling
r252681:
virtio_blk: Remove unneeded curly braces

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

Merge r250802 from bryanv/vtnetmq - Fix setting of the Rx filters

QEMU 1.4 made the descriptor requirement stricter - the size of buffer
descriptor must exactly match the number of MAC addresses provided.

PR: kern/178955
MFC after: 5 days

MFprojects/camlock r248982:
Stop abusing xpt_periph in random plases that really have no periph related
to CCB, for example, bus scanning. NULL value is fine in such cases and it
is correctly logged in debug messages as "noperiph". If at some point we
need some real XPT periphs (alike to pmpX now), quite likely they will be
per-bus, and not a single global instance as xpt_periph now.

Only set the barrier flag if the feature was negotiated

When the VirtIO barrier feature is not negotiated, the driver
must enforce the proper ordering for BIO_ORDERED BIOs. All the
in-flight BIOs must complete before starting the BIO, and the
ordered BIO must complete before subsequent BIOs can start.

Also fix a few whitespace nits.

Reported by: neel
Approved by: grehan (mentor)
MFC after: 3 days

Reform the busdma API so that new types may be added without modifying
every architecture's busdma_machdep.c. It is done by unifying the
bus_dmamap_load_buffer() routines so that they may be called from MI
code. The MD busdma is then given a chance to do any final processing
in the complete() callback.

The cam changes unify the bus_dmamap_load* handling in cam drivers.

The arm and mips implementations are updated to track virtual
addresses for sync(). Previously this was done in a type specific
way. Now it is done in a generic way by recording the list of
virtuals in the map.

Submitted by: jeff (sponsored by EMC/Isilon)
Reviewed by: kan (previous version), scottl,
mjacob (isp(4), no objections for target mode changes)
Discussed with: ian (arm changes)
Tested by: marius (sparc64), mips (jmallet), isci(4) on x86 (jharris),
amd64 (Fabian Keil <freebsd-listen@fabiankeil.de>)

virtio: Start taskqueues threads after attach cannot fail

If virtio_setup_intr() failed during boot, we would hang in
taskqueue_free() -> taskqueue_terminate() for all the taskq
threads to terminate. This will never happen since the
scheduler is not running by this point.

Reported by: neel, grehan
Approved by: grehan (mentor)

virtio_scsi: Remove duplicated lines

These must have been accidently copied from the if statement a few
lines later. Also remove parameter name from function prototype.

Approved by: grehan (mentor)

Mechanically substitute flags from historic mbuf allocator with
malloc(9) flags in sys/dev.

Fix build with PAE enabled. I doubt any code uses CAM_SCATTER_VALID or
CAM_DATA_PHYS, or they ever correctly worked, but make this build at least.

Virtio SCSI driver

Submitted by: Bryan Venteicher bryanv at daemoninthecloset dot org
Reviewed by: grehan

Patch from Bryan to fix a virtqueue issue:

virtqueue: Fix non-indirect virtqueues

We really must walk the entire descriptor chain in order
to append the to be free'd chain to the existing free
chain.

Submitted by: Bryan Venteicher (bryanv@daemoninthecloset.org)
Reported by: cognet

Revert previous commit...

Pointyhat to: kevlo (myself)

Prefer NULL over 0 for pointers

No need to leak these into the includer's namespace.

Submitted by: Bryan Venteicher bryanv at daemoninthecloset org

Relax requirement of certain mb()s

Submitted by: Bryan Venteicher bryanv at daemoninthecloset org

Various VirtIO improvements

PCI:
- Properly handle interrupt fallback from MSIX to MSI to legacy.
The host may not have sufficient resources to support MSIX,
so we must be able to fallback to legacy interrupts.
- Add interface to get the (sub) vendor and device IDs.
- Rename flags to VTPCI_FLAG_* like other VirtIO drivers.
Block:
- No longer allocate vtblk_requests from separate UMA zone.
malloc(9) from M_DEVBUF is sufficient. Assert segment counts
at allocation.
- More verbose error and debug messages.
Network:
- Remove stray write once variable.
Virtqueue:
- Shuffle code around in preparation of converting the mb()s to
the appropriate atomic(9) operations.
- Only walk the descriptor chain when freeing if INVARIANTS is
defined since the result is only KASSERT()ed.

Submitted by: Bryan Venteicher (bryanv@daemoninthecloset.org)

Do not include <sys/types.h> in the local headers. The .c files including
them have already included <sys/param.h> before these headers are included.

Sync with Bryan Venteicher's virtio git repo:

d04e609bdd1973cc7d2e8b38b7dcfae057b0962d
virtio_blk: Use correct temporary variable in vtblk_poll_request

Obtained from: Bryan Venteicher bryanv at daemoninthecloset dot org

Catch up with Bryan Venteicher's virtio git repo:

a8af6270bd96be6ccd86f70b60fa6512b710e4f0
virtio_blk: Include function name in panic string

cbdb03a694b76c5253d7ae3a59b9995b9afbb67a
virtio_balloon: Do the notify outside of the lock

By the time we return from virtqueue_notify(), the descriptor
will be in the used ring so we shouldn't have to sleep.

10ba392e60692529a5cbc1e9987e4064e0128447
virtio: Use DEVMETHOD_END

80cbcc4d6552cac758be67f0c99c36f23ce62110
virtqueue: Add support for VIRTIO_F_RING_EVENT_IDX

This can be used to reduce the number of guest/host and
host/guest interrupts by delaying the interrupt until a
certain index value is reached.

Actual use by the network driver will come along later.

8fc465969acc0c58477153e4c3530390db436c02
virtqueue: Simplify virtqueue_nused()

Since the values just wrap naturally at UINT16_MAX, we
can just subtract the two values directly, rather than
doing 2's complement math.

a8aa22f25959e2767d006cd621b69050e7ffb0ae
virtio_blk: Remove debugging crud from 75dd732a

There seems to be an issue with Qemu (or FreeBSD VirtIO) that sets
the PCI register space for the device config to bogus values. This
only seems to happen after unloading and reloading the module.

d404800661cb2a9769c033f8a50b2133934501aa
virtio_blk: Use better variable name

75dd732a97743d96e7c63f7ced3c2169696dadd3
virtio_blk: Partially revert 92ba40e65

Just use the virtqueue to determine if any requests are
still inflight.

06661ed66b7a9efaea240f99f414c368f1bbcdc7
virtio_blk: error if allowed too few segments

Should never happen unless the host provides use with a
bogus seg_max value.

4b33e5085bc87a818433d7e664a0a2c8f56a1a89
virtio_blk: Sort function declarations

426b9f5cac892c9c64cc7631966461514f7e08c6
virtio_blk: Cleanup whitespace

617c23e12c61e3c2233d942db713c6b8ff0bd112
virtio_blk: Call disk_err() on error'd completed requests

081a5712d4b2e0abf273be4d26affcf3870263a9
virtio_blk: ASSERT the ready and inflight request queues are empty

a9be2631a4f770a84145c18ee03a3f103bed4ca8
virtio_blk: Simplify check for too many segments

At the cost of a small style violation.

e00ec09da014f2e60cc75542d0ab78898672d521
virtio_blk: Add beginnings of suspend/resume

Still not sure if we need to virtio_stop()/virtio_reinit()
the device before/after a suspend.

Don't start additional IO when marked as suspending.

47c71dc6ce8c238aa59ce8afd4bda5aa294bc884
virtio_blk: Panic when dealt an unhandled BIO cmd

1055544f90fb8c0cc6a2395f5b6104039606aafe
virtio_blk: Add VQ enqueue/dequeue wrappers

Wrapper functions managed the added/removing to the in-flight
list of requests.

Normally biodone() any completed IO when draining the virtqueue.

92ba40e65b3bb5e4acb9300ece711f1ea8f3f7f4
virtio_blk: Add in-flight list of requests

74f6d260e075443544522c0833dc2712dd93f49b
virtio_blk: Rename VTBLK_FLAG_DETACHING to VTBLK_FLAG_DETACH

7aa549050f6fc6551c09c6362ed6b2a0728956ef
virtio_blk: Finish all BIOs through vtblk_finish_bio()

Also properly set bio_resid in the case of errors. Most geom_disk
providers seem to do the same.

9eef6d0e6f7e5dd362f71ba097f2e2e4c3744882
Added function to translate VirtIO status to error code

ef06adc337f31e1129d6d5f26de6d8d1be27bcd2
Reset dumping flag when given unexpected parameters

393b3e390c644193a2e392220dcc6a6c50b212d9
Added missing VTBLK_LOCK() in dump handler

Obtained from: Bryan Venteicher bryanv at daemoninthecloset dot org

Use pci_find_cap() instead of pci_find_extcap() to locate PCI
find capabilities as the latter API is deprecated for this purpose.

MFC after: 2 weeks

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