Commit Graph

217947 Commits

Author SHA1 Message Date
Ed Maste
9d99bb0a0a Use explicit 0x200000 instead of MAXPAGESIZE for the amd64 kernel physaddr
MAXPAGESIZE is not well defined by the GNU ld documentation.
Different linkers, and different versions of the same linker, use
different MAXPAGESIZE values. Current versions of GNU gold and LLVM's
lld use 4K. When set to 4K the kernel panics at boot due to an issue
with x86bios.

Here we want the kernel physaddr to be the amd64 superpage size, so use
that value (2MB) explicitly. With this change GNU gold and LLVM lld can
link a working amd64 kernel.

PR:		214718 (x86bios)
Differential Revision:	https://reviews.freebsd.org/D8610
2016-11-25 18:57:14 +00:00
Dimitry Andric
d52fad0e5d Bump FREEBSD_CC_VERSION again for r309147 and 309149. 2016-11-25 18:12:57 +00:00
Dimitry Andric
11c1fce83a Pull in r283060 from upstream llvm trunk (by Hal Finkel):
[PowerPC] Refactor soft-float support, and enable PPC64 soft float

  This change enables soft-float for PowerPC64, and also makes
  soft-float disable all vector instruction sets for both 32-bit and
  64-bit modes. This latter part is necessary because the PPC backend
  canonicalizes many Altivec vector types to floating-point types, and
  so soft-float breaks scalarization support for many operations. Both
  for embedded targets and for operating-system kernels desiring
  soft-float support, it seems reasonable that disabling hardware
  floating-point also disables vector instructions (embedded targets
  without hardware floating point support are unlikely to have Altivec,
  etc. and operating system kernels desiring not to use floating-point
  registers to lower syscall cost are unlikely to want to use vector
  registers either). If someone needs this to work, we'll need to
  change the fact that we promote many Altivec operations to act on
  v4f32. To make it possible to disable Altivec when soft-float is
  enabled, hardware floating-point support needs to be expressed as a
  positive feature, like the others, and not a negative feature,
  because target features cannot have dependencies on the disabling of
  some other feature. So +soft-float has now become -hard-float.

  Fixes PR26970.

Pull in r283061 from upstream clang trunk (by Hal Finkel):

  [PowerPC] Enable soft-float for PPC64, and +soft-float -> -hard-float

  Enable soft-float support on PPC64, as the backend now supports it.
  Also, the backend now uses -hard-float instead of +soft-float, so set
  the target features accordingly.

  Fixes PR26970.

Reported by:	Mark Millard
PR:		214433
2016-11-25 18:12:13 +00:00
John Baldwin
9f3aabb9eb Permit timed sleeps for threads other than thread0 before timers are working.
The callout subsystem already handles early callouts and schedules
the first clock interrupt appropriately based on the currently pending
callouts.  The one nit to fix was that callouts scheduled via C_HARDCLOCK
during early boot could fire too early once timers were enabled as the
per-CPU base time is always zero until timers are initialized.  The change
in callout_when() handles this case by using the current uptime as the
base time of the callout during bootup if the per-CPU base time is zero.

Reviewed by:	kib
MFC after:	2 weeks
Sponsored by:	Netflix
2016-11-25 18:02:43 +00:00
Dimitry Andric
26aa2dc584 Pull in r282174 from upstream llvm trunk (by Krzysztof Parzyszek):
[PPC] Set SP after loading data from stack frame, if no red zone is
  present

  Follow-up to r280705: Make sure that the SP is only restored after
  all data is loaded from the stack frame, if there is no red zone.

  This completes the fix for
  https://llvm.org/bugs/show_bug.cgi?id=26519.

  Differential Revision: https://reviews.llvm.org/D24466

Reported by:    Mark Millard
PR:             214433
2016-11-25 18:01:32 +00:00
Fabien Thomas
cdaf963483 Update r309143 to prevent false sharing.
Reported by:	mjg
Approved by:	so
MFC after:	1 month
2016-11-25 17:20:23 +00:00
Andrew Turner
dc836c65c8 Fix the TLB conflict abort value. This should be a no-op as we don't use
this value in the code.
2016-11-25 16:04:36 +00:00
Fabien Thomas
bf4356266d IPsec RFC6479 support for replay window sizes up to 2^32 - 32 packets.
Since the previous algorithm, based on bit shifting, does not scale
with large replay windows, the algorithm used here is based on
RFC 6479: IPsec Anti-Replay Algorithm without Bit Shifting.
The replay window will be fast to be updated, but will cost as many bits
in RAM as its size.

The previous implementation did not provide a lock on the replay window,
which may lead to replay issues.

Reviewed by:	ae
Obtained from:	emeric.poupon@stormshield.eu
Sponsored by:	Stormshield
Differential Revision:	https://reviews.freebsd.org/D8468
2016-11-25 14:44:49 +00:00
Fabien Thomas
dcf3302859 In a dual processor system (2*6 cores) during IPSec throughput tests,
we see a lot of contention on the arc4 lock, used to generate the IV
of the ESP output packets.

The idea of this patch is to split this mutex in order to reduce the
contention on this lock.

Reviewed by:	delphij, markm, ache
Approved by:	so
Obtained from: emeric.poupon@stormshield.eu
MFC after: 1 month
Sponsored by:	Stormshield
Differential Revision:	https://reviews.freebsd.org/D8130
2016-11-25 13:49:33 +00:00
Ed Maste
0aa5466e7d Add WITH_LLD_AS_LD build knob
If set it installs LLD as /usr/bin/ld.  LLD (as of version 3.9) is not
capable of linking the world and kernel, but can self-host and link many
substantial applications. GNU ld continues to be used for the world and
kernel build, regardless of how this knob is set.

It is on by default for arm64, and off for all other CPU architectures.

Sponsored by:	The FreeBSD Foundation
2016-11-25 13:15:28 +00:00
Sepherosa Ziehau
2641e75742 hyperv/vmbus: Add a simplified version of channel close.
So that the caller can know the channel close error and react accordingly.

MFC after:	1 week
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D8600
2016-11-25 09:13:10 +00:00
Sepherosa Ziehau
892b35bc36 hyperv/vmbus: Propagate close error.
MFC after:	1 week
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D8599
2016-11-25 08:57:52 +00:00
Sepherosa Ziehau
0743140a63 hyperv/vmbus: Always try disconnect/free bufring memory upon channel close
While I'm here, minor wording and style changes.

MFC after:	1 week
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D8598
2016-11-25 08:31:13 +00:00
Sepherosa Ziehau
f2aeeaff6f hyperv/vmbus: Don't free the bufring if its GPADL can't be disconnected.
MFC after:	1 week
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D8570
2016-11-25 07:41:42 +00:00
Sepherosa Ziehau
32ab625a61 hyperv/vmbus: Return EISCONN if the bufring GPADL can't be disconnected.
So that the callers of vmbus_chan_open_br() could handle the passed in
bufring memory properly.

MFC after:	1 week
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D8569
2016-11-25 07:24:11 +00:00
Sepherosa Ziehau
12fbfdab73 hyperv/vmbus: No stranded bufring GPADL is allowed.
MFC after:	1 week
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D8568
2016-11-25 07:03:45 +00:00
Sepherosa Ziehau
11629f1cd6 hyperv/vmbus: GPADL disconnect error on a revoked channel is benign.
MFC after:	1 week
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D8567
2016-11-25 06:48:53 +00:00
Sepherosa Ziehau
fd2b520f2f hyperv/vmbus: Don't close unopened channels.
MFC after:	1 week
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D8566
2016-11-25 06:12:18 +00:00
Sepherosa Ziehau
ba9238f89f hyperv/vmbus: Fix sysctl tree leakage, if channel open fails.
MFC after:	1 week
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D8565
2016-11-25 06:01:45 +00:00
Sepherosa Ziehau
6d147fc18b hyperv/vmbus: Minor style changes.
MFC after:	1 week
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D8564
2016-11-25 05:46:15 +00:00
Sepherosa Ziehau
eb812ea9ab hyperv/vmbus: Commit the GPADL id only after the connection succeeds.
Minor style change.

MFC after:	1 week
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D8563
2016-11-25 05:35:29 +00:00
Dexuan Cui
cdb316ee87 hyperv/vmbus,pcib: unbreak build in case NEW_PCIB is undefined
vmbus_pcib requires NEW_PCIB, but in case that's not defined, we at
least shouldn't break build.

Reviewed by:	sephe
Approved by:	sephe (mentor)
MFC after:	3 days
Sponsored by:	Microsoft
2016-11-25 04:35:40 +00:00
Ed Maste
28a116bab4 Correct lld llvm-tblgen dependency file name 2016-11-25 01:24:35 +00:00
Dimitry Andric
1cf56d672d Upgrade our copies of clang, llvm, lldb, compiler-rt and libc++ to 3.9.0
release, and add lld 3.9.0.  Also completely revamp the build system for
clang, llvm, lldb and their related tools.

Please note that from 3.5.0 onwards, clang, llvm and lldb require C++11
support to build; see UPDATING for more information.

Release notes for llvm, clang and lld are available here:
<http://llvm.org/releases/3.9.0/docs/ReleaseNotes.html>
<http://llvm.org/releases/3.9.0/tools/clang/docs/ReleaseNotes.html>
<http://llvm.org/releases/3.9.0/tools/lld/docs/ReleaseNotes.html>

Thanks to Ed Maste, Bryan Drewery, Andrew Turner, Antoine Brodin and Jan
Beich for their help.

Relnotes:	yes
MFC after:	1 month
2016-11-24 22:54:55 +00:00
Dimitry Andric
1467d043d6 Merge ^/head r309118 through r309122. 2016-11-24 22:33:18 +00:00
Dimitry Andric
7736f1a963 Add UPDATING entry for clang/llvm 3.9.0 import. 2016-11-24 22:18:55 +00:00
Jakub Wojciech Klama
d286418ee6 virtio_console: handle short writes to an Unix domain socket gracefully.
writev() can do a short write.  Retrying it results in a very convoluted
and complex code, so we iterate over iovec and do regular stream_write()
instead.

Approved by:	trasz
Sponsored by:	iXsystems, Inc.
2016-11-24 22:16:18 +00:00
Jakub Wojciech Klama
962094d52a Allow opening virtio-console ports from the host side before guest
enumerates them.

Approved by:	trasz
Sponsored by:	iXsystems, Inc.
2016-11-24 21:53:42 +00:00
Andriy Gapon
18ec6fbc3a virtio_pci: fix announcement of MSI-X interrupts for queues
Queues that do not need interrupts - for instance, output queues - do
not have a corresponding entry in vtpci_msix_vq_interrupts.
So, it was wrong to increment a pointer into that array when iterating
over such a queue.

I ran into this bug while trying to use virtio_console(4) that allocates
a lot of queues with every other being an output queue without an
interrupt handler (if MultiplePorts feature is negotiated).

MFC after:	2 weeks
2016-11-24 21:32:04 +00:00
Dimitry Andric
2000ee7730 Merge ^/head r309106 through r309117. 2016-11-24 21:14:22 +00:00
Dimitry Andric
d590c67486 In preparation for merging back to head, bump __FreeBSD_version,
FREEBSD_CC_VERSION and set date in ObsoleteFiles.inc.
2016-11-24 21:12:43 +00:00
Andriy Gapon
8be1b98cae virtio_console: correctly determine presense of payload and its length
MFC after:	2 weeks
2016-11-24 21:12:32 +00:00
Justin Hibbits
a1748875fc Fix the build post-r309017 for MPC85XX/MPC85XXSPE
r309017 removed two fields from struct vmmeter, which is embedded in struct
pcpu.  This caused the struct size to change, triggering the CTASSERT in
sys/pcpu.h.  Add the extra 8 bytes back in as padding.
2016-11-24 20:31:46 +00:00
Luiz Otavio O Souza
a2c46b941e Add the etherswitch(4) support for TI CPSW.
Adds VLAN and port management abilities for etherswitchcfg(8).

The code is conditionally enabled for now, because it is not necessary on
single ethernet use cases.

Obtained from:	pfSense
MFC after:	2 weeks
Sponsored by:	Rubicon Communications, LLC (Netgate)
2016-11-24 20:14:43 +00:00
Oleksandr Tymoshenko
c5d1ccc2ed [bytgpio] Fix pc98 build by disabling bytgpio module for this platform
Reported by:	dim
2016-11-24 20:08:17 +00:00
Mateusz Guzik
746b6e8176 wait: avoid relocking the child if proc_to_reap returns 1
proc_to_reap would always unlock. However, if it returned 1, kern_wait6
would immediately lock it again. Save the dance.

Reviewed by:	kib
2016-11-24 18:21:48 +00:00
Dag-Erling Smørgrav
4e2825545b Add a warning against modifying this code without understanding it, and
an example of how not to make it more portable.  I've had this lying
around uncommitted since 2009...
2016-11-24 14:50:21 +00:00
Dimitry Andric
0ed76ec8e6 Merge ^/head r308870 through r309105. 2016-11-24 14:39:04 +00:00
Christian Brueffer
9b6cc50d1a Sync the rtwn(4) entry with the manpage. 2016-11-24 10:35:49 +00:00
Andriy Gapon
69bac03666 MFV r308990: 7181 race between zfs_mount and zfs_ioc_rollback
illumos/illumos-gate@90f2c094b3
90f2c094b3

https://www.illumos.org/issues/7181
  zfsvfs_setup() is called in both zfs_mount and zfs_resume_fs paths.
  dmu_objset_set_user(zfsvfs->z_os, zfsvfs) is called early in zfsvfs_setup()
  before the setup is actually completed,
  thus an under-constructed zfsvfs becomes visible.
  Additionally, there is nothing to serialize the two call paths. As a result two
  threads can step on each other's toes.
  assertion failed: zilog->zl_clean_taskq == NULL, file:
  ../../common/fs/zfs/zil.c, line: 1772

  > $c
  vpanic()
  0xfffffffffbdf6928()
  zil_open+0x45(ffffff1bbc5dd000, fffffffff7993880)
  zfsvfs_setup+0x84(ffffffb378d77000, 0)
  zfs_resume_fs+0x132(ffffffb378d77000, ffffffb37ddcf000)
  zfs_ioc_rollback+0x96(ffffffb37ddcf000, ffffff01dcdc4cd0, ffffff01aa091000)
  zfsdev_ioctl+0x215(10a00000000, 5a19, 80465f8, 100003, ffffff01ab318368,
  ffffff0004b59e58)
  cdev_ioctl+0x39(10a00000000, 5a19, 80465f8, 100003, ffffff01ab318368,
  ffffff0004b59e58)
  spec_ioctl+0x60(ffffff0197737700, 5a19, 80465f8, 100003,
  ffffff01ab318368, ffffff0004b59e58)
  fop_ioctl+0x55(ffffff0197737700, 5a19, 80465f8, 100003,
  ffffff01ab318368, ffffff0004b59e58)
  ioctl+0x9b(7, 5a19, 80465f8)
  sys_syscall32+0x1f7()

  > ffffff1bbc5dd000::print objset_t os_zil
  os_zil = 0xffffff1c053cf7c0
  > 0xffffff1c053cf7c0::print zilog_t zl_clean_taskq

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Gordon Ross <gordon.w.ross@gmail.com>
Author: Andriy Gapon <andriy.gapon@clusterhq.com>

MFC after:	2 weeks
2016-11-24 10:34:42 +00:00
Andriy Gapon
b55ae64b50 MFV r308988: 7199, 7200 dsl_dataset_rollback_sync may try to free
already free blocks

7199 dsl_dataset_rollback_sync may try to free already free blocks
7200 no blocks must be born in a txg after a snaphot is created

illumos/illumos-gate@bfaed0b91e
bfaed0b91e

https://www.illumos.org/issues/7199
  dsl_dataset_rollback_sync may try to free already freed blocks when it calls
  dsl_destroy_head_sync_impl to destroy a temporary clone.
  That happens if a snapshot to which we are rolling back and from which the
  clone is created has some ZIL records.

https://www.illumos.org/issues/7200
  No new blocks must be born in a dataset in the same TXG after a snapshot of the
  dataset is taken.
  Those blocks would have the same blk_birth as the dataset's ds_prev_snap_txg
  and as such they would be presumed to belong o the snapshot while in fact they
  do not.
  All the datasets must be clean before sync tasks are run, so the described
  scenario may happen only if one of the sync tasks dirties the dataset and
  another sync task takes its snapshot.
  Then, there will be another sync pass because of the dirty data and the new
  blocks will be born in the same TXG when the data is written out.
  It seems that almost all of the existing sync tasks modify only MOS and do not
  dirty any objsets.
  The only exception that I've been able to identify so far is the rollback which
  can modify an objset when it zeroes out the objset's ZIL.

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Brad Lewis <brad.lewis@delphix.com>
Approved by: Gordon Ross <gordon.w.ross@gmail.com>
Author: Andriy Gapon <andriy.gapon@clusterhq.com>

MFC after:	3 weeks
2016-11-24 10:29:21 +00:00
Andriy Gapon
239c22b73d MFV r308987: 7180 potential race between zfs_suspend_fs+zfs_resume_fs
and zfs_ioc_rename

illumos/illumos-gate@690041b9ca
690041b9ca

https://www.illumos.org/issues/7180
  If a filesystem is not unmounted while the rename is being performed, then, for
  example, a concurrect zfs rollback may call zfs_suspend_fs followed by
  zfs_resume_fs on the same filesystem.
  The latter takes the filesystem's name as an argument. If the filesystem name
  changes as a result of the rename, then dmu_objset_hold(osname, zfsvfs, &os)
  call in zfs_resume_fs would fail resulting in a kernel panic.
  So far I have been able to reproduce this problem on FreeBSD where zfs rename
  has -u option that skips the unmounting before doing the renaming.
  But I think that in theory the same problem can occur on illumos as well,
  because the unmounting is done in userland before invoking the rename ioctl and
  there could be a race with, e.g., zfs mount.
  panic: solaris assert: dmu_objset_hold(osname, zfsvfs, &zfsvfs->z_os) == 0 (0x2
  == 0x0), file: /usr/devel/svn/head/sys/cddl/contrib/opensolaris/uts/common/fs/
  zfs/zfs_vfsops.c, line: 2210
  KDB: stack backtrace:
  db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe004df30710
  vpanic() at vpanic+0x182/frame 0xfffffe004df30790
  panic() at panic+0x43/frame 0xfffffe004df307f0
  assfail3() at assfail3+0x2c/frame 0xfffffe004df30810
  zfs_resume_fs() at zfs_resume_fs+0xb9/frame 0xfffffe004df30860
  zfs_ioc_rollback() at zfs_ioc_rollback+0x61/frame 0xfffffe004df308a0
  zfsdev_ioctl() at zfsdev_ioctl+0x65c/frame 0xfffffe004df30940
  devfs_ioctl_f() at devfs_ioctl_f+0x156/frame 0xfffffe004df309a0
  kern_ioctl() at kern_ioctl+0x246/frame 0xfffffe004df30a00
  sys_ioctl() at sys_ioctl+0x171/frame 0xfffffe004df30ae0
  amd64_syscall() at amd64_syscall+0x2db/frame 0xfffffe004df30bf0
  Xfast_syscall() at Xfast_syscall+0xfb/frame 0xfffffe004df30bf0

Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Approved by: Richard Lowe <richlowe@richlowe.net>

MFC after:	2 weeks
2016-11-24 10:21:22 +00:00
Andriy Gapon
61158a7ce8 MFV r308989: 6428 set canmount=off on unmounted filesystem tries to
unmount children

This is a cosmetic and bookkeeping change as the actual change is
already in FreeBSD.
See r297521, r304520, r308985.
2016-11-24 10:11:09 +00:00
Ganael LAPLANCHE
97a28ad6af Fix path for per-user nsmb.conf file
~/nsmb.conf, as erroneously introduced by r214387, is never used. Fix the man
page to specify that ~/.nsmbrc is used instead.

PR:		210652
Submitted by:	ganael.laplanche@corp.ovh.com
Approved by:	gjb (doceng@)
2016-11-24 10:04:20 +00:00
Andriy Gapon
810f2b5030 firewire: initialize tag label to -1 in fw_xfer_alloc()
Zero can be confused for a potentially valid value.
For example, if I load and unload sbp driver I get a lot of messages
like the following:

fw_tl_free: the xfer is not in the queue (tlabel=0, flag=0x0)
send: dst=0x00 tl=0x00 rt=0 tcode=0x0 pri=0x0 src=0x000
recv: dst=0x01 tl=0x21 rt=1 tcode=0x1 pri=0x0 src=0xffc0
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe04464407e0
fw_tl_free() at fw_tl_free+0x18d/frame 0xfffffe0446440820
fw_xfer_unload() at fw_xfer_unload+0xca/frame 0xfffffe0446440840
fw_xferlist_remove() at fw_xferlist_remove+0x2f/frame 0xfffffe0446440870
sbp_detach() at sbp_detach+0x1e0/frame 0xfffffe04464408e0
device_detach() at device_detach+0x80/frame 0xfffffe0446440900
devclass_driver_deleted() at devclass_driver_deleted+0x6a/frame 0xfffffe0446440940
devclass_delete_driver() at devclass_delete_driver+0x7d/frame 0xfffffe0446440980
driver_module_handler() at driver_module_handler+0xff/frame 0xfffffe04464409d0
module_unload() at module_unload+0x32/frame 0xfffffe04464409f0
linker_file_unload() at linker_file_unload+0x24b/frame 0xfffffe0446440a40
kern_kldunload() at kern_kldunload+0xbc/frame 0xfffffe0446440a70
amd64_syscall() at amd64_syscall+0x314/frame 0xfffffe0446440bf0
Xfast_syscall() at Xfast_syscall+0xfb/frame 0xfffffe0446440bf0

MFC after:	2 weeks
2016-11-24 09:47:56 +00:00
Andriy Gapon
dc6040d671 fwohci: report whether PhysicalUpperBound register is implemented
Please see section 5.15 of 1394 OHCI Specification.
If the register is not implemented, then the physical response unit is
limited to the first 4GB of the physical memory.
In that case the non-cooperative debugging over firewire (using /dev/fwmem)
can not be expected to work if a target has more RAM than that.
The method is described in gdb.4 and the Developer's Handbook.

It seems that most of the consumer hardware does not implement
PhysicalUpperBound register.

MFC after:	1 week
2016-11-24 09:43:42 +00:00
Andriy Gapon
d15b9428bb further fix zfs_lock() diagnostics
It was very wrong to look at the vnode and znode internals without
having locked the vnode first.

Reported by:	pho
Tested by:	pho
MFC after:	1 week
X-MFC with:	r308887
2016-11-24 09:00:51 +00:00
Sepherosa Ziehau
25641fc705 hyperv/hn: Fix primary channel revocation
Since hypervisor will not drain the TX bufring, once the channels are
revoked:
- Setup vmbus orphan handler properly.
- Make sure that suspension will not wait the TX bufring draining
  forever.
- GC the pending TX descs on detach path, before freeing the busdma
  stuffs.

MFC after:	1 week
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D8559
2016-11-24 07:35:16 +00:00
Emmanuel Vadot
24de97b49a Enable the SPI1 and SPI2 node for Olimex A20 SOM EVB.
This was missed in r309079.
2016-11-24 06:43:11 +00:00
Sepherosa Ziehau
91955558f5 hyperv/vmbus: Fix the multi-channel revoking on vmbus side.
- Reference count the sub-channel when channel offer message is
  processed, so that immediate rescind message on the same channel
  will not race sub-channel open on driver side.
- Drop the above reference when sub-channel is closed, this closely
  mimics the hypervisor's reaction when primary channel is closed
  on the VM side.  No drivers use sub-channel after primary channel
  is closed.

MFC after:	1 week
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D8546
2016-11-24 06:01:29 +00:00