Just rebooted with tunable again, and no loading. On bootup on the console it says "Loading Kernel Modules:" but then has nothing after it. Here's the output of various commands. Maybe I have top put xhci.ko as the name?
[root@ned ~]# kldstat
Id Refs Address Size Name
1 65 0xffffffff80200000 1468380 kernel
2 1 0xffffffff81812000 4845 geom_stripe.ko
3 1 0xffffffff81817000 10489 geom_raid3.ko
4 1 0xffffffff81828000 efdd geom_raid5.ko
5 1 0xffffffff81837000 5806 geom_gate.ko
6 1 0xffffffff8183d000 49bd geom_multipath.ko
7 1 0xffffffff81842000 15ff44 zfs.ko
8 14 0xffffffff819a2000 5701 opensolaris.ko
9 1 0xffffffff819a8000 b56 dtraceall.ko
10 1 0xffffffff819a9000 4ea3 profile.ko
11 3 0xffffffff819ae000 3569 cyclic.ko
12 11 0xffffffff819b2000 3433a dtrace.ko
13 1 0xffffffff819e7000 fb24 systrace_freebsd32.ko
14 1 0xffffffff819f7000 1098d systrace.ko
15 1 0xffffffff81a08000 4bca sdt.ko
16 1 0xffffffff81a0d000 48f5 lockstat.ko
17 1 0xffffffff81a12000 a9cc fasttrap.ko
18 1 0xffffffff81a1d000 6663 fbt.ko
19 1 0xffffffff81a24000 557d dtnfscl.ko
20 1 0xffffffff81a2a000 4585 dtmalloc.ko
21 1 0xffffffff81a2f000 4488 dtio.ko
22 1 0xffffffff81a34000 30fc5 if_cxgbe.ko
23 2 0xffffffff81a65000 2bb1 vboxnetflt.ko
24 2 0xffffffff81a68000 361ff vboxdrv.ko
25 1 0xffffffff81a9f000 447f ng_ether.ko
26 1 0xffffffff81aa4000 400a vboxnetadp.ko
[root@ned ~]# usbconfig
ugen0.1: <EHCI root HUB Intel> at usbus0, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=SAVE (0mA)
ugen1.1: <EHCI root HUB Intel> at usbus1, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=SAVE (0mA)
ugen0.2: <product 0x0024 vendor 0x8087> at usbus0, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=SAVE (0mA)
ugen1.2: <product 0x0024 vendor 0x8087> at usbus1, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=SAVE (0mA)
ugen0.3: <Hermon USB hidmouse Device Winbond Electronics Corp> at usbus0, cfg=0 md=HOST spd=FULL (12Mbps) pwr=ON (100mA)
ugen0.4: <product 0x1000 vendor 0x090c> at usbus0, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=ON (500mA)
[root@ned ~]# kldload xhci
[root@ned ~]# kldstat
Id Refs Address Size Name
1 68 0xffffffff80200000 1468380 kernel
2 1 0xffffffff81812000 4845 geom_stripe.ko
3 1 0xffffffff81817000 10489 geom_raid3.ko
4 1 0xffffffff81828000 efdd geom_raid5.ko
5 1 0xffffffff81837000 5806 geom_gate.ko
6 1 0xffffffff8183d000 49bd geom_multipath.ko
7 1 0xffffffff81842000 15ff44 zfs.ko
8 14 0xffffffff819a2000 5701 opensolaris.ko
9 1 0xffffffff819a8000 b56 dtraceall.ko
10 1 0xffffffff819a9000 4ea3 profile.ko
11 3 0xffffffff819ae000 3569 cyclic.ko
12 11 0xffffffff819b2000 3433a dtrace.ko
13 1 0xffffffff819e7000 fb24 systrace_freebsd32.ko
14 1 0xffffffff819f7000 1098d systrace.ko
15 1 0xffffffff81a08000 4bca sdt.ko
16 1 0xffffffff81a0d000 48f5 lockstat.ko
17 1 0xffffffff81a12000 a9cc fasttrap.ko
18 1 0xffffffff81a1d000 6663 fbt.ko
19 1 0xffffffff81a24000 557d dtnfscl.ko
20 1 0xffffffff81a2a000 4585 dtmalloc.ko
21 1 0xffffffff81a2f000 4488 dtio.ko
22 1 0xffffffff81a34000 30fc5 if_cxgbe.ko
23 2 0xffffffff81a65000 2bb1 vboxnetflt.ko
24 2 0xffffffff81a68000 361ff vboxdrv.ko
25 1 0xffffffff81a9f000 447f ng_ether.ko
26 1 0xffffffff81aa4000 400a vboxnetadp.ko
27 1 0xffffffff81aa9000 b69e xhci.ko
[root@ned ~]# usbconfig
ugen0.1: <EHCI root HUB Intel> at usbus0, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=SAVE (0mA)
ugen1.1: <EHCI root HUB Intel> at usbus1, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=SAVE (0mA)
ugen0.2: <product 0x0024 vendor 0x8087> at usbus0, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=SAVE (0mA)
ugen1.2: <product 0x0024 vendor 0x8087> at usbus1, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=SAVE (0mA)
ugen0.3: <Hermon USB hidmouse Device Winbond Electronics Corp> at usbus0, cfg=0 md=HOST spd=FULL (12Mbps) pwr=ON (100mA)
ugen0.4: <product 0x1000 vendor 0x090c> at usbus0, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=ON (500mA)
ugen2.1: <XHCI root HUB 0x1912> at usbus2, cfg=0 md=HOST spd=SUPER (5.0Gbps) pwr=SAVE (0mA)