I'm getting the following with 2.6.30-rc5-00096-ga4d7749:

[   16.433725] parport_pc 00:0a: reported by Plug and Play ACPI
[   16.433845] parport0: PC-style at 0x378 (0x778), irq 7, dma 1 [PCSPP,TRISTATE,COMPAT,ECP,DMA]
[   16.434699] BUG: unable to handle kernel NULL pointer dereference at 00000000000000d8
[   16.434816] IP: [<ffffffff811f9937>] get_domain_for_dev+0x57/0x6a0
[   16.434896] PGD 11892e067 PUD 118cd0067 PMD 0 
[   16.435031] Oops: 0000 [#1] SMP 
[   16.435133] last sysfs file: /sys/module/parport/initstate
[   16.435181] CPU 1 
[   16.435251] Modules linked in: parport_pc(+) parport dell_laptop dcdbas intel_agp serio_raw evdev usbhid hid ehci_hcd uhci_hcd pata_acpi ide_pci_generic
[   16.435718] Pid: 1774, comm: modprobe Not tainted 2.6.30-rc5-dmar-00096-ga4d7749 #58 Latitude E4300                  
[   16.435781] RIP: 0010:[<ffffffff811f9937>]  [<ffffffff811f9937>] get_domain_for_dev+0x57/0x6a0
[   16.435870] RSP: 0018:ffff8801184cdaf8  EFLAGS: 00010246
[   16.435916] RAX: 0000000000000000 RBX: ffff88011a6e2380 RCX: 0000000000000000
[   16.435964] RDX: 0000000000001000 RSI: 0000000000000030 RDI: ffff88011a6e2380
[   16.436012] RBP: ffff8801184cdb78 R08: 0000000000ffffff R09: ffff8801194a0000
[   16.436075] R10: 0000000000000000 R11: 00000000000000a4 R12: 0000000000001000
[   16.436123] R13: 0000000000000030 R14: ffff88011a6e2380 R15: 0000000000000000
[   16.436172] FS:  00007fbbf8a176f0(0000) GS:ffff880028038000(0000) knlGS:0000000000000000
[   16.436231] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[   16.436277] CR2: 00000000000000d8 CR3: 0000000118cda000 CR4: 00000000000006e0
[   16.436324] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   16.436372] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[   16.436420] Process modprobe (pid: 1774, threadinfo ffff8801184cc000, task ffff8801188fd980)
[   16.436479] Stack:
[   16.436519]  0000000000000246 ffffffff81644ec0 0000004000000000 ffffffff81644a80
[   16.436651]  ffffffff81644a80 ffff88011a6e2400 ffff8801188fd980 0000000000001000
[   16.436850]  0000000000000000 ffff88011a6e2400 ffff8801184cdbe8 ffff88011a6e2380
[   16.437005] Call Trace:
[   16.437005]  [<ffffffff811fa51e>] get_valid_domain_for_dev+0x1e/0x90
[   16.437005]  [<ffffffff811fa8b4>] __intel_map_single+0x44/0x170
[   16.437005]  [<ffffffff811faab2>] intel_alloc_coherent+0x92/0xd0
[   16.437005]  [<ffffffffa00734cd>] parport_pc_probe_port+0x8cd/0xfb0 [parport_pc]
[   16.437005]  [<ffffffffa0073d3e>] parport_pc_pnp_probe+0x18e/0x230 [parport_pc]
[   16.437005]  [<ffffffff8123ea24>] pnp_device_probe+0xa4/0x120
[   16.437005]  [<ffffffff81275541>] driver_probe_device+0xb1/0x2b0
[   16.437005]  [<ffffffff812757d3>] __driver_attach+0x93/0xa0
[   16.437005]  [<ffffffff81275740>] ? __driver_attach+0x0/0xa0
[   16.437005]  [<ffffffff81274bfb>] bus_for_each_dev+0x6b/0xa0
[   16.437005]  [<ffffffff812752ec>] driver_attach+0x1c/0x20
[   16.437005]  [<ffffffff81274375>] bus_add_driver+0x1a5/0x2e0
[   16.437005]  [<ffffffff81275aa9>] driver_register+0x79/0x160
[   16.437005]  [<ffffffff8123e7cc>] pnp_register_driver+0x1c/0x20
[   16.437005]  [<ffffffffa0050448>] parport_pc_init+0x39c/0x3b3 [parport_pc]
[   16.437005]  [<ffffffffa00500ac>] ? parport_pc_init+0x0/0x3b3 [parport_pc]
[   16.437005]  [<ffffffff8100904c>] do_one_initcall+0x3c/0x170
[   16.437005]  [<ffffffff8105ecf3>] ? __blocking_notifier_call_chain+0x63/0x80
[   16.437005]  [<ffffffff8107061d>] sys_init_module+0xad/0x200
[   16.437005]  [<ffffffff8100bf2b>] system_call_fastpath+0x16/0x1b
[   16.437005] Code: 74 22 4c 8b 60 30 4d 85 e4 74 19 4c 89 e0 48 8b 5d d8 4c 8b 65 e0 4c 8b 6d e8 4c 8b 75 f0 4c 8b 7d f8 c9 c3 49 8b 46 10 4c 89 f7 <48> 8b 80 d8 00 00 00 44 8b 38 e8 8a 52 ff ff 48 89 45 90 48 85 
[   16.437005] RIP  [<ffffffff811f9937>] get_domain_for_dev+0x57/0x6a0
[   16.437005]  RSP <ffff8801184cdaf8>
[   16.437005] CR2: 00000000000000d8
[   16.440745] ---[ end trace 9244fcdcb95e3383 ]---

and then a little later, another oops while loading dcdbas:

[   23.717004]  [<ffffffff811fa51e>] get_valid_domain_for_dev+0x1e/0x90
[   23.717004]  [<ffffffff811fa8b4>] __intel_map_single+0x44/0x170
[   23.717004]  [<ffffffff811faab2>] intel_alloc_coherent+0x92/0xd0
[   23.717004]  [<ffffffffa00606db>] smi_data_buf_realloc+0xcb/0x220 [dcdbas]
[   23.717004]  [<ffffffffa00608da>] smi_data_buf_size_store+0x3a/0x60 [dcdbas]
[   23.717004]  [<ffffffff81270fcb>] dev_attr_store+0x1b/0x20
[   23.717004]  [<ffffffff8113a7f5>] sysfs_write_file+0xc5/0x140
[   23.717004]  [<ffffffff810dea4b>] vfs_write+0xcb/0x190
[   23.717004]  [<ffffffff810dec00>] sys_write+0x50/0x90
[   23.717004]  [<ffffffff8100bf2b>] system_call_fastpath+0x16/0x1b

Hardware is a Dell E4300, BIOS A05, with a docking station (that
includes parport) attached.  I don't see the parport oops when booted
without the docking station, but the dcdbas oops is still present.

I've attached the complete dmesg; more debug info is available at
http://web.hexapodia.org/~adi/sysinfo/1242072617_cvpe4300_2.6.30-rc5-dmar-00096-ga4d7749/

-andy