Greetings,
i'm getting this crash booting kernel 4.2.1 with
i915.preliminary_hw_support=1.
I'm running an intel skylake i7-6700k cpu on z170 chipset, using xen
(qubes-os).
Full boot log is attached.

[    3.580272] BUG: unable to handle kernel NULL pointer dereference at
0000000000000060
[    3.580286] IP: [<ffffffffa0576d95>] ddi_get_encoder_port+0x5/0x60 [i915]
[    3.580335] PGD 0
[    3.580336] Oops: 0000 [#1] SMP
[    3.580338] Modules linked in: i915(+) nouveau mxm_wmi
crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel radeon
intel_gtt i2c_algo_bit drm_kms_helper ttm drm agpgart wmi vidk
[    3.580347] CPU: 6 PID: 330 Comm: systemd-udevd Not tainted
4.2.3-1.pvops.qubes.x86_64 #1
[    3.580349] Hardware name: To Be Filled By O.E.M. To Be Filled By
O.E.M./Z170 Extreme4, BIOS P2.10 10/14/2015
[    3.580351] task: ffff880867899c00 ti: ffff8808671ac000 task.ti:
ffff8808671ac000
[    3.580353] RIP: e030:[<ffffffffa0576d95>]  [<ffffffffa0576d95>]
ddi_get_encoder_port+0x5/0x60 [i915]
[    3.580367] RSP: e02b:ffff8808671af670  EFLAGS: 00010286
[    3.580369] RAX: 0000000000000000 RBX: 0000000000000000 RCX:
ffff880867576350
[    3.580370] RDX: ffff8808671af6bc RSI: ffff8808671af6c8 RDI:
fffffffffffffff8
[    3.580372] RBP: ffff8808671af708 R08: ffff8808671ac000 R09:
00000000000002e0
[    3.580373] R10: 0000000000007ff0 R11: 0000000000000020 R12:
ffff880867576000
[    3.580375] R13: fffffffffffffff8 R14: 00000000fffb710a R15:
0000000000000001
[    3.580378] FS:  00007f6358f78880(0000) GS:ffff880873580000(0000)
knlGS:ffff880873580000
[    3.580380] CS:  e033 DS: 0000 ES: 0000 CR0: 000000008005003b
[    3.580381] CR2: 0000000000000060 CR3: 00000008670de000 CR4:
0000000000002660
[    3.580383] Stack:
[    3.580384]  ffffffffa057a541 ffff8808671ac000 ffff880865240080
00000000000002e0
[    3.580387]  0000000000000001 0000000000000000 ffffffff8172907a
ffff880867576350
[    3.580389]  ffff880867576000 0000000010000000 00000000005d57f0
ffff8808671af6d8
[    3.580392] Call Trace:
[    3.580404]  [<ffffffffa057a541>] ? intel_prepare_ddi+0x71/0x3c0 [i915]
[    3.580408]  [<ffffffff8172907a>] ? _raw_spin_unlock_irqrestore+0x1a/0x20
[    3.580418]  [<ffffffffa04ff172>] skl_set_power_well+0x362/0x9d0 [i915]
[    3.580427]  [<ffffffffa04ff813>] skl_power_well_enable+0x13/0x20 [i915]
[    3.580435]  [<ffffffffa04ffaa8>] intel_display_power_get+0x98/0xf0
[i915]
[    3.580443]  [<ffffffffa04ffd7b>]
intel_display_set_init_power+0x3b/0x40 [i915]
[    3.580450]  [<ffffffffa04fffed>]
intel_power_domains_init_hw+0x1ed/0x310 [i915]
[    3.580465]  [<ffffffffa059a0d8>] i915_driver_load+0xae8/0xea0 [i915]
[    3.580468]  [<ffffffff81643732>] ?
netlink_broadcast_filtered+0x132/0x3b0
[    3.580471]  [<ffffffff813902e0>] ? kobj_ns_drop+0x50/0x50
[    3.580472]  [<ffffffff8139066c>] ? kobject_uevent_env+0x15c/0x4f0
[    3.580475]  [<ffffffff814bdb2f>] ? devtmpfs_create_node+0x10f/0x140
[    3.580478]  [<ffffffff810e22a1>] ?
__raw_callee_save___pv_queued_spin_unlock+0x11/0x20
[    3.580480]  [<ffffffff8139066c>] ? kobject_uevent_env+0x15c/0x4f0
[    3.580482]  [<ffffffff8171724c>] ? klist_add_tail+0x3c/0x50
[    3.580485]  [<ffffffff814b3db3>] ? device_add+0x233/0x670
[    3.580486]  [<ffffffff810e22a1>] ?
__raw_callee_save___pv_queued_spin_unlock+0x11/0x20
[    3.580488]  [<ffffffff8139066c>] ? kobject_uevent_env+0x15c/0x4f0
[    3.580495]  [<ffffffffa006efdf>] drm_dev_register+0xaf/0x100 [drm]
[    3.580500]  [<ffffffffa0071dbd>] drm_get_pci_dev+0x8d/0x1e0 [drm]
[    3.580509]  [<ffffffffa04ee23b>] i915_pci_probe+0x3b/0x50 [i915]
[    3.580511]  [<ffffffff813d4495>] local_pci_probe+0x45/0xa0
[    3.580513]  [<ffffffff813d5574>] ? pci_match_device+0xf4/0x120
[    3.580515]  [<ffffffff813d56c9>] pci_device_probe+0xe9/0x130
[    3.580518]  [<ffffffff814b7294>] driver_probe_device+0x1f4/0x450
[    3.580520]  [<ffffffff814b7580>] __driver_attach+0x90/0xa0
[    3.580522]  [<ffffffff814b74f0>] ? driver_probe_device+0x450/0x450
[    3.580523]  [<ffffffff814b4e4c>] bus_for_each_dev+0x6c/0xc0
[    3.580525]  [<ffffffff814b6c4e>] driver_attach+0x1e/0x20
[    3.580527]  [<ffffffff814b679b>] bus_add_driver+0x1eb/0x280
[    3.580529]  [<ffffffff814b7f50>] driver_register+0x60/0xe0
[    3.580531]  [<ffffffff813d3d3c>] __pci_register_driver+0x4c/0x50
[    3.580536]  [<ffffffffa0071ff0>] drm_pci_init+0xe0/0x110 [drm]
[    3.580538]  [<ffffffffa0603000>] ? 0xffffffffa0603000
[    3.580546]  [<ffffffffa06030a6>] i915_init+0xa6/0xa8 [i915]
[    3.580549]  [<ffffffff81002141>] do_one_initcall+0xd1/0x200
[    3.580552]  [<ffffffff81197093>] ? free_hot_cold_page+0x113/0x180
[    3.580554]  [<ffffffff811eca26>] ? kmem_cache_alloc_trace+0x196/0x210
[    3.580556]  [<ffffffff81720687>] ? do_init_module+0x28/0x1e8
[    3.580558]  [<ffffffff817206c0>] do_init_module+0x61/0x1e8
[    3.580560]  [<ffffffff81116dd1>] load_module+0x2141/0x25b0
[    3.580563]  [<ffffffff811130e0>] ? __symbol_put+0x60/0x60
[    3.580565]  [<ffffffff8111745f>] SyS_finit_module+0x9f/0xd0
[    3.580567]  [<ffffffff8172962e>] entry_SYSCALL_64_fastpath+0x12/0x71
[    3.580569] Code: 06 00 48 89 df ff d0 41 8b 56 44 83 e0 a0 be 30 cc
06 00 09 c2 48 8b 83 c8 00 00 00 e9 74 fd ff ff 0f 1f 44 00 00 0f 1f 44
00 00 <8b> 47 68 83 f8 0b 74 2c 83 f8 0a 74 1
[    3.580587] RIP  [<ffffffffa0576d95>] ddi_get_encoder_port+0x5/0x60
[i915]
[    3.580601]  RSP <ffff8808671af670>
[    3.580602] CR2: 0000000000000060
[    3.580604] ---[ end trace 190ed1318b631935 ]---

John.