Hi Paolo,

We noticed the below kernel BUG on

git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

commit 93c4adc7afedf9b0ec190066d45b6d67db5270da
Author:     Paolo Bonzini <pbonzini@redhat.com>
AuthorDate: Wed Mar 5 23:19:52 2014 +0100
Commit:     Paolo Bonzini <pbonzini@redhat.com>
CommitDate: Mon Mar 17 12:21:39 2014 +0100

      KVM: x86: handle missing MPX in nested virtualization

[   15.785160] BUG: unable to handle kernel NULL pointer dereference at 00000000000002b0
[   15.794972] IP: [<ffffffff81017fc9>] kvm_arch_init+0x110/0x22f
[   15.802077] PGD 0
[   15.804890] Oops: 0000 [#1] SMP
[   15.809153] Modules linked in:
[   15.813132] CPU: 12 PID: 1 Comm: swapper/0 Not tainted 3.14.0-rc7-03441-gad1b51f #1
[   15.822566] Hardware name: Intel Corporation S2600CP/S2600CP, BIOS RMLSDP.86I.R2.28.D690.1306271008 06/27/2013
[   15.834635] task: ffff880813da8000 ti: ffff880813db0000 task.ti: ffff880813db0000
[   15.843883] RIP: 0010:[<ffffffff81017fc9>]  [<ffffffff81017fc9>] kvm_arch_init+0x110/0x22f
[   15.854097] RSP: 0000:ffff880813db1df0  EFLAGS: 00010246
[   15.860514] RAX: 0000000000000000 RBX: 000000000000000c RCX: 0000000000000000
[   15.868973] RDX: 0000000000000000 RSI: ffff880813db1dfc RDI: 0000000000000d90
[   15.877436] RBP: ffff880813db1e28 R08: 0000000000015f40 R09: ffff88081f003e00
[   15.885895] R10: ffffffff811bd5ec R11: 0000000000000000 R12: 0000000000000017
[   15.894353] R13: 0000000000000018 R14: ffff880813db1dfc R15: ffffffff82218f20
[   15.902813] FS:  0000000000000000(0000) GS:ffff88101ee40000(0000) knlGS:0000000000000000
[   15.922590] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   15.929492] CR2: 00000000000002b0 CR3: 000000000220f000 CR4: 00000000001407e0
[   15.937957] Stack:
[   15.940680]  0000000013db1e10 00000000811f0f59 0000000000000006 ffffffff8236743a
[   15.950159]  0000000000000040 0000000000003f40 0000000000000000 ffff880813db1e68
[   15.959665]  ffffffff81003d72 ffffffff8236743a 0000000000000006 ffffffff8236743a
[   15.969172] Call Trace:
[   15.972399]  [<ffffffff8236743a>] ? vmx_check_processor_compat+0x61/0x61
[   15.980376]  [<ffffffff81003d72>] kvm_init+0x24/0x27b
[   15.986504]  [<ffffffff8236743a>] ? vmx_check_processor_compat+0x61/0x61
[   15.994478]  [<ffffffff8236743a>] ? vmx_check_processor_compat+0x61/0x61
[   16.002452]  [<ffffffff82367729>] vmx_init+0x2ef/0x579
[   16.008675]  [<ffffffff8236743a>] ? vmx_check_processor_compat+0x61/0x61
[   16.016648]  [<ffffffff81000309>] do_one_initcall+0xd1/0x175
[   16.023462]  [<ffffffff8110f5d2>] ? parse_args+0x20a/0x3bf
[   16.030083]  [<ffffffff823620ca>] kernel_init_freeable+0x1a6/0x22b
[   16.037477]  [<ffffffff823618bc>] ? do_early_param+0x88/0x88
[   16.044287]  [<ffffffff81ae99c9>] ? rest_init+0x89/0x89
[   16.050612]  [<ffffffff81ae99d7>] kernel_init+0xe/0xdf
[   16.056839]  [<ffffffff81b07b7c>] ret_from_fork+0x7c/0xb0
[   16.063355]  [<ffffffff81ae99c9>] ? rest_init+0x89/0x89
[   16.069676] Code: 3c 9d 10 6a 21 82 4c 89 f6 e8 89 ef 05 00 66 90 8b 45 d4 85 c0 78 da 81 3c 9d 10 6a 21 82 90 0d 00 00 75 b3 48 8b 05 87 91 4a 01 <ff> 90 b0 02 00 00 84 c0 75 a2 48 83 c3 01 48 83 fb 0d 75 bc 45
[   16.097850] RIP  [<ffffffff81017fc9>] kvm_arch_init+0x110/0x22f
[   16.105043]  RSP <ffff880813db1df0>
[   16.109417] CR2: 00000000000002b0
[   16.113611] ---[ end trace 740886b77a583740 ]---
[   16.119251] Kernel panic - not syncing: Fatal exception

Full dmesg & Kconifg are attached, and more details can be provided on your request.

BTW, same issue has been reported by Fengguang last month.

https://lkml.org/lkml/2014/3/26/200

Thanks,
Jet