FYI, we noticed the below changes on

https://github.com/jiangliu/linux.git irqdomain/p2v7
commit 515b463a5a4c2bac0593c6d88a475a32d65f4bcc ("x86, PCI, MSI: Use hierarchy irqdomain to manage MSI interrupts")


+------------------------------------------+------------+------------+
|                                          | dadb7cd295 | 515b463a5a |
+------------------------------------------+------------+------------+
| boot_successes                           | 6          | 1          |
| early-boot-hang                          | 1          |            |
| boot_failures                            | 0          | 4          |
| BUG:unable_to_handle_kernel              | 0          | 4          |
| Oops                                     | 0          | 4          |
| RIP:init_irq_alloc_info                  | 0          | 4          |
| Kernel_panic-not_syncing:Fatal_exception | 0          | 4          |
| backtrace:init_irq_alloc_info            | 0          | 4          |
| backtrace:vp_find_vqs                    | 0          | 4          |
| backtrace:init_vq                        | 0          | 4          |
| backtrace:init                           | 0          | 4          |
| backtrace:kernel_init_freeable           | 0          | 4          |
+------------------------------------------+------------+------------+


[   20.962013] BUG: unable to handle kernel NULL pointer dereference at 0000000000000002
[   20.964023] IP: [<ffffffff81074795>] init_irq_alloc_info+0x13/0x1b
[   20.964023] PGD 0 
[   20.964023] Oops: 0002 [#1] SMP DEBUG_PAGEALLOC
[   20.964023] Modules linked in:
[   20.964023] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.18.0-rc4-g4ae16b6 #1457
[   20.964023] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   20.964023] task: ffff8801289c0010 ti: ffff8801289c4000 task.ti: ffff8801289c4000
[   20.964023] RIP: 0010:[<ffffffff81074795>]  [<ffffffff81074795>] init_irq_alloc_info+0x13/0x1b
[   20.964023] RSP: 0000:ffff8801289c7928  EFLAGS: 00010246
[   20.964023] RAX: 0000000000000000 RBX: 0000000000000002 RCX: 000000000000000a
[   20.964023] RDX: 0000000000000002 RSI: 0000000000000000 RDI: 0000000000000002
[   20.964023] RBP: ffff8801289c7928 R08: 0000000000000008 R09: 0000000000000000
[   20.964023] R10: ffff8800b8399f80 R11: 0000000000000023 R12: ffff8800db055000
[   20.964023] R13: ffff8800d1ee8f98 R14: ffff880129cc3f80 R15: ffffffff83e36800
[   20.964023] FS:  0000000000000000(0000) GS:ffff88012a200000(0000) knlGS:0000000000000000
[   20.964023] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[   20.964023] CR2: 0000000000000002 CR3: 0000000003e1a000 CR4: 00000000000006f0
[   20.964023] Stack:
[   20.964023]  ffff8801289c7958 ffffffff810770be ffff8801289c7980 0000000000000002
[   20.964023]  ffffffff83e36840 ffff8800db055098 ffff8801289c79d8 ffffffff8110fd29
[   20.964023]  0000000000000000 0000000000000000 ffff8800db055000 0000000000000011
[   20.964023] Call Trace:
[   20.964023]  [<ffffffff810770be>] pci_msi_prepare+0x2d/0x54
[   20.964023]  [<ffffffff8110fd29>] msi_domain_alloc_irqs+0x4a/0x162
[   20.964023]  [<ffffffff8285063a>] ? dmar_find_matched_drhd_unit+0xf7/0x10b
[   20.964023]  [<ffffffff8177e2ee>] pci_msi_domain_alloc_irqs+0x15/0x17
[   20.964023]  [<ffffffff8107727c>] native_setup_msi_irqs+0x61/0x6c
[   20.964023]  [<ffffffff8104f786>] arch_setup_msi_irqs+0xf/0x11
[   20.964023]  [<ffffffff8177d3e0>] pci_msi_setup_msi_irqs+0x45/0x4c
[   20.964023]  [<ffffffff8177daf7>] pci_enable_msix+0x1d8/0x2d0
[   20.964023]  [<ffffffff8177dc20>] pci_enable_msix_range+0x31/0x50
[   20.964023]  [<ffffffff8185dfa6>] vp_request_msix_vectors+0xb6/0x1f8
[   20.964023]  [<ffffffff8185e196>] vp_try_to_find_vqs+0xae/0x43e
[   20.964023]  [<ffffffff8172fbc5>] ? vsnprintf+0x374/0x3ad
[   20.964023]  [<ffffffff8185e558>] vp_find_vqs+0x32/0x8d
[   20.964023]  [<ffffffff81b416aa>] init_vq+0x14f/0x1f8
[   20.964023]  [<ffffffff81b41896>] virtblk_probe+0xf3/0x501
[   20.964023]  [<ffffffff81238727>] ? sysfs_do_create_link_sd+0x78/0xa8
[   20.964023]  [<ffffffff8185dba0>] ? vp_set_status+0x25/0x27
[   20.964023]  [<ffffffff8185c2ec>] virtio_dev_probe+0xbd/0x104
[   20.964023]  [<ffffffff81b09a19>] driver_probe_device+0xb0/0x1d7
[   20.964023]  [<ffffffff81b09bdf>] __driver_attach+0x62/0x85
[   20.964023]  [<ffffffff81b09b7d>] ? __device_attach+0x3d/0x3d
[   20.964023]  [<ffffffff81b08009>] bus_for_each_dev+0x6f/0x89
[   20.964023]  [<ffffffff81b0957d>] driver_attach+0x1e/0x20
[   20.964023]  [<ffffffff81b09229>] bus_add_driver+0x110/0x1cf
[   20.964023]  [<ffffffff84452673>] ? nbd_init+0x39c/0x39c
[   20.964023]  [<ffffffff81b0a235>] driver_register+0x8f/0xcc
[   20.964023]  [<ffffffff84452673>] ? nbd_init+0x39c/0x39c
[   20.964023]  [<ffffffff8185c5fd>] register_virtio_driver+0x2b/0x2d
[   20.964023]  [<ffffffff844526d0>] init+0x5d/0x8b
[   20.964023]  [<ffffffff8100216d>] do_one_initcall+0xee/0x17e
[   20.964023]  [<ffffffff843e60ef>] kernel_init_freeable+0x1ec/0x274
[   20.964023]  [<ffffffff82d3c238>] ? rest_init+0xcc/0xcc
[   20.964023]  [<ffffffff82d3c246>] kernel_init+0xe/0xdf
[   20.964023]  [<ffffffff82d719fc>] ret_from_fork+0x7c/0xb0
[   20.964023]  [<ffffffff82d3c238>] ? rest_init+0xcc/0xcc
[   20.964023] Code: eb 05 bb da ff ff ff 48 83 c4 28 89 d8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 0f 1f 44 00 00 55 48 89 fa b9 0a 00 00 00 31 c0 48 89 e5 <f3> ab 5d 48 89 72 08 c3 0f 1f 44 00 00 55 48 85 f6 b9 0a 00 00 
[   20.964023] RIP  [<ffffffff81074795>] init_irq_alloc_info+0x13/0x1b
[   20.964023]  RSP <ffff8801289c7928>
[   20.964023] CR2: 0000000000000002
[   20.964023] ---[ end trace 21200aca189fb8f5 ]---
[   20.964023] Kernel panic - not syncing: Fatal exception
[   20.964023] Kernel Offset: 0x0 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffff9fffffff)




	--yliu