Guest kernel crashes with GPF on volume attach

This isn't really a bug in nova, but it's something that we're hitting in CI quite a bit, so I'm filing here to record the details and so I can recheck against it. The actual bug is either in the guest (cirros 0.5.2) kernel, QEMU, or something similar. In tests where we attach a volume to a running guest, we occasionally get a guest kernel crash and stack trace that pretty much prevents anything else from working later in the test.

Here's what the trace looks like:

[ 10.152160] virtio_blk virtio2: [vda] 2093056 512-byte logical blocks (1.07 GB/1022 MiB)
[ 10.198313] GPT:Primary header thinks Alt. header is not at the end of the disk.
[ 10.199033] GPT:229375 != 2093055
[ 10.199278] GPT:Alternate GPT header not at the end of the disk.
[ 10.199632] GPT:229375 != 2093055
[ 10.199857] GPT: Use GNU Parted to correct GPT errors.
[ 11.291631] random: fast init done
[ 11.312007] random: crng init done
[ 11.419215] general protection fault: 0000 [#1] SMP PTI
[ 11.420843] CPU: 0 PID: 199 Comm: modprobe Not tainted 5.3.0-26-generic #28~18.04.1-Ubuntu
[ 11.421917] Hardware name: OpenStack Foundation OpenStack Nova, BIOS 1.13.0-1ubuntu1.1 04/01/2014
[ 11.424732] RIP: 0010:__kmalloc_track_caller+0xa1/0x250
[ 11.425934] Code: 65 49 8b 50 08 65 4c 03 05 b4 48 37 6f 4d 8b 38 4d 85 ff 0f 84 77 01 00 00 41 8b 59 20 49 8b 39 48 8d 4a 01 4c 89 f8 4c 01 fb <48> 33 1b 49 33 99 70 01 00 00 65 48 0f c7 0f 0f 94 c0 84 c0 74 bd
[ 11.428460] RSP: 0018:ffffb524801afaf0 EFLAGS: 00000206
[ 11.429261] RAX: 51f2a72f63305b11 RBX: 51f2a72f63305b11 RCX: 0000000000002b7e
[ 11.430205] RDX: 0000000000002b7d RSI: 0000000000000cc0 RDI: 000000000002f040
[ 11.431123] RBP: ffffb524801afb28 R08: ffff90480762f040 R09: ffff904807001c40
[ 11.432032] R10: ffffb524801afc28 R11: 0000000000000001 R12: 0000000000000cc0
[ 11.432953] R13: 0000000000000004 R14: ffff904807001c40 R15: 51f2a72f63305b11
[ 11.434125] FS: 00007fb31d2486a0(0000) GS:ffff904807600000(0000) knlGS:0000000000000000
[ 11.435139] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 11.435909] CR2: 0000000000abf9a8 CR3: 00000000027c2000 CR4: 00000000000006f0
[ 11.437208] Call Trace:
[ 11.438716] ? kstrdup_const+0x24/0x30
[ 11.439170] kstrdup+0x31/0x60
[ 11.439668] kstrdup_const+0x24/0x30
[ 11.440036] kvasprintf_const+0x86/0xa0
[ 11.440397] kobject_set_name_vargs+0x23/0x90
[ 11.440791] kobject_set_name+0x49/0x70
[ 11.452382] bus_register+0x80/0x270
[ 11.462448] ? 0xffffffffc033b000
[ 11.471469] hid_init+0x2b/0x62 [hid]
[ 11.480198] do_one_initcall+0x4a/0x1fa
[ 11.487738] ? _cond_resched+0x19/0x40
[ 11.495227] ? kmem_cache_alloc_trace+0x1ff/0x210
[ 11.502700] do_init_module+0x5f/0x227
[ 11.510944] load_module+0x1b96/0x2140
[ 11.517993] __do_sys_finit_module+0xfc/0x120
[ 11.525101] ? __do_sys_finit_module+0xfc/0x120
[ 11.533182] __x64_sys_finit_module+0x1a/0x20
[ 11.542123] do_syscall_64+0x5a/0x130
[ 11.549183] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 11.557921] RIP: 0033:0x7fb31cbaba7d
[ 11.565182] Code: 48 89 57 30 48 8b 04 24 48 89 47 38 e9 79 9e 02 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 3a fd ff ff c3 48 c7 c6 01 00 00 00 e9 a1
[ 11.581697] RSP: 002b:00007ffdf6793c18 EFLAGS: 00000206 ORIG_RAX: 0000000000000139
[ 11.589245] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fb31cbaba7d
[ 11.597913] RDX: 0000000000000000 RSI: 00000000004ab235 RDI: 0000000000000003
[ 11.605694] RBP: 00000000004ab235 R08: 00000000000000c7 R09: 00007fb31cbeba5f
[ 11.613566] R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000003
[ 11.620772] R13: 0000000000ab3c70 R14: 0000000000ab3cc0 R15: 0000000000000000
[ 11.628586] Modules linked in: hid(+) virtio_rng virtio_gpu drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm virtio_scsi virtio_net net_failover failover virtio_input virtio_blk qemu_fw_cfg 9pnet_virtio 9pnet pcnet32 8139cp mii ne2k_pci 8390 e1000
[ 11.654944] ---[ end trace 9a9e8eebda38a127 ]---
[ 11.663441] RIP: 0010:__kmalloc_track_caller+0xa1/0x250
[ 11.671942] Code: 65 49 8b 50 08 65 4c 03 05 b4 48 37 6f 4d 8b 38 4d 85 ff 0f 84 77 01 00 00 41 8b 59 20 49 8b 39 48 8d 4a 01 4c 89 f8 4c 01 fb <48> 33 1b 49 33 99 70 01 00 00 65 48 0f c7 0f 0f 94 c0 84 c0 74 bd
[ 11.689167] RSP: 0018:ffffb524801afaf0 EFLAGS: 00000206
[ 11.698903] RAX: 51f2a72f63305b11 RBX: 51f2a72f63305b11 RCX: 0000000000002b7e
[ 11.707107] RDX: 0000000000002b7d RSI: 0000000000000cc0 RDI: 000000000002f040
[ 11.715748] RBP: ffffb524801afb28 R08: ffff90480762f040 R09: ffff904807001c40
[ 11.724372] R10: ffffb524801afc28 R11: 0000000000000001 R12: 0000000000000cc0
[ 11.735147] R13: 0000000000000004 R14: ffff904807001c40 R15: 51f2a72f63305b11
[ 11.747065] FS: 00007fb31d2486a0(0000) GS:ffff904807600000(0000) knlGS:0000000000000000
[ 11.755136] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 11.763985] CR2: 0000000000abf9a8 CR3: 00000000027c2000 CR4: 00000000000006f0
Segmentation fault