sometimes kernel panic when booting ec2 instance

>Description of problem:

Sometimes I get a kernel panic while booting an ec2 instance.
After a couple of minutes the instances reboots en boots without kernel panic.

It does not happen every time.

See kernel panic below

>How reproducible:

Launch ec2 instance with kernel 3.10.0-327.3.1.vz7.10.15.
Check console log.

>Steps to Reproduce:
1. Install vz packages and kernel on Centos7
2. Boot in to vz kernel
3. Check console log

>Actual results:

Kernel panic and stops booting.

>Expected results:

No kernel panic

>Host OS:

Centos7

>Guest OS:

not relevant

>Additional info (see https://openvz.org/Reporting_OpenVZ_problem):

[ 2.281820] ------------[ cut here ]------------
[ 2.282755] kernel BUG at drivers/block/xen-blkfront.c:1711!
[ 2.282755] invalid opcode: 0000 [#1] SMP
[ 2.282755] Modules linked in: ata_generic pata_acpi crct10dif_pclmul crct10dif_common crc32_pclmul crc32c_intel ghash_clmulni_intel xen_netfront(+) xen_blkfront(+) aesni_intel lrw gf128mul glue_helper ablk_helper cryptd ata_piix libata serio_raw floppy sunrpc dm_mirror dm_region_hash dm_log dm_mod scsi_transport_iscsi
[ 2.282755] CPU: 0 PID: 50 Comm: xenwatch ve: 0 Not tainted 3.10.0-327.3.1.vz7.10.15 #1 10.15
[ 2.282755] Hardware name: Xen HVM domU, BIOS 4.2.amazon 12/07/2015
[ 2.282755] task: ffff8800e94e0000 ti: ffff8800e94e8000 task.ti: ffff8800e94e8000
[ 2.282755] RIP: 0010:[<ffffffffa015284f>] [<ffffffffa015284f>] blkfront_setup_indirect+0x41f/0x430 [xen_blkfront]
[ 2.282755] RSP: 0018:ffff8800e94ebcd0 EFLAGS: 00010283
[ 2.282755] RAX: ffff8800351a6e40 RBX: ffff8800e4d732c8 RCX: 0000000000000020
[ 2.282755] RDX: ffff8800351a6e30 RSI: ffff8800e4d732b8 RDI: ffff8800351a6e50
[ 2.282755] RBP: ffff8800e94ebd20 R08: ffff8800351a6e30 R09: ffff8800eb003c00
[ 2.282755] R10: 0000000000000000 R11: ffffffffffffffe8 R12: ffff8800e4d72000
[ 2.282755] R13: ffff8800e4d732b8 R14: 0000000000000020 R15: ffff8800351a6e40
[ 2.282755] FS: 0000000000000000(0000) GS:ffff8800eb600000(0000) knlGS:0000000000000000
[ 2.282755] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 2.282755] CR2: 00007f3cb8232000 CR3: 00000000e27e4000 CR4: 00000000001406f0
[ 2.282755] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 2.282755] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 2.282755] Stack:
[ 2.282755] 0000000000000020 0000000000000001 00000020a0154217 00000100e94ebdbc
[ 2.282755] 00000000409e48eb ffff8800e94ebdbc ffff8800e94de000 ffff8800e4d72000
[ 2.282755] ffff8800e94de040 0000000000000001 ffff8800e94ebe08 ffffffffa0152d4c
[ 2.282755] Call Trace:
[ 2.282755] [<ffffffffa0152d4c>] blkback_changed+0x4ec/0xfc8 [xen_blkfront]
[ 2.282755] [<ffffffff813a99f0>] ? xenbus_gather+0x170/0x190
[ 2.282755] [<ffffffff8162e03d>] ? __slab_free+0x111/0x202
[ 2.282755] [<ffffffff813aaa8d>] xenbus_otherend_changed+0xad/0x110
[ 2.282755] [<ffffffff813a9c77>] ? xenwatch_thread+0x77/0x180
[ 2.282755] [<ffffffff813ac5d3>] backend_changed+0x13/0x20
[ 2.282755] [<ffffffff813a9c66>] xenwatch_thread+0x66/0x180
[ 2.282755] [<ffffffff810a8710>] ? wake_up_atomic_t+0x30/0x30
[ 2.282755] [<ffffffff813a9c00>] ? unregister_xenbus_watch+0x1f0/0x1f0
[ 2.282755] [<ffffffff810a757f>] kthread+0xcf/0xe0
[ 2.282755] [<ffffffff810a74b0>] ? create_kthread+0x60/0x60
[ 2.282755] [<ffffffff81640d98>] ret_from_fork+0x58/0x90
[ 2.282755] [<ffffffff810a74b0>] ? create_kthread+0x60/0x60
[ 2.282755] Code: e1 48 85 c0 75 ce 49 8d 84 24 40 01 00 00 48 89 45 b8 e9 91 fd ff ff 4c 89 ff e8 ad 57 08 e1 e9 f2 fc ff ff 31 c0 e9 2e fe ff ff <0f> 0b e8 4a 8a f2 e0 0f 0b 0f 1f 84 00 00 00 00 00 0f 1f 44 00
[ 2.282755] RIP [<ffffffffa015284f>] blkfront_setup_indirect+0x41f/0x430 [xen_blkfront]
[ 2.282755] RSP <ffff8800e94ebcd0>
[ 2.282755] Tainting kernel with flag 0x7
[ 2.282755] CPU: 0 PID: 50 Comm: xenwatch ve: 0 Not tainted 3.10.0-327.3.1.vz7.10.15 #1 10.15
[ 2.282755] Hardware name: Xen HVM domU, BIOS 4.2.amazon 12/07/2015
[ 2.282755] 0000000000000246 00000000409e48eb ffff8800e94ebaa8 ffffffff816306f6
[ 2.282755] ffff8800e94ebac0 ffffffff8107b131 000000000000000b ffff8800e94ebae8
[ 2.282755] ffffffff81639601 ffff8800e94ebc28 0000000000000246 ffffffff8184cf15
[ 2.282755] Call Trace:
[ 2.282755] [<ffffffff816306f6>] dump_stack+0x19/0x1b
[ 2.282755] [<ffffffff8107b131>] add_taint+0x51/0x60
[ 2.282755] [<ffffffff81639601>] oops_end+0x51/0x150
[ 2.282755] [<ffffffff810184cb>] die+0x4b/0x70
[ 2.282755] [<ffffffff81638d20>] do_trap+0x60/0x170
[ 2.282755] [<ffffffff81015154>] do_invalid_op+0xb4/0x130
[ 2.282755] [<ffffffffa015284f>] ? blkfront_setup_indirect+0x41f/0x430 [xen_blkfront]
[ 2.282755] [<ffffffffa0152532>] ? blkfront_setup_indirect+0x102/0x430 [xen_blkfront]
[ 2.282755] [<ffffffff8164255e>] invalid_op+0x1e/0x30
[ 2.282755] [<ffffffffa015284f>] ? blkfront_setup_indirect+0x41f/0x430 [xen_blkfront]
[ 2.282755] [<ffffffffa0152d4c>] blkback_changed+0x4ec/0xfc8 [xen_blkfront]
[ 2.282755] [<ffffffff813a99f0>] ? xenbus_gather+0x170/0x190
[ 2.282755] [<ffffffff8162e03d>] ? __slab_free+0x111/0x202
[ 2.282755] [<ffffffff813aaa8d>] xenbus_otherend_changed+0xad/0x110
[ 2.282755] [<ffffffff813a9c77>] ? xenwatch_thread+0x77/0x180
[ 2.282755] [<ffffffff813ac5d3>] backend_changed+0x13/0x20
[ 2.282755] [<ffffffff813a9c66>] xenwatch_thread+0x66/0x180
[ 2.282755] [<ffffffff810a8710>] ? wake_up_atomic_t+0x30/0x30
[ 2.282755] [<ffffffff813a9c00>] ? unregister_xenbus_watch+0x1f0/0x1f0
[ 2.282755] [<ffffffff810a757f>] kthread+0xcf/0xe0
[ 2.282755] [<ffffffff810a74b0>] ? create_kthread+0x60/0x60
[ 2.282755] [<ffffffff81640d98>] ret_from_fork+0x58/0x90
[ 2.282755] [<ffffffff810a74b0>] ? create_kthread+0x60/0x60
[ 2.606842] ---[ end trace c0d7030d2d389d42 ]---
[ 2.610246] Kernel panic - not syncing: Fatal exception