On 7/1/17 13:35 , Ján Poctavek wrote:
> Hi,
> 
> I'm trying to get a KVM/qemu live migration working on SmartOS. My
> starting point was the same problem as in this post:
> https://www.listbox.com/member/archive/184463/2012/04/sort/time_rev/page/2/entry/24:101/20120417112635:B4169A4C-88A1-11E1-9C88-F96B3BAD9C1B/
> 
> 
> I have dtraced the EIVALs and I have identified two problems -
> unimplemented ioctls: KVM_GET_IRQCHIP and KVM_GET_CLOCK.
> 
> The first one can be (at least temporarily) solved by adding
> "-no-kvm-irqchip" to qemu flags.
> 
> With the second one, I have implemented ioctl calls for KVM_GET_CLOCK
> and KVM_SET_CLOCK in the KVM kernel module.
> 
> After this, I am able to do migration without qemu complaining. More
> importantly, I am able to successfully migrate the VM in GRUB prompt
> (using "migrate" qemu command).
> 
> But when migrating linux (booted into the initrd target for simplicity),
> it panicks after pressing "enter" in the console:
> 
> [   28.337953] double fault: 0000 [#1] SMP
> [   28.337953] Modules linked in: ext4 mbcache jbd2 sd_mod crc_t10dif
> sr_mod cdrom crct10dif_generic crct10dif_common ata_generic pata_acpi
> ata_piix serio_raw libata floppy
> [   28.337953] CPU: 0 PID: 195 Comm: sh Not tainted
> 3.10.0-514.16.1.el7.x86_64 #1
> [   28.337953] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
> [   28.337953] task: ffff88001f460000 ti: ffff88001f74c000 task.ti:
> ffff88001f74c000
> [   28.337953] RIP: 0010:[<ffffffff8169294b>] [<ffffffff8169294b>]
> do_page_fault+0xb/0x90
> [   28.337953] RSP: 0008:00007ffc606b9000  EFLAGS: 00010097
> [   28.337953] RAX: 000000008168e8ec RBX: 0000000000000001 RCX:
> ffffffff8168e8ec
> [   28.337953] RDX: 000000000000cdc0 RSI: 0000000000000000 RDI:
> 00007ffc606b9018
> [   28.337953] RBP: 00007ffc606b9008 R08: 000000000000000a R09:
> 00007f7a161bf740
> [   28.337953] R10: 0000000000000008 R11: 0000000000000246 R12:
> 0000000000000000
> [   28.337953] R13: 0000000000000000 R14: 0000000000000002 R15:
> 00007ffc606ba860
> [   28.337953] FS:  00007f7a161bf740(0000) GS:ffff88001fc00000(0000)
> knlGS:0000000000000000
> [   28.337953] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [   28.337953] CR2: 00007ffc606b8ff8 CR3: 000000001f71a000 CR4:
> 00000000000006f0
> [   28.337953] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
> 0000000000000000
> [   28.337953] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7:
> 0000000000000400
> [   28.337953] Stack:
> [   28.337953]  0000000000000000 00007ffc606b90f8 ffffffff8168eb88
> 00007ffc606ba860
> [   28.337953]  0000000000000002 0000000000000000 0000000000000000
> 00007ffc606b90f8
> [   28.337953]  00007ffc606b9108 0000000000000246 0000000000000008
> 00007f7a161bf740
> [   28.337953] Call Trace:
> [   28.337953] Code: 89 de 4c 89 ef e8 7c ca fe ff e9 5c fd ff ff 31 c0
> e9 01 ff ff ff 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5
> 41 55 <41> 54 49 89 f4 53 48 89 fb 48 83 ec 08 0f 20 d0 0f 1f 40 00 0f
> [   28.337953] RIP  [<ffffffff8169294b>] do_page_fault+0xb/0x90
> [   28.337953]  RSP <00007ffc606b9000>
> [   28.337953] ---[ end trace b556ad308185dda4 ]---
> [   28.337953] Kernel panic - not syncing: Fatal exception
> 
> Can somebody give me a hint how can I debug this?

Hi Ján,

Unfortunately, I'm not very familiar with the internals of Linux. What I
might suggest trying to do is to maybe test with migrating SmartOS, only
because it'll hopefully be easier for us to look at dumps, get a crash
dump, and debug.

I suspect that likely what's going on here is that some part of the
migrated state has not been correctly saved and/or restored, especially
given that we never really focused on bring up at the time.

Sorry I don't have a more actionable next step for you.

Robert


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