Re: [Xen-devel] Re: Test results for save/restore with upstream pv_ops domU kernels, 2.6.32.7 works OK

[Andrew Jones <drjones@xxxxxxxxxx>]

On 02/01/2010 04:10 PM, Pasi Kärkkäinen wrote:
> On Fri, Jan 29, 2010 at 12:53:38PM +0200, Pasi Kärkkäinen wrote:
>> On Fri, Jan 29, 2010 at 10:35:32AM +0000, Ian Campbell wrote:
>>> On Thu, 2010-01-28 at 21:25 +0000, Pasi Kärkkäinen wrote:
>>>> Hello,
>>>>
>>>> I just tried some save/restore tests with Fedora 12 Linux 2.6.31.12 
>>>> kernels.
>>>> The exact Fedora kernel versions are: 2.6.31.12-174.2.3.fc12.i686.PAE and 
>>>> 2.6.31.12-174.2.3.fc12.x86_64.
>>>>
>>>> Dom0 for these tests was CentOS 5.4 (Xen 3.1.2).
>>>>
>>>> - F12 32bit 1vcpu PV guest: 
>>>>    save+restore OK, BUG() in guest dmesg after restore [1]
>>>>
>>>> - F12 64bit 1vcpu PV guest:
>>>>    save+restore OK, BUG() in guest dmesg after restore [2]
>>>
>>> I think those are the same underlying bug and are fixed by 
>>> http://git.kernel.org/?p=linux/kernel/git/jeremy/xen.git;a=commit;h=777df2b017ef34b2d1a172bf769582158839a860
>>>
>>
>> Ok. 
>>
>> There was also this traceback in the beginning of boot, on all 32bit/64bit, 
>> 1vcpu2/vcpu guest combinations:
>>
>> Performance Counters: Core2 events, Intel PMU driver.
>> ------------[ cut here ]------------
>> WARNING: at arch/x86/kernel/apic/apic.c:247 
>> native_apic_write_dummy+0x32/0x3e() (Not tainted)
>> Modules linked in:
>> Pid: 0, comm: swapper Not tainted 2.6.31.12-174.2.3.fc12.i686.PAE #1
>> Call Trace:
>>  [<c043db4b>] warn_slowpath_common+0x70/0x87
>>  [<c041cfb2>] ? native_apic_write_dummy+0x32/0x3e
>>  [<c043db74>] warn_slowpath_null+0x12/0x15
>>  [<c041cfb2>] native_apic_write_dummy+0x32/0x3e
>>  [<c0411e04>] perf_counters_lapic_init+0x30/0x32
>>  [<c09b3b1b>] init_hw_perf_counters+0x2bc/0x355
>>  [<c09b3628>] identify_boot_cpu+0x21/0x23
>>  [<c09b378e>] check_bugs+0xb/0xdc
>>  [<c047fd73>] ? delayacct_init+0x47/0x4c
>>  [<c09ab8b4>] start_kernel+0x31c/0x330
>>  [<c09ab081>] i386_start_kernel+0x70/0x77
>>  [<c09ae2bb>] xen_start_kernel+0x4b9/0x4c1
>>  [<c04090a1>] ? syscall_exit+0x1/0x16
>> ---[ end trace a7919e7f17c0a725 ]---
>>
>> Full boot logs here:
>> http://pasik.reaktio.net/xen/debug/fedora/
>>
> 
> 
> This boot-time traceback disappeared when I updated the guest to 2.6.32.7.
> 
> 
>>
>>>>
>>>> - F12 32bit 2vcpu PV guest:
>>>>    save doesn't work, guest stays as "migrating-f12test32" in "xm list" 
>>>> forever and has to be "xm destroy"ed.
>>>>
>>>> - F12 64bit 2vcpu PV guest:
>>>>    save doesn't work, guest stays as "migrating-f12test64" in "xm list" 
>>>> forever and has to be "xm destroy"ed.
>>>>
>>>>
>>>> What's the best way to debug failing "xm save" ? There was no errors in 
>>>> "xm log", or in "xm dmesg".
>>>
>>> I think you might see some stuff in /var/log/xen/something but I don't
>>> have any particular tips apart from "add printf/printk".
>>>
>>
>> I'll check /var/log/xen/.
>>
>>>> Also the guest "xm console" doesn't show anything before it dies.
>>>>
>>>> Is it possible some of the save/restore related patches didn't make it to 
>>>> 2.6.31.x stable kernels? 
>>>
>>> AFAIK they only went into the 2.6.32 stable branch. Unfortunately I
>>> think the 2.6.31 stable series has come to an end now.
>>>
>>
>> Ok. I'll test 2.6.32.latest aswell.
>>
> 
> I grabbed upstream kernel.org Linux 2.6.32.7, and tested the following 
> combinations:
> 
> - F12 32bit 1vcpu PV guest
> - F12 32bit 2vcpu PV guest
> - F12 64bit 1vcpu PV guest
> - F12 64bit 2vcpu PV guest
> 
> save+restore was successfull for all of the above guests running 2.6.32.7. 
> No BUGs or tracebacks anymore.
> 
> Any tips for git magic to get all the recent save/restore fixes that went to 
> 2.6.32.x,
> so I could send them to Fedora people to apply to F12 kernel? 
> 

This is great news, but it might a good idea to try 2 or more
save-restore rounds in row first, if you haven't already. In the past
I've seen 1 save/restore work, but then the 2nd round fail. Although,
usually there's some symptom of badness on the 1st round as well.

Thanks,
Andrew


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