Re: of cows and clones: creating domains as clones of saved state

[Peri Hankey <mpah@thegreen.co.uk>]

Keir

You had in fact seen this in an earlier thread: 'crash when domain is 
restored', which was confirmed as occurring by Charles Coffing.  You 
suggested I add instrumentation. I haven't yet had a chance to do that, 
but I'll first try it with xen-unstable.

But I'll be interested to hear whether you think there is any mileage in 
my clone proposal.

Regards
Peri

your comment:

>Looks easy to fix. You might want to instrument up time_resume in
>arch/xen/i386/kernel/time.c, or I may find some time to look later in
>the week.
>
> -- Keir
>

my message:

> I hadn't yet investigated save/restore, but it seems not to work for 
> me. Running Mandrakelinux 10.1 (ish - updated not reinstalled) on an 
> AMD ATHLON 2400 I have a crash restoring the domain:
>
>    root@xen0# xm save aaa aaa.saved
>    ...
>    root@xen0# xm restore aaa.saved
>
> The console output is as follows:
>
> Unable to handle kernel paging request at virtual address 0000c000
> printing eip:
> *pde = ma 00000000 pa 55555000
> Oops: 0002 [#1]
> PREEMPT
> Modules linked in: loop
> CPU:    0
> EIP:    0061:[<c0311000>]    Not tainted VLI
> EFLAGS: 00010206   (2.6.9-xenU)
> EIP is at early_serial_init+0x1c/0x1d5
> eax: c02ca510   ebx: 0000c000   ecx: fbffc000   edx: 00000001
> esi: 00000010   edi: c0102000   ebp: 00000000   esp: c10ebf20
> ds: 0069   es: 0069   ss: 0069
> Process events/0 (pid: 3, threadinfo=c10ea000 task=c10d9020)
> Stack: c010e7c8 00000000 c0109e4d fbffc000 000001d3 00000063 c36a6000 
> c10ea000
>       00000000 c02c9580 00000000 c012cd23 00000000 c10ebf74 00000000 
> c10ad278
>       c0109f4f c10ea000 c10ad268 ffffffff ffffffff 00000001 00000000 
> c01195c6
> Call Trace:
> [<c010e7c8>] time_resume+0x12/0x52
>
> [<c0109e4d>] __do_suspend+0x1a0/0x1e1
>
> [<c012cd23>] worker_thread+0x1ea/0x2fe
>
> [<c0109f4f>] __shutdown_handler+0x0/0x48
>
> [<c01195c6>] default_wake_function+0x0/0x12
>
> [<c01195c6>] default_wake_function+0x0/0x12
>
> [<c012cb39>] worker_thread+0x0/0x2fe
>
> [<c0130f94>] kthread+0xa8/0xde
>
> [<c0130eec>] kthread+0x0/0xde
>
> [<c010f091>] kernel_thread_helper+0x5/0xb
>
> Code: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 <c0> 
> 3b 39 98 00 00 00 02 00 00 1c 7e 00 00 00 00 00 00 00 00 00



Keir Fraser wrote:

>>Xen can already save the state of an established domain and restore it 
>>(in theory at least - so far it crashes for me).
>>    
>>
>
>How does it crash for you? I can save/restore a 2.6.9-xenU domain
>built from latest 2.0-testing tree with no problems.
>
> -- Keir
>
>
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