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Re: [Xen-devel] of cows and clones: creating domains as clones of saved

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] of cows and clones: creating domains as clones of saved state
From: Peri Hankey <mpah@xxxxxxxxxxxxxx>
Date: Thu, 25 Nov 2004 22:13:44 +0000
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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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Read honest & candid reviews on hundreds of IT Products from real users.
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