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[Xen-devel] Re: [Patch] Enable "sysrq c" handler for domU coredump

To: Horms <horms@xxxxxxxxxxxx>, Muli Ben-Yehuda <muli@xxxxxxxxxx>, Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: [Xen-devel] Re: [Patch] Enable "sysrq c" handler for domU coredump
From: Akio Takebe <takebe_akio@xxxxxxxxxxxxxx>
Date: Tue, 01 Aug 2006 18:06:35 +0900
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Akio Takebe <takebe_akio@xxxxxxxxxxxxxx>, Kouya Shimura <kouya@xxxxxxxxxxxxxx>
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>On Tue, Aug 01, 2006 at 01:39:23PM +0900, Akio Takebe wrote:
>> Hi, Horms
>> >
>> >That seems fine to me. Though there was some resistance to a
>> >patch I sent which adds a panic option to xen-console, which
>> >is the hypervisor equivalent of sysrq.
>> >
>> This patch focus only manually dumping domU's core.
>> How can I use the panic option of xen-console?
>> I thought your patch to panic xen.
>> Can I dump domU's core with the option?
>Sorry, I was not clear.
>Yes, my patch is to panic (or more recently cause a crash dump) 
>in the hypervisor. It does not give any special behaviour to
>the domains.
>What I meant was, that the idea of adding a panic to domU's sysrq
>is similar to my idea of adding panic to the xen console. And I was
>asked to change this patch to make it trigger a kdump directly,
>rather than a panic.
>I think that your sysrq patch and my xen-console panic patches
>are related, and I wanted to bring that into the discussion.
Horms, what you said, that I had better call crash_kexec() 
than panic() on dom0?
If so, I agree for dom0 directly calling crash_kexec().
But because now vmlinux is used as both dom0 and domU,
we cannot use ifdef for separateing dom0 and domU.
So I call panic() on both dom0 and domU.
I also think option like a unknown_nmi_panic is useful 
and necessary for dump and debug.

Everyone, how about the below?
1. If crash_kexec() is called on dom0, dom0 do hypercall
   then xen do kexec/kdump
2. If crash_kexec() is called on domU, domU do hypercall
   then xen do panic_domain(), and domU's core is dumped.

So I don't need to modify linux code. :-)

Or How about "xm dump"?
(Probably I use panic_domain() by hypercall.
This way can probably dump HVM domain.)

I think we need to have the way manually to dump domU, or Xen.
(Because for the time when domU or Xen don't panic 
and spinloop and so on) 

Best Regards,

Akio Takebe

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