Re: [Qemu-devel] [PATCH 0/2][RFC] postcopy migration: Linux char device for postcopy

[Avi Kivity]

On 01/04/2012 05:03 AM, Isaku Yamahata wrote:
> Yes, it's quite doable in user space(qemu) with a kernel-enhancement.
> And it would be easy to convert a separated daemon process into a thread
> in qemu.
>
> I think it should be done out side of qemu process for some reasons.
> (I just repeat same discussion at the KVM-forum because no one remembers
> it)
>
> - ptrace (and its variant)
>   Some people want to investigate guest ram on host (qemu stopped or lively).
>   For example, enhance crash utility and it will attach qemu process and
>   debug guest kernel.

To debug the guest kernel you don't need to stop qemu itself.   I agree
it's a problem for qemu debugging though.

>
> - core dump
>   qemu process may core-dump.
>   As postmortem analysis, people want to investigate guest RAM.
>   Again enhance crash utility and it will read the core file and analyze
>   guest kernel.
>   When creating core, the qemu process is already dead.

Yes, strong point.

> It precludes the above possibilities to handle fault in qemu process.

I agree.


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