Re: [Qemu-devel] [Question] dump memory when host pci device is used by guest

[Jan Kiszka]

On 2011-10-10 11:02, Daniel P. Berrange wrote:
> On Mon, Oct 10, 2011 at 08:52:08AM +0200, Jan Kiszka wrote:
>> On 2011-10-10 04:21, Wen Congyang wrote:
>>> At 10/09/2011 06:23 PM, Richard W.M. Jones Write:
>>>> On Sun, Oct 09, 2011 at 10:49:57AM +0200, Jan Kiszka wrote:
>>>>> As explained in the other replies: It is way more future-proof to use an
>>>>> interface for this which was designed for it (remote gdb) instead of
>>>>> artificially relaxing reasonable constraints of the migration mechanism
>>>>> plus having to follow that format with the post-processing tool.
>>>>
>>>> Any interface that isn't "get this information off my production
>>>> server *now*" so that I can get the server restarted, and send it to
>>>> an expert to analyse -- is a poor interface, whether it was designed
>>>> like that or not.  Perhaps we don't have the right interface at all,
>>>> but remote gdb is not it.
>>>
>>> What about the following idea?
>>>
>>> Introduce a new monitor command named dump, and this command accepts a 
>>> filename.
>>> We can use almost all migration's code. We use this command to dump guest's
>>> memory, so there is no need to check whether the guest has a unmigratable 
>>> device.
>>
>> I do not want to reject this proposal categorically, but I would like to
>> see the gdb path fail /wrt essential requirements first. So far I don't
>> see it would.
> 
> GDB is often forbidden on production servers, so that path is
> clearly not an option, unless we want libvirt to implement the
> GDB remote RPC protocol itself which just sounds like a world
> of hurt.

Run gdb with "set debug remote 1" and watch the communication, it is not
that complex. But a dump command is probably simpler for those
scenarios, I agree.

Jan

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