Re: [Qemu-devel] Adding another debug protocol

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2012-11-14 15:40, Peter Cheung wrote:
> Hi   Cannot use gdb protocol, because it is slow.

For any practical purpose I came across so far while debugging guest
kernels, that is not true when running against QEMU. Sure, if you want
to dump gigabytes of RAM this way, it will be a bottleneck. But when do
you have to do this while interactively debugging? Printing the content
will still take longer than transmitting it.

> Also, the original gdb stub can dump out GDT/IDT/CR0 directly.

That is true, but it should be addressed in gdb. Folks there are aware
of the issue and will happily discuss extension proposals and likely
also take the necessary patches. It will be trivial to adapt QEMU to
such an extension afterward.

Also, this is a temporary, just too long pending issue for x86. I'm not
aware of such limitations for other architectures.

And there is actually workaround for the meantime: issue "monitor info
registers" in the gdb session to obtain also those registers. "monitor
cpu N" will allow you to switch between CPUs. It's not nice but saved my
days a few times already.

Jan

> 
> Thanksfrom Peter
> 
>> Date: Wed, 14 Nov 2012 10:54:02 +0000
>> From: peter.maydell@linaro.org
>> To: mcheung63@hotmail.com
>> CC: qemu-devel@nongnu.org
>> Subject: Re: [Qemu-devel] Adding another debug protocol
>>
>> On 14 November 2012 10:45, Peter Cheung <mcheung63@hotmail.com> wrote:
>>> Dear All
>>>     I am going to add another debugger server into QEMU, so i need to
>>> 1) create another socket server, similar than gdbserver, to receive the
>>> command from debugger
>>> 2) add another option, such as "--start-debugger-server" to start the socket
>>> server.
>>>
>>> After I work out the whole thing, how can i ask for the qemu maintainer to
>>> accept my code? I believe i should write a proposal first.
>>
>> Probably worth including a summary of why your second debug protocol
>> couldn't be implemented as a translation layer between gdbserver
>> protocol and whatever it is you need.
>>
>> -- PMM
>>
>  		 	   		  
> 

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