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Date: Wed, 15 Jul 2009 10:34:51 +0300
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [Qemu-devel] [PATCH] monitor: Add port write command
Message-ID: <20090715073451.GF28046@redhat.com>
References: <4A5C3FBB.10306@siemens.com> <4A5C9EDF.3060705@codemonkey.ws>
	<200907142030.27019.paul@codesourcery.com>
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To: Paul Brook <paul@codesourcery.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>, Anthony Liguori <aliguori@us.ibm.com>, qemu-devel@nongnu.org

On Tue, Jul 14, 2009 at 08:30:25PM +0100, Paul Brook wrote:
> > What would be really cool about this change is that we could introduce a
> > new set of commands to manipulate device state.  We could save/restore
> > individual device state and that would allow us to dump device state via
> > the monitor and to manipulate individual fields of the device state.  I
> > think this could be pretty useful for debugging.
> 
> I'd be reluctant to expose the savevm state to the user.
> 
> For debugging qemu I don't see it providing any real benefit over firing up 
> GDB and poking directly at the device directly.
> 
Not all environments where you need to debug things have gdb, qemu
sources or even non striped qemu binary.

> For debugging the guest there is some argument for exposing the device state 
> (preferably via the gdb stub). However I think the savevm data tends to expose 
> too many internal implementation details, rather than the interesting guest 
> state. For most devices I'd expect the IO regions to be a better fit, 
> especially if you want to prevent qemu crashing when the user does invalid 
> writes.
> 
> Paul
> 

--
			Gleb.