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In-Reply-To: <4A5C9EDF.3060705@codemonkey.ws>
References: <4A5C3FBB.10306@siemens.com> <4A5C9EDF.3060705@codemonkey.ws>
Date: Tue, 14 Jul 2009 21:57:16 +0300
Message-ID: <f43fc5580907141157w1c2fe59fxcc6d1c11c7df96c2@mail.gmail.com>
Subject: Re: [Qemu-devel] [PATCH] monitor: Add port write command
From: Blue Swirl <blauwirbel@gmail.com>
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Jan Kiszka <jan.kiszka@siemens.com>, Anthony Liguori <aliguori@us.ibm.com>, qemu-devel <qemu-devel@nongnu.org>

On 7/14/09, Anthony Liguori <anthony@codemonkey.ws> wrote:
> Jan Kiszka wrote:
>
> > Useful for testing hardware emulations or manipulating its state to
> > stress guest drivers.
> >
> > Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> >
> >
>
>  Patch looks good.
>
>  Makes me think of an idea I had a while ago.  It's a rather radical change
> but I think we could target it for 0.12.  Today, the vast majority of our
> save/restore code looks like:
>
>  save:
>  // version checks
>  qemu_put_type(f, &field);
>  ...
>
>  load:
>  // version checks
>  qemu_get_type(f, &field);
>  ...
>  // optional depending on version
>  qemu_get_type(f, &field);
>
>  device_reset(s);
>
>  We could convert this to something this to be largely data drive.  For
> instance,
>
>  SaveVMFields fields[] = {
>  { offsetof(DeviceState, field), "field", TYPE, VERSION },
>  {},
>  };
>
>  SaveVMDescription desc = {
>   .fields = fields,
>   .version = CURRENT_VERSION,
>   .reset = device_reset,
>  };
>
>  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'm curious if anyone else is interested in this sort of change.

Excellent idea!