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Date: Wed, 06 Jan 2010 13:50:21 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [PATCHv3] add "info ioapic" monitor command
References: <20100106163502.GQ4905@redhat.com>
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To: Gleb Natapov <gleb@redhat.com>
Cc: qemu-devel@nongnu.org, lcapitulino@redhat.com

On 01/06/2010 10:35 AM, Gleb Natapov wrote:
> Knowing ioapic configuration is very useful for the poor soles
> how need to debug guest occasionally.
>    

This needs to be implemented in terms of VMState.  There is no reason 
for it not to be.

I've just gone through the code in great detail.  You just need to 
implement a vmstate_get_field that looks up a field given an instance 
name and instance id.  You then need to add a to_str callback in 
VMStateInfo.  The vmstate_get_field code will look very much like the 
vmstate_save code except it calls to_str().

The new monitor command should be 'device_info name [instance_id] [field]'.

For the ioapic, you can introduce a new VMStateInfo type that duplicates 
the vmstate_info_uint64 type except it has a different to_str callback 
that decodes the apic fields.  It's just then a matter of a few macros 
and updating the VMState description for the ioapic.

It's the same or less code than your current patch and it lays the 
ground work for a consistent command to look up arbitrary device info.

Regards,

Anthony Liguori