Re: [Qemu-devel] [PATCH v3 2/3] machine: make MemoryHotplugState accessible via the machine

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Apr 23, 2018 at 11:36:48AM +0200, David Hildenbrand wrote:
> On 23.04.2018 05:28, David Gibson wrote:
> > On Fri, Apr 20, 2018 at 02:34:55PM +0200, David Hildenbrand wrote:
> >> Let's allow to query the MemoryHotplugState from the machine.
> >>
> >> This allows us to generically detect if a certain machine has support
> >> for memory devices, and to generically manage it (find free address
> >> range, plug/unplug a memory region).
> >>
> >> Signed-off-by: David Hildenbrand <david@redhat.com>
> > 
> > So, we're creating a hook where it seems very likely that the only
> > implementationss will be simply to retrieve the right field from the
> > machine specific structure.
> > 
> > So.. should we instead just move the hotplug_memory structure to the
> > based MachineState type?
> 
> It allows us in patch nr. 3 to report different error messages.
> 
> "Not supported" vs. "Not enabled (maxmem)".
> 
> We could also handle that via a simple boolean flag inside of the
> struct. What do you think?

A third option would be to make it a pointer, rather than directly
embedded in the MachineState.  That would also avoid the extra
allocation for machines that don't use it.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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