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Subject: Re: [Qemu-devel] Re: [PATCH 15/15] Implement the bus structure for
	PAPR virtual IO
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Date: Sun, 13 Feb 2011 12:21:16 -0600
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Alexander Graf <agraf@suse.de>, "qemu-devel@nongnu.org List" <qemu-devel@nongnu.org>, Blue Swirl <blauwirbel@gmail.com>, Mackerras <paulus@samba.org>, anton@samba.org, Paul@gnu.org, David Gibson <david@gibson.dropbear.id.au>

On Sun, 2011-02-13 at 10:52 -0600, Anthony Liguori wrote:
> 
> A virtual bus is just an interface.  If all virtual devices that 
> interact via hcalls would all reside on the same virtual bus, then 
> having hypercalls registered through that interface makes sense
> because 
> you can associate hypercalls with particular devices.  This means
> that 
> you can automatically deregister on device removal and things like
> that.

I see. Well, VIO related h-calls are only part of the picture here, I
think we can live with having explicit de-registration if needed ;-)
Besides the h-call is still implemented even if no device -instance- is
currently plugged into the partition anyways. It just returns a (well
defined per-hcall) error code if the instance handle passed to it is
bogus.

> But I don't think this will work out well.  I think treating the 
> hypercalls as a simple dispatch table just like ioport would make
> sense.

Yup.

Cheers,
Ben.