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From: | Anthony Liguori |
Subject: | Re: [Qemu-devel] Question about qemu firmware configuration (fw_cfg) device |
Date: | Mon, 19 Jul 2010 09:45:58 -0500 |
User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.10) Gecko/20100528 Lightning/1.0b1 Thunderbird/3.0.5 |
On 07/19/2010 02:33 AM, Gleb Natapov wrote:
On Mon, Jul 19, 2010 at 08:28:02AM +0100, Richard W.M. Jones wrote:On Mon, Jul 19, 2010 at 09:23:56AM +0300, Gleb Natapov wrote:That what I am warring about too. If we are adding device we have to be sure such device can actually exist on real hw too otherwise we may have problems later.I don't understand why the constraints of real h/w have anything to do with this. Can you explain?Each time we do something not architectural it cause us troubles later. So constraints of real h/w is our constrains to.
Your constraints are purely artificial.There are plenty of places that something like fw_cfg could live and still do DMA. It can directly hang off of the Southbridge. It doesn't necessary need to be connected to the ISA/LPC buses.
Buses exist to multiplex I/O devices because of limited wiring space on motherboards. There's no reason we need to constrain ourselves to minimize the number of virtual wires we emulate.
Regards, Anthony Liguori
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