Message-ID: <4730B753.2000901@us.ibm.com>
Date: Tue, 06 Nov 2007 12:49:55 -0600
From: Anthony Liguori <aliguori@us.ibm.com>
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To: Rusty Russell <rusty@rustcorp.com.au>
CC: Avi Kivity <avi@qumranet.com>, Dor Laor <dor.laor@qumranet.com>,
       virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: Use of virtio device IDs
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Anthony Liguori wrote:
> Hi Rusty,
>
> I've written a PCI virtio transport and noticed something strange.  
> All current in-tree virtio devices register ID tables that match a 
> specific device ID, but any vendor ID.
>
> This is incompatible with using PCI vendor/device IDs for virtio 
> vendor/device IDs since vendors control what device IDs mean.  A 
> simple solution would be to assign a fixed vendor ID to all current 
> virtio devices.  This doesn't solve the problem completely though 
> since you would create a conflict between the PCI vendor ID space and 
> the virtio vendor ID space.
>
> The only solutions seem to be virtualizing the virtio vendor/device 
> IDs (which is what I'm currently doing) or to mandate that the virtio 
> vendor ID be within the PCI vendor ID space.  It's probably not 
> necessary to make the same requirement for device IDs though.

There's another ugly bit in the current implementation.

Right now, we would have to have every PCI vendor/device ID pair in the 
virtio PCI driver ID table for every virtio device.

This means every time a virtio device is added to Linux, the virtio PCI 
driver has to be modified (assuming that each virtio device uses a 
unique PCI vendor/device ID) :-/

Regards,

Anthony Liguori

> What are your thoughts?
>
> Regards,
>
> Anthony Liguori
>

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