Subject: Re: [PATCH v3 3/6] vbus: add a "vbus-proxy" bus model for vbus_driver objects

From: "Michael S. Tsirkin" <[email-masked]>
Date: Tue, 18 Aug 2009 13:09:45 +0300

On Tue, Aug 18, 2009 at 01:00:25PM +0300, Avi Kivity wrote:
> On 08/18/2009 12:53 PM, Michael S. Tsirkin wrote:
>> I'm not hung up on PCI, myself.  An idea that might help you get Avi
>> on-board: do setup in userspace, over PCI.  Negotiate hypercall support
>> (e.g.  with a PCI capability) and then switch to that for fastpath. Hmm?
>>    
>
> Hypercalls don't nest well.  When a nested guest issues a hypercall, you  
> have to assume it is destined to the enclosing guest, so you can't  
> assign a hypercall-capable device to a nested guest.
> 
> mmio and pio don't have this problem since the host can use the address  
> to locate the destination.

So userspace could map hypercall to address during setup and tell the
host kernel?

> -- 
> error compiling committee.c: too many arguments to function