[Ksummit-2012-discuss] PCI breakout session

Benjamin Herrenschmidt benh at kernel.crashing.org
Mon Jun 18 20:55:10 UTC 2012


On Mon, 2012-06-18 at 10:02 -0700, H. Peter Anvin wrote:
> On 06/18/2012 03:28 AM, Michael S. Tsirkin wrote:
> >>
> >> I'd say don't do it :-) Or rather try to give each device in the VM its
> >> own dedicated virtual host bridge & bus :-)
> > 
> > This only makes the problem of resource allocation worse.
> > For example for IO this means you waste 4K of space per device. Since
> > x86 only uses 16 bit IO addresses, this allows up to 16 devices.
> > 
> 
> OK, maybe this is a crazy idea, but we could do an extension to the PCI
> standard to allow I/O address space to be subdivided finer than 4K.  We
> could even try to push it at the PCI-SIG; it might be useful for some
> PCI-Express configurations, since PCI-Express has exactly the same issue.

Or just stop using IO space for virtio... really :-)

Cheers,
Ben.





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