[Ksummit-2012-discuss] PCI breakout session

Benjamin Herrenschmidt benh at kernel.crashing.org
Mon Jun 18 21:04:27 UTC 2012

On Mon, 2012-06-18 at 13:52 -0700, H. Peter Anvin wrote:
> On 06/18/2012 01:48 PM, Benjamin Herrenschmidt wrote:
> > 
> > There is no excuse for sticking with IO space, really. However, again,
> > this mailing list isn't the right forum to discuss this :-)
> > 
> I disagree with that -- there is no reason to restrict non-x86 platforms
> to use IO space, but saying you can't use it for x86 guests on x86 hosts
> is preposterous.

I'n not saying you "can't use it". I'm saying using it (especially as
the sole access method) for something that is essentially emulated PCI
in this day an age is stupid.

IO space is a piece of history and should remain as such, designing new
stuff around IO space is silly. It's limitations such as the 64K overall
window accross all domains on x86 are a killer for example and trying to
increase the granularity is yet another hackish workaround akin to
plastering a wooden leg.


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