Re: [Qemu-devel] Using PCI config space to indicate config location

[Michael S. Tsirkin]

On Wed, Oct 10, 2012 at 02:14:11PM +1030, Rusty Russell wrote:
> > See above.  A guest could happily just use BAR1/BAR2 and completely
> > ignore BAR0 provided that BAR1/BAR2 are present.
> 
> But x86 guests want BAR0 because IO space is faster than MMIO.  Right?

Or to be a bit more precise, ATM on x86 emulating IO instructions is
faster than MMIO. IIUC this is since you get the address/data in
registers and don't need to decode them.

-- 
MST