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
