Re: [Xen-devel] [PATCH v5 2/3] pc & q35: Add new machine opt max-ram-below-4g

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Tue, Jun 17, 2014 at 04:08:54PM -0400, Konrad Rzeszutek Wilk wrote:
> On Tue, Jun 17, 2014 at 10:43:29PM +0300, Michael S. Tsirkin wrote:
> > On Tue, Jun 17, 2014 at 02:44:41PM -0400, Don Slutz wrote:
> > > 
> > > >Presumably you then have a 64 bit guest so why does it
> > > >care about memory/MMIO being below 4G?
> > > 
> > > It is not the guest that matters, it is all the PCI devices in use. There 
> > > are
> > > ones (all old hardware) that only support 32bit addresses.
> > 
> > Emulated devices? Let's just teach them to support 64 bit BARs.
> > Looks like a nicer solution than asking user to make
> > this decision.
> 
> I presume real normal PCI devices.
>

Yeah, I believe this thread is about enabling/fixing PCI passthru of (existing 
old legacy) physical PCI devices,
so there's no way to "teach" them to support 64b BARs..


> > 
> > >  When using
> > > these you may need more room.
> > > 
> > > Also pci-passthru of real hardware that is 32bit only may require this.
> > >    -Don Slutz
> > 


-- Pasi


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