Re: [Xen-devel] [PATCH] xen/arm: Implement domain_get_maximum_gpfn

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2014-07-02 at 12:51 +0200, Roger Pau Monnà wrote:
> On 02/07/14 12:31, Jan Beulich wrote:
> >>>> On 02.07.14 at 12:19, <roger.pau@xxxxxxxxxx> wrote:
> >> For PVH guests there's still no MMIO hole (or any other kind of hole) at
> >> all, the hole(s) is only there for Dom0.
> > 
> > So where would passed through devices get their MMIO BARs located?
> > (I realize pass-through isn't supported yet for PVH, but I didn't expect
> > such fundamental things to be missing.)
> 
> We could always add a MMIO region to a PVH guest in backwards compatible
> way, the only requirement is to make sure the e820 provided to the guest
> has this hole set up, but I see no reason to add it before having this
> functionality, or to add it unconditionally to guests even if no devices
> are passed through.
> 
> Also, shouldn't PVH guests use pcifront/pciback, which means it won't
> have any BARs mapped directly?

They need to map them somewhere in their physical address to be able to
use them... (Unlike a PV guest which I think maps them in the virtual
address space "by magic" avoiding the need for a p2m entry).

Ian.


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