Re: [Xen-devel] PCI Pass-through in Xen ARM - Draft 2.

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Mon, 2015-06-29 at 11:31 +0100, Julien Grall wrote:
> Hi Manish,
> 
> On 28/06/15 19:38, Manish Jaggi wrote:
> > 4.1 Holes in guest memory space
> > ----------------------------
> > Holes are added in the guest memory space for mapping pci device's BAR
> > regions.
> > These are defined in arch-arm.h
> > 
> > /* For 32bit */
> > GUEST_MMIO_HOLE0_BASE, GUEST_MMIO_HOLE0_SIZE
> >  
> > /* For 64bit */
> > GUEST_MMIO_HOLE1_BASE , GUEST_MMIO_HOLE1_SIZE
> 
> The memory layout for 32bit and 64bit are exactly the same. Why do you
> need to differ here?

I took this to be a "hole under 4GB" and a "hole over 4GB" IOW rather
than specific to 32-bit/64-bit guests it is specific to 32/64 bit
devices, the latter of which could be placed higher in RAM, which is
useful since the space under 4GB is naturally more limited.

Ian.


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