Re: [Xen-devel] Criteria for dom0_gnttab_start

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-10-21 at 13:12 +0100, Julien Grall wrote:
> On 10/21/2014 01:04 PM, Ian Campbell wrote:
> > On Tue, 2014-10-21 at 17:24 +0530, Vijay Kilari wrote:
> >>    What is the criteria for setting dom0_gnttab_start and size for a
> >> platform.
> > 
> > It simply needs to be an area of the IPA address space which is not
> > populated by anything else. Since dom0's MMIO space is mapped 1:1 with
> > the host PA address space it seems easiest/safest to find a hole in the
> > real physical space and use that.
> > 
> > If there is no such hole available then using the space occupied by some
> > device which is not passed to dom0 (e.g. is blacklisted, or used by Xen)
> > will suffice.
> > 
> > For an arm32 platform it should be below 4G.
> 
> Even on aarch64 platform, it will be better to have this range below 4G.
> 
> I'm thinking about having a 32 bit DOM0 on top on a 64 bit Xen. Though,
> this may not happen often but we are currently supported this
> possibility for DOM0.

True.

Ian.


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