Re: [Xen-devel] Criteria for dom0_gnttab_start

[Julien Grall <julien.grall@xxxxxxxxxx>]

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.

Regards,

-- 
Julien Grall

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