Re: Design doc of adding ACPI support for arm64 on Xen - version 2

[David Vrabel <david.vrabel@citrix.com>]

On 11/08/15 15:12, Ian Campbell wrote:
> On Fri, 2015-08-07 at 10:11 +0800, Shannon Zhao wrote:
>>
> [...]
>> 3. Dom0 gets grant table and event channel irq information
>> -----------------------------------------------------------
>> As said above, we assign the hypervisor_id be "XenVMM" to tell Dom0 that
>> it runs on Xen hypervisor.
>>
>> For grant table, add two new HVM_PARAMs: HVM_PARAM_GNTTAB_START_ADDRESS
>> and HVM_PARAM_GNTTAB_SIZE.
> 
> The reason we expose this range is essentially to allow OS authors to take
> a short cut by telling them about an IPA range which is unused, so it is
> available for remapping the grant table into. On x86 there is a BAR on the
> Xen platform PCI device which serves a similar purpose.
> 
> IIRC somebody (perhaps David V, CCd) had proposed at some point to make it
> so that Linux was able to pick such an IPA itself by examining the memory
> map or by some other scheme.

PVH in Linux uses ballooned pages which are vmap()'d into a virtually
contiguous region.

See xlated_setup_gnttab_pages().

David