Re: [Xen-devel] [PATCH v2 26/41] arm : acpi add xen environment table

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Jan,

On 20/05/15 17:22, Jan Beulich wrote:
>>>> On 17.05.15 at 22:03, <parth.dixit@xxxxxxxxxx> wrote:
>> Xen environment table is ACPI table that is used to pass grant table
>> and event channel interrupt information to dom0.
> 
> The documents linked to by the uefi.org web site don't look like these
> are final, formally acceptable definitions. I'm not sure we want to
> include potentially in flux things in the hypervisor when it is not clear
> whether by the next release these would get finalized.

What do you mean by "formally acceptable definitions"?

The XENV table is final and accepted as a separate table handle by Xen
Project.

I would have to dig into my mail to find why we decide to only give a URL...

> Apart from that I could do with an explanation of why the XENV table
> is needed in the first place, considering that on x86 we get away
> without.

When you boot DOM0 on ARM there is no way to know that we are running on
Xen (no cpuid like, no specific boot path,...). For the device tree, we
include a new node. For ACPI, this table allow us to know the we are
running on Xen.

Furthermore, on x86 all these informations are passed via the start_info
structure which doesn't exits on ARM. And there would be no easy way to
pass it to DOM0 at startup (the memory layout is different from every
board).

Regards,

-- 
Julien Grall

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