Re: [Xen-devel] [PATCH for-4.10] libxc: load acpi RSDP table at correct address

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.11.17 at 15:14, <jgross@xxxxxxxx> wrote:
> On 20/11/17 14:56, Boris Ostrovsky wrote:
>> On 11/20/2017 06:50 AM, Jan Beulich wrote:
>>>>>> On 20.11.17 at 12:20, <jgross@xxxxxxxx> wrote:
>>>> Which restriction? I'm loading the RSDP table to its architectural
>>>> correct addres if possible, otherwise it will be loaded to the same
>>>> address as without my patch. So I'm not adding a restriction, but
>>>> removing one.
>>> What is "architecturally correct" in PVH can't be read out of
>>> specs other than what we write down. When there's no BIOS,
>>> placing anything right below the 1Mb boundary is at least
>>> bogus.
>> 
>> Unless it's a UEFI boot -- where else would you put it? Aren't these two
>> (UEFI and non-UEFI) the only two options that the ACPI spec provides?
> 
> I think Jan is right: for PVH its _our_ job to define the correct
> placement. Which still can be the same as in the BIOS case, making
> it easier to adapt any guest systems.
> 
> So I'd say: The RSDP address in PVH case is passed in the PVH start
> info block to the guest. In case there is no conflict with the
> physical load address of the guest kernel the preferred address of
> the RSDP is right below the 1MB boundary.
> 
> Would this wording be okay?

To be honest (and in case it wasn't sufficiently clear form my
earlier replies) - I'm pretty much opposed to this below-1Mb thing.
There ought to be just plain RAM there for PVH.

Jan


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