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

[Juergen Gross <jgross@xxxxxxxx>]

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?


Juergen

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