Re: [Xen-devel] [PATCH RFC 33/35] arm : acpi enable efi for acpi

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 11.02.15 at 10:57, <julien.grall@xxxxxxxxxx> wrote:
> Hi Ian,
> 
> On 05/02/2015 20:05, Ian Campbell wrote:
>> On Thu, 2015-02-05 at 11:58 +0000, Jan Beulich wrote:
>>>>>> On 05.02.15 at 06:31, <julien.grall@xxxxxxxxxx> wrote:
>>>>> --- a/xen/common/efi/runtime.c
>>>>> +++ b/xen/common/efi/runtime.c
>>>>> @@ -11,7 +11,13 @@ DEFINE_XEN_GUEST_HANDLE(CHAR16);
>>>>>    #ifndef COMPAT
>>>>>
>>>>>    #ifdef CONFIG_ARM  /* Disabled until runtime services implemented */
>>>>
>>>> This comment seems irrelevant now.
>>>>
>>>>> +
>>>>> +#if defined(CONFIG_ARM_64) && defined(CONFIG_ACPI)
>>>>
>>>> #ifdef CONFIG_ACPI
>>>
>>> This is common code, and I can't see ACPI and EFI being always in the
>>> same supported state (or else we could drop one of the two).
>>
>> EFI without ACPI is certainly a possibility on ARM64.
> 
> We would need to defined a new protocol in order to boot ACPI without EFI.
> 
> Currently the ACPI fetch the rsdp pointer in 2 differents way depending 
> of efi_enabled:
>       * efi_enabled == 1 => Use EFI to get the pointer
>       * efi_enabled == 0 => Use the x86 legacy mode
> 
> On ARM64, we have to use the first one.

How that when not booting from EFI? Surely you can't use x86
legacy mode, but if there is the possibility of ACPI without EFI
(the opposite of what Ian indicated would be a possibility), then
there ought to be another method to find RSDP on ARM too.

> Maybe we should refactor acpi_os_get_root_pointer?

If need be...

Jan


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