Re: [Xen-devel] Design doc of adding ACPI support for arm64 on Xen - version 3

["Jan Beulich" <jbeulich@xxxxxxxx>]

>>> Shannon Zhao <zhaoshenglong@xxxxxxxxxx> 08/18/15 5:46 AM >>>
>On 2015/8/17 23:33, Jan Beulich wrote:
>>>>> On 14.08.15 at 16:59, <shannon.zhao@xxxxxxxxxx> wrote:
>>> 1. Copy and change some EFI and ACPI tables
>>> -------------------------------------------
>> 
>> While some explanation on the reasons for this was given in the past
>> discussion, I'm still missing a word on the "why" for each of these here.
>> 
>>> a) Copy EFI_SYSTEM_TABLE and change the value of FirmwareVendor,
>>> VendorGuid, VendorTable, ConfigurationTable. These changes are not very
>>> special and it just assign values to these members.
>> 
>> I continue to question the need for fiddling with this table, not the
>> least because I don't see how you intend to hand it to the Dom0
>> kernel: Are you expecting to call the kernel's ordinary EFI entry
>> point, despite it not itself running on EFI firmware?
>> 
>Dom0 gets UEFI info from the minimal DT when booting with UEFI.
>And the main purpose to create a EFI_SYSTEM_TABLE is to provide the ACPI
>table root (RSDP) address to Dom0, so it could find the ACPI table.

For that passing the configuration table would suffice. The more that Julien
in his reply said you're not even intending to use the kernel's EFI stub. I.e.
the question remains: How would you expect to hand the System Table
pointer to Dom0?

>Here since we don't support RUNTIME service fro Dom0 currently, we could
>set the Attribute of EFI_SYSTEM_TABLE memory region to not be
>EFI_MEMORY_RUNTIME or pass kernel command parameter "efi=noruntime" to
>disable RUNTIME service.

I don't see how this part of your reply is related.

>>> g) Change the value of xsdt_physical_address in RSDP table.
>> 
>> Which RSDP? Under EFI the table root is to be found from the
>> EFI Configuration Table.
>> 
>Yes, the RSDP address is stored in EFI Configure Table. And RSDP table
>has a field "xsdt_physical_address" that points to the XSDT table. As we
>create a new XSDT and the address of XSDT is changed, so it needs to
>update the value of "xsdt_physical_address" in RSDP. So Dom0 could get
>the right XSDT table rather than the old one.

Oh, sorry, I mixed things up.

Jan


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