Re: [PATCH v15 3/6] x86/boot: Introduce efi_get_rsdp_addr() to find RSDP from EFI table

Chao Fan
2019-01-15T07:22:25Z

On Mon, Jan 14, 2019 at 10:07:56AM +0100, Borislav Petkov wrote:
>On Mon, Jan 14, 2019 at 09:26:42AM +0800, Chao Fan wrote:
>> According to the code, I saw:
>> #ifdef ACPI_ASL_COMPILER
>> #define ACPI_32BIT_PHYSICAL_ADDRESS
>> #endif
>>
>> and then
>> #ifdef ACPI_32BIT_PHYSICAL_ADDRESS
>> typedef u32 acpi_physical_address;
>>
>> As for ACPI_ASL_COMPILER, I saw iASL in documention, but can't find more
>> information in the code. If I miss something, please let me know.
>
>And, as a result, can acpi_physical_address ever be u32 in a kernel
>build?

In my understanding after looking into the commit message the comments.
I thinks yes. For 32-bit OS:
32-bit OS without PAE, it's u32.
32-bit OS with PAE in 64-bit machine, it's u64.

So I thinks there is some situations where it's u32.
'acpi_physical_address' was always u32 for 32-bit OS, and then to
solve some problems, "Zheng, Lv" add the commit. So I have added to Cc
"Zheng, Lv" , I am not sure whether "Zheng, Lv" can give some suggestion
about when acpi_physical_address is defined as u32.

Thanks,
Chao Fan

>
>git annotate is also very helpful when doing git archeology like, for
>example, finding the patch which added the ifdeffery and looking at its
>commit message for more hints.
>
>--
>Regards/Gruss,
> Boris.
>
>Good mailing practices for 400: avoid top-posting and trim the reply.
>
>