Re: [PATCH RFC 26/35] arm : acpi read mmio tables from uefi

[Julien Grall <julien.grall@linaro.org>]

Hi Stefano,

On 06/02/2015 22:17, Stefano Stabellini wrote:
> On Fri, 6 Feb 2015, Julien Grall wrote:
>> On 06/02/2015 00:34, Stefano Stabellini wrote:
>>>> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
>>>> index 93c8a8a..930746b 100644
>>>> --- a/xen/arch/arm/setup.c
>>>> +++ b/xen/arch/arm/setup.c
>>>> @@ -50,6 +50,7 @@
>>>>    #include <asm-arm/cputype.h>
>>>>
>>>>    struct bootinfo __initdata bootinfo;
>>>> +struct meminfo __initdata acpi_mmio;
>>>>
>>>>    struct cpuinfo_arm __read_mostly boot_cpu_data;
>>>>
>>>> diff --git a/xen/include/asm-arm/setup.h b/xen/include/asm-arm/setup.h
>>>> index ba5a67d..5ea9ed6 100644
>>>> --- a/xen/include/asm-arm/setup.h
>>>> +++ b/xen/include/asm-arm/setup.h
>>>> @@ -46,6 +46,7 @@ struct bootinfo {
>>>>    };
>>>>
>>>>    extern struct bootinfo bootinfo;
>>>> +extern struct meminfo acpi_mmio;
>>>
>>> It might make sense to reuse bootinfo.mem.
>>
>> Do you mean by extending the meminfo structure with a flags indicating if it's
>> a RAM or MMIO range?
>
> Right.  We could avoid introducing acpi_mmio and instead storing the
> banks info in bootinfo.mem, that I am guessing it would be unused on
> acpi?

It's used by EFI to store the memory bank. So we can't reuse it for 
another purpose.

But we could extend the structure to add a type.

Although, let's wait until we know if we can use UEFI to get the MMIO 
region.

>
>> I guess it might be good, but I'm concerned about the static size of the
>> array, 64 may not be suffisant.
>
> Yes, you are right about that.  Do we have any ideas on how many banks
> are available on a few real systems?

I have no ideas.

> The alternative would be to create a list.

At that time, we can't use the boot allocator (memory has not been 
populate). We would have to use the AllocatePages().

Regards,

-- 
Julien Grall