Re: correct way to reserve memory from PrePi?

[Michael Zimmermann <sigmaepsilon92@gmail.com>]

As far as I know the proper way is to create resource descriptors
using BuildResourceDescriptorHob and then allocate reserved areas
using BuildMemoryAllocationHob. This way I don't have any overlapping
descriptors - I just allocated some memory very early.

I ran many tests and it looks like all calls to
BuildMemoryAllocationHob get ignored if my dram hobs look like this:
0x00000000 - 0x40000000

If I split this range into two Hob's like this everything seems to
work just fine:
0x00000000 - 0x20000000
0x20000000 - 0x20000000

I took a look at other platforms like Juno and they add big dram Hob's
(2GB and 6GB) too so why is this a problem?

Thanks
Michael

On Wed, Dec 14, 2016 at 11:21 AM, Ard Biesheuvel
<ard.biesheuvel@linaro.org> wrote:
> On 14 December 2016 at 10:02, Michael Zimmermann
> <sigmaepsilon92@gmail.com> wrote:
>> I tried both BuildResourceDescriptorHob and BuildMemoryAllocationHob
>> but apparently they don't have any effect.
>> When I look at the output of the shell's memmap command there aren't
>> any reserved/unavailable pages.
>>
>> Furthermore, when using AllocatePages with one of the physical
>> addresses which I've reserved it succeeds which means that it's not
>> just a problem of how the memmap command works.
>>
>> Am I doing something wrong or is this a bug?
>>
>
> I think you need to ensure that they don't overlap existing resource
> descriptors: if you declare a region as reserved, you should not
> declare it as memory first