Re: correct way to reserve memory from PrePi?

[Michael Zimmermann <sigmaepsilon92@gmail.com>]

I've enabled GCD debugging and apparently it doesn't accept the allocation:
GCD:AllocateMemorySpace(Base=0000000090000000,Length=0000000010000000)
  GcdAllocateType = AtAddress
  GcdMemoryType   = SystemMem
  Alignment       = 0000000000000001
  ImageHandle     = FDE28F90
  DeviceHandle    = 0
CoreAllocateSpaceCheckEntry:982 handle=FDE28F90
CoreAllocateSpace:1130
  Status = Not Found
GCDMemType Range                             Capabilities
Attributes
========== ================================= ================
================
NonExist   0000000000000000-000000007FFFFFFF 0000000000000000
0000000000000000
SystemMem  0000000080000000-00000000FDFFFFFF 800000000000000E
0000000000000000*
NonExist   00000000FE000000-00000000FE3FFFFF 0000000000000000
0000000000000000
SystemMem  00000000FE400000-00000000FFFE5FFF 800000000000000E
0000000000000000
SystemMem  00000000FFFE6000-00000000FFFEEFFF 800000000000000E
0000000000000000*
SystemMem  00000000FFFEF000-00000000FFFFFFFF 800000000000000E 0000000000000000


It fails in this line:
https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Core/Dxe/Gcd/Gcd.c#L982
In this example I've used(start,size) 0x80000000,0x80000000 for the
resource descriptors.
If I use 0x80000000,0x40000000 and 0xc0000000,0x40000000 everything
works just fine.

Thanks
Michael

On Wed, Dec 14, 2016 at 4:13 PM, Michael Zimmermann
<sigmaepsilon92@gmail.com> wrote:
> 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