[U-Boot] [U-Boot, V3, 2/3] ARM: tegra: reserve unmapped RAM so EFI doesn't use it

[Alexander Graf]

On 20.09.18 21:11, Stephen Warren wrote:
> On 09/01/2018 03:58 AM, Alexander Graf wrote:
>>> From: Stephen Warren <swarren at nvidia.com>
>>>
>>> Tegra U-Boot ensures that board_get_usable_ram_top() never returns a
>>> value
>>> over 4GB, since some peripherals can't access such addresses.
>>> However, on
>>> systems with more than 2GB of RAM, RAM bank 1 does describe this extra
>>> RAM, so that Linux (or whatever OS) can use it, subject to DMA
>>> limitations. Since board_get_usable_ram_top() points at the top of RAM
>>> bank 0, the memory locations describes by RAM bank 1 are not mapped by
>>> U-Boot's MMU configuration, and so cannot be used for anything.
>>>
>>> For some completely inexplicable reason, U-Boot's EFI support ignores
>>> the
>>> value returned by board_get_usable_ram_top(), and EFI memory allocation
>>> routines will return values above U-Boot's RAM top. This causes
>>> U-Boot to
>>> crash when it accesses that RAM, since it isn't mapped by the MMU. One
>>> use-case where this happens is TFTP download of a file on Jetson TX1
>>> (p2371-2180).
>>>
>>> This change explicitly tells the EFI code that this extra RAM should not
>>> be used, thus avoiding the crash.
>>>
>>> A previous attempt to make EFI honor board_get_usable_ram_top() was
>>> rejected. So, this patch will need to be replicated for any board that
>>> implements board_get_usable_ram_top().
>>>
>>> Fixes: aa909462d018 ("efi_loader: efi_allocate_pages is too
>>> restrictive")
>>> Signed-off-by: Stephen Warren <swarren at nvidia.com>
>>
>> Thanks, applied to efi-next
> 
> They don't seem to have shown up in u-boot/master though...

Yes, thanks to the new sandbox support we were able to run more tests
than before and suddenly caught one that only got fixed very recently.
Because of that we didn't pass travis and I didn't want to send a pull
request that would break our automated testing :)

Should be on its way soon (today if things work out as planned).


Alex