[U-Boot] [PATCH V2 1/2] ARM: tegra: reserve unmapped RAM so EFI doesn't use it

[Alexander Graf]

On 29.08.18 23:52, Heinrich Schuchardt wrote:
> On 08/29/2018 11:34 PM, Stephen Warren 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>
>> ---
>> v2:
>> - Don't hard-code EFI page size.
>> - Register RAM as a boot services data rather than reserved.
>> ---
>>  arch/arm/mach-tegra/board2.c | 14 ++++++++++++++
>>  1 file changed, 14 insertions(+)
>>
>> diff --git a/arch/arm/mach-tegra/board2.c b/arch/arm/mach-tegra/board2.c
>> index 421a71b3014d..f893966140a1 100644
>> --- a/arch/arm/mach-tegra/board2.c
>> +++ b/arch/arm/mach-tegra/board2.c
>> @@ -6,6 +6,7 @@
>>  
>>  #include <common.h>
>>  #include <dm.h>
>> +#include <efi_loader.h>
>>  #include <errno.h>
>>  #include <ns16550.h>
>>  #include <usb.h>
>> @@ -210,6 +211,19 @@ int board_early_init_f(void)
>>  
>>  int board_late_init(void)
>>  {
>> +#ifdef CONFIG_EFI_LOADER
>> +	if (gd->bd->bi_dram[1].start) {
>> +		/*
>> +		 * Only bank 0 is below board_get_usable_ram_top(), so all of
>> +		 * bank 1 is not mapped by the U-Boot MMU configuration, and so
>> +		 * we must prevent EFI from using it.
>> +		 */
>> +		efi_add_memory_map(gd->bd->bi_dram[1].start,
>> +				   gd->bd->bi_dram[1].size / EFI_PAGE_SIZE,
> 
> Are you sure all boards do the division without library function?
> This is why I prefer >> EFI_PAGE_SHIFT.
> 
> Compiling SPL fails for harmony_defconfig.
> 
>   LD      spl/common/spl/built-in.o
> arch/arm/mach-tegra/board2.c: In function ‘board_late_init’:
> arch/arm/mach-tegra/board2.c:221:3: warning: implicit declaration of
> function ‘efi_add_memory_map’; did you mean ‘fdt_add_mem_rsv’?
> [-Wimplicit-function-declaration]
>    efi_add_memory_map(gd->bd->bi_dram[1].start,
>    ^~~~~~~~~~~~~~~~~~
>    fdt_add_mem_rsv

I think that means you want #if CONFIG_IS_ENABLED(EFI_LOADER) because
the file is also compiled for SPL.


Alex