[U-Boot] [BUG] x86: incorrect dram definition in dram_init_banksize().

[Heinrich Schuchardt]

On 01/06/2018 11:51 PM, Heinrich Schuchardt wrote:
> Function efi_add_known_memory uses the configured DRAM banks
> (gd->bd->bi_dram) to define the memory that an EFI application may use.
> 
> For qemu-x86_defconfig this will result in the first 1 MB of physical
> memory being available. Here we find the BIOS, interrupt vectors and the
> VGA memory (0xA0000-0xBFFFF).
> 
> As a result grubia32.efi writes unknowingly to the video memory.
> 
> For reference:
> In function install_e820_map() we block
> [ISA_START_ADDRESS, ISA_END_ADDRESS[.
> 
> The problem seems to stem from file arch/x86/cpu/qemu/dram.c, function
> dram_init_banksize():
> 
> gd->bd->bi_dram[0].start = 0;
> gd->bd->bi_dram[0].size = gd->ram_size;
> 
> Probably exluding [ISA_START_ADDRESS, ISA_END_ADDRESS[ is not sufficient
> as this does not protect interrupt vectors.
> 
> Could you, please, provide reasonable values.
> 
> Maybe a better idea would be to define reserved memory like the ones
> that we find in the device trees, e.g.
> 
>         reserved-memory {
>                 #address-cells = <2>;
>                 #size-cells = <2>;
>                 ranges;
> 
>                 /* 16 MiB reserved for Hardware ROM Firmware */
>                 hwrom_reserved: hwrom at 0 {
>                         reg = <0x0 0x0 0x0 0x1000000>;
>                         no-map;
>                 };
> 
> But U-Boot does not yet support the concept of reserved memory.

This is how memory is reserved in arch/arm/mach-meson/board.c:

static void meson_board_add_reserved_memory(void *fdt, u64 start, u64 size)
{
       int ret;

       ret = fdt_add_mem_rsv(fdt, start, size);
       if (ret)
               printf("Could not reserve zone @ 0x%llx\n", start);

       if (IS_ENABLED(CONFIG_EFI_LOADER)) {
               efi_add_memory_map(start,
                      ALIGN(size, EFI_PAGE_SIZE) >> EFI_PAGE_SHIFT,
                      EFI_RESERVED_MEMORY_TYPE, false);
       }
}

Similar code can be found in:
arch/arm/cpu/armv8/fsl-layerscape/fdt.c
board/raspberrypi/rpi/rpi.c

Maybe we can generalize this.

> 
> Best regards
> 
> Heinrich
>