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

8 Jan 2018


      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@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