Re: [ACPI] Fw: [PATCH]: Correctly locate RSDP in EBDA

[Alan C. <al...@lx...>]

On Llu, 2005-07-25 at 15:13 -0700, Andrew Morton wrote:
>          * Scan memory looking for the RSDP signature. First search EBDA (low
>          * memory) paragraphs and then search upper memory (E0000-FFFFF).
>          */
> -       rsdp_phys = acpi_scan_rsdp (0, 0x400);
> +       rsdp_phys = acpi_scan_rsdp (*(u16*) 0x40E << 4, 0x400);

Close but no cookie. You need to read 0x40E from physical memory not
kernel virtual address space. It may also be zero which indicates that
there isn't an EBDA, sometimes interpreted as an EBDA in the top 1K or
so.