[PATCH 2/8] x86: start64: Add a hook at 64-bit entry

[Simon Glass]

Hi Aiden,

On Tue, 21 Apr 2020 at 18:45, <aiden.park at intel.com> wrote:
>
> From: Aiden Park <aiden.park at intel.com>
>
> This will allow a board or cpu to do its specific initialization
> at 64-bit entry if U-Boot is a pure 64-bit binary.
>
> Signed-off-by: Aiden Park <aiden.park at intel.com>
> ---
>  arch/x86/cpu/start64.S | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/arch/x86/cpu/start64.S b/arch/x86/cpu/start64.S
> index 7be834788b..b8ac5aab57 100644
> --- a/arch/x86/cpu/start64.S
> +++ b/arch/x86/cpu/start64.S
> @@ -13,6 +13,11 @@
>  .globl _start
>  .type _start, @function
>  _start:
> +#if defined(CONFIG_X86_RUN_64BIT_ONLY)
> +       jmp     init_64bit_entry
> +.globl init_64bit_entry_ret
> +init_64bit_entry_ret:
> +#endif

Would it be safe to do this always? Is that a standard register to
have the HOB pointer be in? If so, we could always store it. We could
also make sure that U-Boot passes it on too.

Note that U-Boot has a struct arch_spl_handoff which is how it passes
the HOB through.

>         /* Set up memory using the existing stack */
>         mov     %rsp, %rdi
>         call    board_init_f_alloc_reserve
> --
> 2.20.1
>

Regards,
Simon