[U-Boot] [PATCH v2 2/3] x86: fsp: Load GDT before calling FspInitEntry

[Andrew Bradford]

On 06/04 18:28, Bin Meng wrote:
> Currently the FSP execution environment GDT is setup by U-Boot in
> arch/x86/cpu/start16.S, which works pretty well. But if we try to
> move the FspInitEntry call a little bit later to better fit into
> U-Boot's initialization sequence, FSP will fail to bring up the AP
> due to #GP fault as AP's GDT is duplicated from BSP whose GDT is
> now moved into CAR, and unfortunately FSP calls AP initialization
> after it disables the CAR. So basically the BSP's GDT still refers
> to the one in the CAR, whose content is no longer available, so
> when AP starts up and loads its segment register, it blows up.
> 
> To resolve this, we load GDT before calling into FspInitEntry.
> The GDT is the same one used in arch/x86/cpu/start16.S, which is
> in the ROM and exists forever.
> 
> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
> 
> ---
> 
> Changes in v2:
> - Use CONFIG_RESET_SEG_START to avoid duplication
> 
>  arch/x86/cpu/cpu.c                | 20 ++++++++++++++++++++
>  arch/x86/cpu/start16.S            |  1 +
>  arch/x86/include/asm/u-boot-x86.h |  3 +++
>  arch/x86/lib/fsp/fsp_support.c    |  3 +++
>  4 files changed, 27 insertions(+)

Tested-by: Andrew Bradford <andrew.bradford at kodakalaris.com>