[PATCH v6 10/25] x86: mp: Support APs waiting for instructions

[Bin Meng]

On Fri, Jul 17, 2020 at 10:49 PM Simon Glass <sjg at chromium.org> wrote:
>
> At present the APs (non-boot CPUs) are inited once and then parked ready
> for the OS to use them. However in some cases we want to send new requests
> through, such as to change MTRRs and keep them consistent across CPUs.
>
> Change the last state of the flight plan to go into a wait loop, accepting
> instructions from the main CPU.
>
> Drop cpu_map since it is not used.
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> Reviewed-by: Wolfgang Wallner <wolfgang.wallner at br-automation.com>
> ---
>
> (no changes since v4)
>
> Changes in v4:
> - Add a Kconfig to control this feature, enabled only on APL
>
> Changes in v3:
> - s/slow/slot/
> - Use C code instead of assembler to read/write callback pointers
> - Update commit message to mention dropping of cpu_map
>
> Changes in v2:
> - Add more comments
>
>  arch/x86/Kconfig                |   7 ++
>  arch/x86/cpu/apollolake/Kconfig |   1 +
>  arch/x86/cpu/mp_init.c          | 123 +++++++++++++++++++++++++++++---
>  arch/x86/include/asm/mp.h       |  11 +++
>  4 files changed, 134 insertions(+), 8 deletions(-)
>

Reviewed-by: Bin Meng <bmeng.cn at gmail.com>