[PATCH v3 14/25] x86: mp: Park CPUs before running the OS

[Bin Meng]

Hi Simon,

On Mon, Jul 6, 2020 at 11:37 AM Simon Glass <sjg at chromium.org> wrote:
>
> With the new MP features the CPUs are no-longer parked when the OS is run.
> Fix this by calling a special function to park them, just before the OS is
> started.
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> Reviewed-by: Wolfgang Wallner <wolfgang.wallner at br-automation.com>
> ---
>
> Changes in v3:
> - Update the comment for mp_park_aps()
>
>  arch/x86/cpu/cpu.c        |  5 +++++
>  arch/x86/cpu/mp_init.c    | 18 ++++++++++++++++++
>  arch/x86/include/asm/mp.h | 17 +++++++++++++++++
>  3 files changed, 40 insertions(+)
>
> diff --git a/arch/x86/cpu/cpu.c b/arch/x86/cpu/cpu.c
> index d0720fb7fb..baa7dae172 100644
> --- a/arch/x86/cpu/cpu.c
> +++ b/arch/x86/cpu/cpu.c
> @@ -66,6 +66,11 @@ static const char *const x86_vendor_name[] = {
>
>  int __weak x86_cleanup_before_linux(void)
>  {
> +       int ret;
> +
> +       ret = mp_park_aps();
> +       if (ret)
> +               return log_msg_ret("park", ret);
>         bootstage_stash((void *)CONFIG_BOOTSTAGE_STASH_ADDR,
>                         CONFIG_BOOTSTAGE_STASH_SIZE);
>
> diff --git a/arch/x86/cpu/mp_init.c b/arch/x86/cpu/mp_init.c
> index bcb7513084..0bf325ae88 100644
> --- a/arch/x86/cpu/mp_init.c
> +++ b/arch/x86/cpu/mp_init.c
> @@ -651,6 +651,24 @@ int mp_run_on_cpus(int cpu_select, mp_run_func func, void *arg)
>         return 0;
>  }
>
> +static void park_this_cpu(void *unused)
> +{
> +       stop_this_cpu();
> +}
> +
> +int mp_park_aps(void)
> +{
> +       unsigned long start;
> +       int ret;
> +
> +       start = get_timer(0);
> +       ret = mp_run_on_cpus(MP_SELECT_APS, park_this_cpu, NULL);
> +       if (ret)
> +               return ret;
> +
> +       return get_timer(start);

I don't think this API should return time used for parking CPU. The
get_timer() logic should be moved to its caller instead.

> +}
> +
>  int mp_init(void)
>  {
>         int num_aps, num_cpus;
> diff --git a/arch/x86/include/asm/mp.h b/arch/x86/include/asm/mp.h
> index 3f1d70663d..4acce55b8c 100644
> --- a/arch/x86/include/asm/mp.h
> +++ b/arch/x86/include/asm/mp.h
> @@ -106,6 +106,15 @@ typedef void (*mp_run_func)(void *arg);
>   * @return 0 on success, -ve on error
>   */
>  int mp_run_on_cpus(int cpu_select, mp_run_func func, void *arg);
> +
> +/**
> + * mp_park_aps() - Park the APs ready for the OS
> + *
> + * This halts all CPUs except the main one, ready for the OS to use them
> + *
> + * @return time taken to park the APs on success (in microseconds), -ve on error
> + */
> +int mp_park_aps(void);
>  #else
>  static inline int mp_run_on_cpus(int cpu_select, mp_run_func func, void *arg)
>  {
> @@ -114,6 +123,14 @@ static inline int mp_run_on_cpus(int cpu_select, mp_run_func func, void *arg)
>
>         return 0;
>  }
> +
> +static inline int mp_park_aps(void)
> +{
> +       /* No APs to park */
> +
> +       return 0;
> +}
> +
>  #endif
>
>  #endif /* _X86_MP_H_ */

Regards,
Bin