On Thu, Feb 28, 2019 at 6:59 PM Chen Yu <yu.c.c...@intel.com> wrote:
>
> On some problematic platforms, the _PPC notifier is
> only delivered to one CPU, which might cause information
> inconsistent between CPUs within the package. Thus introduce a boot up
> parameter to broadcast this _PPC notifier onto all
> online CPUs.
>
> Signed-off-by: Chen Yu <yu.c.c...@intel.com>
> ---
> drivers/acpi/processor_perflib.c | 16 ++++++++++++++--
> 1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/processor_perflib.c
> b/drivers/acpi/processor_perflib.c
> index a303fd0e108c..737dbf5aa7f7 100644
> --- a/drivers/acpi/processor_perflib.c
> +++ b/drivers/acpi/processor_perflib.c
> @@ -63,6 +63,10 @@ module_param(ignore_ppc, int, 0644);
> MODULE_PARM_DESC(ignore_ppc, "If the frequency of your machine gets wrongly"
> \
> "limited by BIOS, this should help");
>
> +static int broadcast_ppc;
> +module_param(broadcast_ppc, int, 0644);
> +MODULE_PARM_DESC(broadcast_ppc, "Broadcast the ppc to all online CPUs");
> +
> #define PPC_REGISTERED 1
> #define PPC_IN_USE 2
>
> @@ -180,8 +184,16 @@ void acpi_processor_ppc_has_changed(struct
> acpi_processor *pr, int event_flag)
> else
> acpi_processor_ppc_ost(pr->handle, 0);
> }
> - if (ret >= 0)
> - cpufreq_update_policy(pr->id);
> + if (ret >= 0) {
> + if (broadcast_ppc) {
> + int cpu;
> +
> + for_each_possible_cpu(cpu)
> + cpufreq_update_policy(cpu);
This doesn't actually help AFAICS, because it only causes
acpi_processor_ppc_notifier() to be called for all policies, but
pr->performance_platform_limit is re-computed for the target CPU only
anyway, so the limit will only be applied to that one.
What happens in the BZ is that invoking cpufreq_update_policy() for
all CPUs causes ->verify() to run on all of them which triggers
update_turbo_state() and cpuinfo.max_freq update, because
global.turbo_disabled has changed.
That is rather less than straightforward and intel_pstate really
doesn't need any _PPC change notifications to notice that the
MSR_IA32_MISC_ENABLE_TURBO_DISABLE bit has changed as it checks that
bit on every P-state update.
So no, we are not going to do this to fix the particular issue at hand.
> + } else {
> + cpufreq_update_policy(pr->id);
> + }
> + }
> }
>
> int acpi_processor_get_bios_limit(int cpu, unsigned int *limit)
> --
> 2.17.1
>
