Re: [PATCH 7/7] thermal: intel: hfi: Notify user space for HFI events

[Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>]

On Wed, 2021-11-24 at 16:18 +0100, Rafael J. Wysocki wrote:
> On Sat, Nov 6, 2021 at 2:34 AM Ricardo Neri
> <ricardo.neri-calderon@linux.intel.com> wrote:
> > 
> > From: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> > 
> > When the hardware issues an HFI event, relay a notification to user
> > space.
> > This allows user space to respond by reading performance and
> > efficiency of
> > each CPU and take appropriate action.
> > 
> > For example, when performance and efficiency of a CPU is 0, user
> > space can
> > either offline the CPU or inject idle. Also, if user space notices
> > a
> > downward trend in performance, it may proactively adjust power
> > limits to
> > avoid future situations in which performance drops to 0.
> > 
> > To avoid excessive notifications, the rate is limited by one HZ per
> > event.
> > To limit netlink message size, parameters for only 16 CPUs at max
> > are sent
> > in one message. If there are more than 16 CPUs, issue as many
> > messages as
> > needed to notify the status of all CPUs.
> > 
> > Cc: Andi Kleen <ak@linux.intel.com>
> > Cc: Aubrey Li <aubrey.li@linux.intel.com>
> > Cc: Tim Chen <tim.c.chen@linux.intel.com>
> > Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
> > Reviewed-by: Len Brown <len.brown@intel.com>
> > Signed-off-by: Srinivas Pandruvada < 
> > srinivas.pandruvada@linux.intel.com>
> > ---
> >  drivers/thermal/intel/Kconfig     |  1 +
> >  drivers/thermal/intel/intel_hfi.c | 55
> > ++++++++++++++++++++++++++++++-
> >  2 files changed, 55 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/thermal/intel/Kconfig
> > b/drivers/thermal/intel/Kconfig
> > index d4c6bdcacddb..b6a1f777b8e7 100644
> > --- a/drivers/thermal/intel/Kconfig
> > +++ b/drivers/thermal/intel/Kconfig
> > @@ -104,6 +104,7 @@ config INTEL_HFI
> >         bool "Intel Hardware Feedback Interface"
> >         depends on CPU_SUP_INTEL
> >         depends on SCHED_MC && X86_THERMAL_VECTOR
> > +       select THERMAL_NETLINK
> >         help
> >           Select this option to enable the Hardware Feedback
> > Interface. If
> >           selected, hardware provides guidance to the operating
> > system on
> > diff --git a/drivers/thermal/intel/intel_hfi.c
> > b/drivers/thermal/intel/intel_hfi.c
> > index 1df24b39f2e6..c669a037704e 100644
> > --- a/drivers/thermal/intel/intel_hfi.c
> > +++ b/drivers/thermal/intel/intel_hfi.c
> > @@ -24,6 +24,7 @@
> >  #include <linux/io.h>
> >  #include <linux/slab.h>
> > 
> > +#include "../thermal_core.h"
> >  #include "intel_hfi.h"
> > 
> >  #define THERM_STATUS_CLEAR_PKG_MASK (BIT(1) | BIT(3) | BIT(5) |
> > BIT(7) | \
> > @@ -124,6 +125,58 @@ static struct hfi_features hfi_features;
> >  static DEFINE_MUTEX(hfi_lock);
> > 
> >  #define HFI_UPDATE_INTERVAL    HZ
> > +#define HFI_MAX_THERM_NOTIFY_COUNT     16
> > +
> > +static int get_one_hfi_cap(struct hfi_instance *hfi_instance, int
> > cpu,
> > +                          struct hfi_cpu_data *hfi_caps)
> > +{
> > +       struct hfi_cpu_data *caps;
> > +       unsigned long flags;
> > +       s16 index;
> > +
> > +       index = per_cpu(hfi_cpu_info, cpu).index;
> > +       if (index < 0)
> > +               return -EINVAL;
> 
> When does this happen?
Highly unlikely. This can happen if somehow CPUID_HFI_LEAF is
programmed negative for a CPU, which shouldn't happen.

> 
> Can the index become negative after this check?
No. This is programmed only one time during online CPU and never
changed after that. If this is in hfi_instance->cpus, then the leaf is
already read.

> 
> Could this check be done in the caller (so this function could be a
> void one)?
Can be done.

Thanks,
Srinivas

> 
> > +
> > +       /* Find the capabilities of @cpu */
> > +       raw_spin_lock_irqsave(&hfi_instance->event_lock, flags);
> > +       caps = hfi_instance->data + index *
> > hfi_features.cpu_stride;
> > +       memcpy(hfi_caps, caps, sizeof(*hfi_caps));
> > +       raw_spin_unlock_irqrestore(&hfi_instance->event_lock,
> > flags);
> > +
> > +       return 0;
> > +}
> > +
> > +/*
> > + * Call update_capabilities() when there are changes in the HFI
> > table.
> > + */
> > +static void update_capabilities(struct hfi_instance *hfi_instance)
> > +{
> > +       struct cpu_capability cpu_caps[HFI_MAX_THERM_NOTIFY_COUNT];
> > +       int i = 0, cpu;
> > +
> > +       for_each_cpu(cpu, hfi_instance->cpus) {
> > +               struct hfi_cpu_data caps;
> > +               int ret;
> > +
> > +               ret = get_one_hfi_cap(hfi_instance, cpu, &caps);
> > +               if (ret)
> > +                       continue;
> > +
> > +               cpu_caps[i].cpu = cpu;
> > +               cpu_caps[i].perf = caps.perf_cap;
> > +               cpu_caps[i].eff = caps.ee_cap;
> > +               ++i;
> > +               if (i >= HFI_MAX_THERM_NOTIFY_COUNT) {
> > +                      
> > thermal_genl_cpu_capability_event(HFI_MAX_THERM_NOTIFY_COUNT,
> > +                                                        
> > cpu_caps);
> > +                       i = 0;
> > +               }
> > +       }
> > +
> > +       if (i)
> > +               thermal_genl_cpu_capability_event(i, cpu_caps);
> > +}
> > 
> >  static void hfi_update_work_fn(struct work_struct *work)
> >  {
> > @@ -134,7 +187,7 @@ static void hfi_update_work_fn(struct
> > work_struct *work)
> >         if (!hfi_instance)
> >                 return;
> > 
> > -       /* TODO: Consume update here. */
> > +       update_capabilities(hfi_instance);
> >  }
> > 
> >  void intel_hfi_process_event(__u64 pkg_therm_status_msr_val)
> > --
> > 2.17.1
> >