The Intel Hardware Feedback Interface (HFI) [1] provides information about the performance and energy efficiency of each CPU in the system. It uses a table that is shared between hardware and the operating system. The contents of the table may be updated as a result of changes in the operating conditions of the system (e.g., reaching a thermal limit) or the action of external factors (e.g., changes in the thermal design power). The information that HFI provides are specified as numeric, unit-less capabilities relative to other CPUs in the system. These capabilities have a range of [0-255] where higher numbers represent higher capabilities. Energy efficiency and performance are reported in separate capabilities. If either the performance or energy capabilities efficiency of a CPU are 0, the hardware recommends to not schedule any tasks on such CPU for performance, energy efficiency or thermal reasons, respectively. The kernel or user space may use the information from the HFI to modify task placement and/or adjust power limits. This patchset focuses on the user space. The thermal notification framework is extended to relay updates of CPU capacity. Thus, a userspace daemon can affinitize workloads to certain CPUs and/or offline CPUs whose capabilities are zero. The frequency of HFI updates is specific to each processor model. On some systems, there is just a single HFI update at boot. On other systems, there may be updates every tens of milliseconds. In order to not overwhelm userspace with too many updates, they are limited to one update every CONFIG_HZ jiffies. Thanks and BR, Ricardo [1]. https://www.intel.com/sdm Ricardo Neri (5): x86/Documentation: Describe the Intel Hardware Feedback Interface x86: Add definitions for the Intel Hardware Feedback Interface thermal: intel: hfi: Minimally initialize the Hardware Feedback Interface thermal: intel: hfi: Handle CPU hotplug events thermal: intel: hfi: Enable notification interrupt Srinivas Pandruvada (2): thermal: netlink: Add a new event to notify CPU capabilities change thermal: intel: hfi: Notify user space for HFI events Documentation/x86/index.rst | 1 + Documentation/x86/intel-hfi.rst | 68 ++++ arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/include/asm/msr-index.h | 6 + drivers/thermal/intel/Kconfig | 13 + drivers/thermal/intel/Makefile | 1 + drivers/thermal/intel/intel_hfi.c | 508 ++++++++++++++++++++++++++++ drivers/thermal/intel/intel_hfi.h | 40 +++ drivers/thermal/intel/therm_throt.c | 21 ++ drivers/thermal/thermal_netlink.c | 52 +++ drivers/thermal/thermal_netlink.h | 13 + include/uapi/linux/thermal.h | 6 +- 12 files changed, 729 insertions(+), 1 deletion(-) create mode 100644 Documentation/x86/intel-hfi.rst create mode 100644 drivers/thermal/intel/intel_hfi.c create mode 100644 drivers/thermal/intel/intel_hfi.h -- 2.17.1
