On Sat, Dec 19, 2020 at 6:21 AM srinivas pandruvada <srinivas.pandruv...@linux.intel.com> wrote: > > On Thu, 2020-12-17 at 20:17 +0100, Rafael J. Wysocki wrote: > > From: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > > > > When turbo has been disabled by the BIOS, but HWP_CAP.GUARANTEED is > > changed later, user space may want to take advantage of this > > increased > > guaranteed performance. > > > > HWP_CAP.GUARANTEED is not a static value. It can be adjusted by an > > out-of-band agent or during an Intel Speed Select performance level > > change. The HWP_CAP.MAX is still the maximum achievable performance > > with turbo disabled by the BIOS, so HWP_CAP.GUARANTEED can still > > change as long as it remains less than or equal to HWP_CAP.MAX. > > > > When HWP_CAP.GUARANTEED is changed, the sysfs base_frequency > > attribute shows the most recent guaranteed frequency value. This > > attribute can be used by user space software to update the scaling > > min/max limits of the CPU. > > > > Currently, the ->setpolicy() callback already uses the latest > > HWP_CAP values when setting HWP_REQ, but the ->verify() callback will > > restrict the user settings to the to old guaranteed performance value > > which prevents user space from making use of the extra CPU capacity > > theoretically available to it after increasing HWP_CAP.GUARANTEED. > > > > To address this, read HWP_CAP in intel_pstate_verify_cpu_policy() > > to obtain the maximum P-state that can be used and use that to > > confine the policy max limit instead of using the cached and > > possibly stale pstate.max_freq value for this purpose. > > > > For consistency, update intel_pstate_update_perf_limits() to use the > > maximum available P-state returned by intel_pstate_get_hwp_max() to > > compute the maximum frequency instead of using the return value of > > intel_pstate_get_max_freq() which, again, may be stale. > > > > This issue is a side-effect of fixing the scaling frequency limits in > > commit eacc9c5a927e ("cpufreq: intel_pstate: Fix > > intel_pstate_get_hwp_max() > > for turbo disabled") which currected > corrected
Right, thanks!