30442571ec
mbm_bw_count() is only called by the mbm_handle_overflow() worker once a second. It reads the hardware register, calculates the bandwidth and updates m->prev_bw_msr which is used to hold the previous hardware register value. Operating directly on hardware register values makes it difficult to make this code architecture independent, so that it can be moved to /fs/, making the mba_sc feature something resctrl supports with no additional support from the architecture. Prior to calling mbm_bw_count(), mbm_update() reads from the same hardware register using __mon_event_count(). Change mbm_bw_count() to use the current chunks value most recently saved by __mon_event_count(). This removes an extra call to __rmid_read(). Instead of using m->prev_msr to calculate the number of chunks seen, use the rr->val that was updated by __mon_event_count(). This removes an extra call to mbm_overflow_count() and get_corrected_mbm_count(). Calculating bandwidth like this means mbm_bw_count() no longer operates on hardware register values directly. Signed-off-by: James Morse <james.morse@arm.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Jamie Iles <quic_jiles@quicinc.com> Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com> Tested-by: Xin Hao <xhao@linux.alibaba.com> Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com> Tested-by: Cristian Marussi <cristian.marussi@arm.com> Link: https://lore.kernel.org/r/20220902154829.30399-13-james.morse@arm.com