1 // SPDX-License-Identifier: GPL-2.0-only
3 * Resource Director Technology(RDT)
6 * Copyright (C) 2017 Intel Corporation
9 * Vikas Shivappa <vikas.shivappa@intel.com>
11 * This replaces the cqm.c based on perf but we reuse a lot of
12 * code and datastructures originally from Peter Zijlstra and Matt Fleming.
14 * More information about RDT be found in the Intel (R) x86 Architecture
15 * Software Developer Manual June 2016, volume 3, section 17.17.
18 #include <linux/module.h>
19 #include <linux/slab.h>
20 #include <asm/cpu_device_id.h>
26 struct list_head list;
30 * @rmid_free_lru A least recently used list of free RMIDs
31 * These RMIDs are guaranteed to have an occupancy less than the
34 static LIST_HEAD(rmid_free_lru);
37 * @rmid_limbo_count count of currently unused but (potentially)
39 * This counts RMIDs that no one is currently using but that
40 * may have a occupancy value > intel_cqm_threshold. User can change
41 * the threshold occupancy value.
43 static unsigned int rmid_limbo_count;
46 * @rmid_entry - The entry in the limbo and free lists.
48 static struct rmid_entry *rmid_ptrs;
51 * Global boolean for rdt_monitor which is true if any
52 * resource monitoring is enabled.
57 * Global to indicate which monitoring events are enabled.
59 unsigned int rdt_mon_features;
62 * This is the threshold cache occupancy at which we will consider an
63 * RMID available for re-allocation.
65 unsigned int resctrl_cqm_threshold;
67 #define CF(cf) ((unsigned long)(1048576 * (cf) + 0.5))
70 * The correction factor table is documented in Documentation/x86/resctrl.rst.
71 * If rmid > rmid threshold, MBM total and local values should be multiplied
72 * by the correction factor.
74 * The original table is modified for better code:
76 * 1. The threshold 0 is changed to rmid count - 1 so don't do correction
78 * 2. MBM total and local correction table indexed by core counter which is
79 * equal to (x86_cache_max_rmid + 1) / 8 - 1 and is from 0 up to 27.
80 * 3. The correction factor is normalized to 2^20 (1048576) so it's faster
81 * to calculate corrected value by shifting:
82 * corrected_value = (original_value * correction_factor) >> 20
84 static const struct mbm_correction_factor_table {
87 } mbm_cf_table[] __initconst = {
118 static u32 mbm_cf_rmidthreshold __read_mostly = UINT_MAX;
119 static u64 mbm_cf __read_mostly;
121 static inline u64 get_corrected_mbm_count(u32 rmid, unsigned long val)
123 /* Correct MBM value. */
124 if (rmid > mbm_cf_rmidthreshold)
125 val = (val * mbm_cf) >> 20;
130 static inline struct rmid_entry *__rmid_entry(u32 rmid)
132 struct rmid_entry *entry;
134 entry = &rmid_ptrs[rmid];
135 WARN_ON(entry->rmid != rmid);
140 static u64 __rmid_read(u32 rmid, u32 eventid)
145 * As per the SDM, when IA32_QM_EVTSEL.EvtID (bits 7:0) is configured
146 * with a valid event code for supported resource type and the bits
147 * IA32_QM_EVTSEL.RMID (bits 41:32) are configured with valid RMID,
148 * IA32_QM_CTR.data (bits 61:0) reports the monitored data.
149 * IA32_QM_CTR.Error (bit 63) and IA32_QM_CTR.Unavailable (bit 62)
152 wrmsr(MSR_IA32_QM_EVTSEL, eventid, rmid);
153 rdmsrl(MSR_IA32_QM_CTR, val);
158 static bool rmid_dirty(struct rmid_entry *entry)
160 u64 val = __rmid_read(entry->rmid, QOS_L3_OCCUP_EVENT_ID);
162 return val >= resctrl_cqm_threshold;
166 * Check the RMIDs that are marked as busy for this domain. If the
167 * reported LLC occupancy is below the threshold clear the busy bit and
168 * decrement the count. If the busy count gets to zero on an RMID, we
171 void __check_limbo(struct rdt_domain *d, bool force_free)
173 struct rmid_entry *entry;
174 struct rdt_resource *r;
175 u32 crmid = 1, nrmid;
177 r = &rdt_resources_all[RDT_RESOURCE_L3];
180 * Skip RMID 0 and start from RMID 1 and check all the RMIDs that
181 * are marked as busy for occupancy < threshold. If the occupancy
182 * is less than the threshold decrement the busy counter of the
183 * RMID and move it to the free list when the counter reaches 0.
186 nrmid = find_next_bit(d->rmid_busy_llc, r->num_rmid, crmid);
187 if (nrmid >= r->num_rmid)
190 entry = __rmid_entry(nrmid);
191 if (force_free || !rmid_dirty(entry)) {
192 clear_bit(entry->rmid, d->rmid_busy_llc);
193 if (!--entry->busy) {
195 list_add_tail(&entry->list, &rmid_free_lru);
202 bool has_busy_rmid(struct rdt_resource *r, struct rdt_domain *d)
204 return find_first_bit(d->rmid_busy_llc, r->num_rmid) != r->num_rmid;
208 * As of now the RMIDs allocation is global.
209 * However we keep track of which packages the RMIDs
210 * are used to optimize the limbo list management.
214 struct rmid_entry *entry;
216 lockdep_assert_held(&rdtgroup_mutex);
218 if (list_empty(&rmid_free_lru))
219 return rmid_limbo_count ? -EBUSY : -ENOSPC;
221 entry = list_first_entry(&rmid_free_lru,
222 struct rmid_entry, list);
223 list_del(&entry->list);
228 static void add_rmid_to_limbo(struct rmid_entry *entry)
230 struct rdt_resource *r;
231 struct rdt_domain *d;
235 r = &rdt_resources_all[RDT_RESOURCE_L3];
239 list_for_each_entry(d, &r->domains, list) {
240 if (cpumask_test_cpu(cpu, &d->cpu_mask)) {
241 val = __rmid_read(entry->rmid, QOS_L3_OCCUP_EVENT_ID);
242 if (val <= resctrl_cqm_threshold)
247 * For the first limbo RMID in the domain,
248 * setup up the limbo worker.
250 if (!has_busy_rmid(r, d))
251 cqm_setup_limbo_handler(d, CQM_LIMBOCHECK_INTERVAL);
252 set_bit(entry->rmid, d->rmid_busy_llc);
260 list_add_tail(&entry->list, &rmid_free_lru);
263 void free_rmid(u32 rmid)
265 struct rmid_entry *entry;
270 lockdep_assert_held(&rdtgroup_mutex);
272 entry = __rmid_entry(rmid);
274 if (is_llc_occupancy_enabled())
275 add_rmid_to_limbo(entry);
277 list_add_tail(&entry->list, &rmid_free_lru);
280 static u64 mbm_overflow_count(u64 prev_msr, u64 cur_msr, unsigned int width)
282 u64 shift = 64 - width, chunks;
284 chunks = (cur_msr << shift) - (prev_msr << shift);
285 return chunks >>= shift;
288 static u64 __mon_event_count(u32 rmid, struct rmid_read *rr)
293 tval = __rmid_read(rmid, rr->evtid);
294 if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL)) {
298 case QOS_L3_OCCUP_EVENT_ID:
301 case QOS_L3_MBM_TOTAL_EVENT_ID:
302 m = &rr->d->mbm_total[rmid];
304 case QOS_L3_MBM_LOCAL_EVENT_ID:
305 m = &rr->d->mbm_local[rmid];
310 memset(m, 0, sizeof(struct mbm_state));
311 m->prev_bw_msr = m->prev_msr = tval;
315 chunks = mbm_overflow_count(m->prev_msr, tval, rr->r->mbm_width);
319 rr->val += get_corrected_mbm_count(rmid, m->chunks);
325 * Supporting function to calculate the memory bandwidth
326 * and delta bandwidth in MBps.
328 static void mbm_bw_count(u32 rmid, struct rmid_read *rr)
330 struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3];
331 struct mbm_state *m = &rr->d->mbm_local[rmid];
332 u64 tval, cur_bw, chunks;
334 tval = __rmid_read(rmid, rr->evtid);
335 if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL))
338 chunks = mbm_overflow_count(m->prev_bw_msr, tval, rr->r->mbm_width);
339 cur_bw = (get_corrected_mbm_count(rmid, chunks) * r->mon_scale) >> 20;
342 m->delta_bw = abs(cur_bw - m->prev_bw);
343 m->delta_comp = false;
345 m->prev_bw_msr = tval;
349 * This is called via IPI to read the CQM/MBM counters
352 void mon_event_count(void *info)
354 struct rdtgroup *rdtgrp, *entry;
355 struct rmid_read *rr = info;
356 struct list_head *head;
361 ret_val = __mon_event_count(rdtgrp->mon.rmid, rr);
364 * For Ctrl groups read data from child monitor groups and
365 * add them together. Count events which are read successfully.
366 * Discard the rmid_read's reporting errors.
368 head = &rdtgrp->mon.crdtgrp_list;
370 if (rdtgrp->type == RDTCTRL_GROUP) {
371 list_for_each_entry(entry, head, mon.crdtgrp_list) {
372 if (__mon_event_count(entry->mon.rmid, rr) == 0)
377 /* Report error if none of rmid_reads are successful */
383 * Feedback loop for MBA software controller (mba_sc)
385 * mba_sc is a feedback loop where we periodically read MBM counters and
386 * adjust the bandwidth percentage values via the IA32_MBA_THRTL_MSRs so
389 * current bandwidth(cur_bw) < user specified bandwidth(user_bw)
391 * This uses the MBM counters to measure the bandwidth and MBA throttle
392 * MSRs to control the bandwidth for a particular rdtgrp. It builds on the
393 * fact that resctrl rdtgroups have both monitoring and control.
395 * The frequency of the checks is 1s and we just tag along the MBM overflow
396 * timer. Having 1s interval makes the calculation of bandwidth simpler.
398 * Although MBA's goal is to restrict the bandwidth to a maximum, there may
399 * be a need to increase the bandwidth to avoid unnecessarily restricting
400 * the L2 <-> L3 traffic.
402 * Since MBA controls the L2 external bandwidth where as MBM measures the
403 * L3 external bandwidth the following sequence could lead to such a
406 * Consider an rdtgroup which had high L3 <-> memory traffic in initial
407 * phases -> mba_sc kicks in and reduced bandwidth percentage values -> but
408 * after some time rdtgroup has mostly L2 <-> L3 traffic.
410 * In this case we may restrict the rdtgroup's L2 <-> L3 traffic as its
411 * throttle MSRs already have low percentage values. To avoid
412 * unnecessarily restricting such rdtgroups, we also increase the bandwidth.
414 static void update_mba_bw(struct rdtgroup *rgrp, struct rdt_domain *dom_mbm)
416 u32 closid, rmid, cur_msr, cur_msr_val, new_msr_val;
417 struct mbm_state *pmbm_data, *cmbm_data;
418 u32 cur_bw, delta_bw, user_bw;
419 struct rdt_resource *r_mba;
420 struct rdt_domain *dom_mba;
421 struct list_head *head;
422 struct rdtgroup *entry;
424 if (!is_mbm_local_enabled())
427 r_mba = &rdt_resources_all[RDT_RESOURCE_MBA];
428 closid = rgrp->closid;
429 rmid = rgrp->mon.rmid;
430 pmbm_data = &dom_mbm->mbm_local[rmid];
432 dom_mba = get_domain_from_cpu(smp_processor_id(), r_mba);
434 pr_warn_once("Failure to get domain for MBA update\n");
438 cur_bw = pmbm_data->prev_bw;
439 user_bw = dom_mba->mbps_val[closid];
440 delta_bw = pmbm_data->delta_bw;
441 cur_msr_val = dom_mba->ctrl_val[closid];
444 * For Ctrl groups read data from child monitor groups.
446 head = &rgrp->mon.crdtgrp_list;
447 list_for_each_entry(entry, head, mon.crdtgrp_list) {
448 cmbm_data = &dom_mbm->mbm_local[entry->mon.rmid];
449 cur_bw += cmbm_data->prev_bw;
450 delta_bw += cmbm_data->delta_bw;
454 * Scale up/down the bandwidth linearly for the ctrl group. The
455 * bandwidth step is the bandwidth granularity specified by the
458 * The delta_bw is used when increasing the bandwidth so that we
459 * dont alternately increase and decrease the control values
462 * For ex: consider cur_bw = 90MBps, user_bw = 100MBps and if
463 * bandwidth step is 20MBps(> user_bw - cur_bw), we would keep
464 * switching between 90 and 110 continuously if we only check
467 if (cur_msr_val > r_mba->membw.min_bw && user_bw < cur_bw) {
468 new_msr_val = cur_msr_val - r_mba->membw.bw_gran;
469 } else if (cur_msr_val < MAX_MBA_BW &&
470 (user_bw > (cur_bw + delta_bw))) {
471 new_msr_val = cur_msr_val + r_mba->membw.bw_gran;
476 cur_msr = r_mba->msr_base + closid;
477 wrmsrl(cur_msr, delay_bw_map(new_msr_val, r_mba));
478 dom_mba->ctrl_val[closid] = new_msr_val;
481 * Delta values are updated dynamically package wise for each
482 * rdtgrp every time the throttle MSR changes value.
484 * This is because (1)the increase in bandwidth is not perfectly
485 * linear and only "approximately" linear even when the hardware
486 * says it is linear.(2)Also since MBA is a core specific
487 * mechanism, the delta values vary based on number of cores used
490 pmbm_data->delta_comp = true;
491 list_for_each_entry(entry, head, mon.crdtgrp_list) {
492 cmbm_data = &dom_mbm->mbm_local[entry->mon.rmid];
493 cmbm_data->delta_comp = true;
497 static void mbm_update(struct rdt_resource *r, struct rdt_domain *d, int rmid)
506 * This is protected from concurrent reads from user
507 * as both the user and we hold the global mutex.
509 if (is_mbm_total_enabled()) {
510 rr.evtid = QOS_L3_MBM_TOTAL_EVENT_ID;
511 __mon_event_count(rmid, &rr);
513 if (is_mbm_local_enabled()) {
514 rr.evtid = QOS_L3_MBM_LOCAL_EVENT_ID;
515 __mon_event_count(rmid, &rr);
518 * Call the MBA software controller only for the
519 * control groups and when user has enabled
520 * the software controller explicitly.
523 mbm_bw_count(rmid, &rr);
528 * Handler to scan the limbo list and move the RMIDs
529 * to free list whose occupancy < threshold_occupancy.
531 void cqm_handle_limbo(struct work_struct *work)
533 unsigned long delay = msecs_to_jiffies(CQM_LIMBOCHECK_INTERVAL);
534 int cpu = smp_processor_id();
535 struct rdt_resource *r;
536 struct rdt_domain *d;
538 mutex_lock(&rdtgroup_mutex);
540 r = &rdt_resources_all[RDT_RESOURCE_L3];
541 d = container_of(work, struct rdt_domain, cqm_limbo.work);
543 __check_limbo(d, false);
545 if (has_busy_rmid(r, d))
546 schedule_delayed_work_on(cpu, &d->cqm_limbo, delay);
548 mutex_unlock(&rdtgroup_mutex);
551 void cqm_setup_limbo_handler(struct rdt_domain *dom, unsigned long delay_ms)
553 unsigned long delay = msecs_to_jiffies(delay_ms);
556 cpu = cpumask_any(&dom->cpu_mask);
557 dom->cqm_work_cpu = cpu;
559 schedule_delayed_work_on(cpu, &dom->cqm_limbo, delay);
562 void mbm_handle_overflow(struct work_struct *work)
564 unsigned long delay = msecs_to_jiffies(MBM_OVERFLOW_INTERVAL);
565 struct rdtgroup *prgrp, *crgrp;
566 int cpu = smp_processor_id();
567 struct list_head *head;
568 struct rdt_resource *r;
569 struct rdt_domain *d;
571 mutex_lock(&rdtgroup_mutex);
573 if (!static_branch_likely(&rdt_mon_enable_key))
576 r = &rdt_resources_all[RDT_RESOURCE_L3];
577 d = container_of(work, struct rdt_domain, mbm_over.work);
579 list_for_each_entry(prgrp, &rdt_all_groups, rdtgroup_list) {
580 mbm_update(r, d, prgrp->mon.rmid);
582 head = &prgrp->mon.crdtgrp_list;
583 list_for_each_entry(crgrp, head, mon.crdtgrp_list)
584 mbm_update(r, d, crgrp->mon.rmid);
587 update_mba_bw(prgrp, d);
590 schedule_delayed_work_on(cpu, &d->mbm_over, delay);
593 mutex_unlock(&rdtgroup_mutex);
596 void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms)
598 unsigned long delay = msecs_to_jiffies(delay_ms);
601 if (!static_branch_likely(&rdt_mon_enable_key))
603 cpu = cpumask_any(&dom->cpu_mask);
604 dom->mbm_work_cpu = cpu;
605 schedule_delayed_work_on(cpu, &dom->mbm_over, delay);
608 static int dom_data_init(struct rdt_resource *r)
610 struct rmid_entry *entry = NULL;
613 nr_rmids = r->num_rmid;
614 rmid_ptrs = kcalloc(nr_rmids, sizeof(struct rmid_entry), GFP_KERNEL);
618 for (i = 0; i < nr_rmids; i++) {
619 entry = &rmid_ptrs[i];
620 INIT_LIST_HEAD(&entry->list);
623 list_add_tail(&entry->list, &rmid_free_lru);
627 * RMID 0 is special and is always allocated. It's used for all
628 * tasks that are not monitored.
630 entry = __rmid_entry(0);
631 list_del(&entry->list);
636 static struct mon_evt llc_occupancy_event = {
637 .name = "llc_occupancy",
638 .evtid = QOS_L3_OCCUP_EVENT_ID,
641 static struct mon_evt mbm_total_event = {
642 .name = "mbm_total_bytes",
643 .evtid = QOS_L3_MBM_TOTAL_EVENT_ID,
646 static struct mon_evt mbm_local_event = {
647 .name = "mbm_local_bytes",
648 .evtid = QOS_L3_MBM_LOCAL_EVENT_ID,
652 * Initialize the event list for the resource.
654 * Note that MBM events are also part of RDT_RESOURCE_L3 resource
655 * because as per the SDM the total and local memory bandwidth
656 * are enumerated as part of L3 monitoring.
658 static void l3_mon_evt_init(struct rdt_resource *r)
660 INIT_LIST_HEAD(&r->evt_list);
662 if (is_llc_occupancy_enabled())
663 list_add_tail(&llc_occupancy_event.list, &r->evt_list);
664 if (is_mbm_total_enabled())
665 list_add_tail(&mbm_total_event.list, &r->evt_list);
666 if (is_mbm_local_enabled())
667 list_add_tail(&mbm_local_event.list, &r->evt_list);
670 int rdt_get_mon_l3_config(struct rdt_resource *r)
672 unsigned int mbm_offset = boot_cpu_data.x86_cache_mbm_width_offset;
673 unsigned int cl_size = boot_cpu_data.x86_cache_size;
676 r->mon_scale = boot_cpu_data.x86_cache_occ_scale;
677 r->num_rmid = boot_cpu_data.x86_cache_max_rmid + 1;
678 r->mbm_width = MBM_CNTR_WIDTH_BASE;
680 if (mbm_offset > 0 && mbm_offset <= MBM_CNTR_WIDTH_OFFSET_MAX)
681 r->mbm_width += mbm_offset;
682 else if (mbm_offset > MBM_CNTR_WIDTH_OFFSET_MAX)
683 pr_warn("Ignoring impossible MBM counter offset\n");
686 * A reasonable upper limit on the max threshold is the number
687 * of lines tagged per RMID if all RMIDs have the same number of
688 * lines tagged in the LLC.
690 * For a 35MB LLC and 56 RMIDs, this is ~1.8% of the LLC.
692 resctrl_cqm_threshold = cl_size * 1024 / r->num_rmid;
694 /* h/w works in units of "boot_cpu_data.x86_cache_occ_scale" */
695 resctrl_cqm_threshold /= r->mon_scale;
697 ret = dom_data_init(r);
703 r->mon_capable = true;
704 r->mon_enabled = true;
709 void __init intel_rdt_mbm_apply_quirk(void)
713 cf_index = (boot_cpu_data.x86_cache_max_rmid + 1) / 8 - 1;
714 if (cf_index >= ARRAY_SIZE(mbm_cf_table)) {
715 pr_info("No MBM correction factor available\n");
719 mbm_cf_rmidthreshold = mbm_cf_table[cf_index].rmidthreshold;
720 mbm_cf = mbm_cf_table[cf_index].cf;