path: root/arch/x86/kernel/cpu/resctrl/monitor.c

/*
 * Resource Director Technology(RDT)
 * - Monitoring code
 *
 * Copyright (C) 2017 Intel Corporation
 *
 * Author:
 *    Vikas Shivappa <vikas.shivappa@intel.com>
 *
 * This replaces the cqm.c based on perf but we reuse a lot of
 * code and datastructures originally from Peter Zijlstra and Matt Fleming.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * More information about RDT be found in the Intel (R) x86 Architecture
 * Software Developer Manual June 2016, volume 3, section 17.17.
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <asm/cpu_device_id.h>
#include "internal.h"

struct rmid_entry {
	u32				rmid;
	int				busy;
	struct list_head		list;
};

/**
 * @rmid_free_lru    A least recently used list of free RMIDs
 *     These RMIDs are guaranteed to have an occupancy less than the
 *     threshold occupancy
 */
static LIST_HEAD(rmid_free_lru);

/**
 * @rmid_limbo_count     count of currently unused but (potentially)
 *     dirty RMIDs.
 *     This counts RMIDs that no one is currently using but that
 *     may have a occupancy value > intel_cqm_threshold. User can change
 *     the threshold occupancy value.
 */
static unsigned int rmid_limbo_count;

/**
 * @rmid_entry - The entry in the limbo and free lists.
 */
static struct rmid_entry	*rmid_ptrs;

/*
 * Global boolean for rdt_monitor which is true if any
 * resource monitoring is enabled.
 */
bool rdt_mon_capable;

/*
 * Global to indicate which monitoring events are enabled.
 */
unsigned int rdt_mon_features;

/*
 * This is the threshold cache occupancy at which we will consider an
 * RMID available for re-allocation.
 */
unsigned int resctrl_cqm_threshold;

static inline struct rmid_entry *__rmid_entry(u32 rmid)
{
	struct rmid_entry *entry;

	entry = &rmid_ptrs[rmid];
	WARN_ON(entry->rmid != rmid);

	return entry;
}

static u64 __rmid_read(u32 rmid, u32 eventid)
{
	u64 val;

	/*
	 * As per the SDM, when IA32_QM_EVTSEL.EvtID (bits 7:0) is configured
	 * with a valid event code for supported resource type and the bits
	 * IA32_QM_EVTSEL.RMID (bits 41:32) are configured with valid RMID,
	 * IA32_QM_CTR.data (bits 61:0) reports the monitored data.
	 * IA32_QM_CTR.Error (bit 63) and IA32_QM_CTR.Unavailable (bit 62)
	 * are error bits.
	 */
	wrmsr(MSR_IA32_QM_EVTSEL, eventid, rmid);
	rdmsrl(MSR_IA32_QM_CTR, val);

	return val;
}

static bool rmid_dirty(struct rmid_entry *entry)
{
	u64 val = __rmid_read(entry->rmid, QOS_L3_OCCUP_EVENT_ID);

	return val >= resctrl_cqm_threshold;
}

/*
 * Check the RMIDs that are marked as busy for this domain. If the
 * reported LLC occupancy is below the threshold clear the busy bit and
 * decrement the count. If the busy count gets to zero on an RMID, we
 * free the RMID
 */
void __check_limbo(struct rdt_domain *d, bool force_free)
{
	struct rmid_entry *entry;
	struct rdt_resource *r;
	u32 crmid = 1, nrmid;

	r = &rdt_resources_all[RDT_RESOURCE_L3];

	/*
	 * Skip RMID 0 and start from RMID 1 and check all the RMIDs that
	 * are marked as busy for occupancy < threshold. If the occupancy
	 * is less than the threshold decrement the busy counter of the
	 * RMID and move it to the free list when the counter reaches 0.
	 */
	for (;;) {
		nrmid = find_next_bit(d->rmid_busy_llc, r->num_rmid, crmid);
		if (nrmid >= r->num_rmid)
			break;

		entry = __rmid_entry(nrmid);
		if (force_free || !rmid_dirty(entry)) {
			clear_bit(entry->rmid, d->rmid_busy_llc);
			if (!--entry->busy) {
				rmid_limbo_count--;
				list_add_tail(&entry->list, &rmid_free_lru);
			}
		}
		crmid = nrmid + 1;
	}
}

bool has_busy_rmid(struct rdt_resource *r, struct rdt_domain *d)
{
	return find_first_bit(d->rmid_busy_llc, r->num_rmid) != r->num_rmid;
}

/*
 * As of now the RMIDs allocation is global.
 * However we keep track of which packages the RMIDs
 * are used to optimize the limbo list management.
 */
int alloc_rmid(void)
{
	struct rmid_entry *entry;

	lockdep_assert_held(&rdtgroup_mutex);

	if (list_empty(&rmid_free_lru))
		return rmid_limbo_count ? -EBUSY : -ENOSPC;

	entry = list_first_entry(&rmid_free_lru,
				 struct rmid_entry, list);
	list_del(&entry->list);

	return entry->rmid;
}

static void add_rmid_to_limbo(struct rmid_entry *entry)
{
	struct rdt_resource *r;
	struct rdt_domain *d;
	int cpu;
	u64 val;

	r = &rdt_resources_all[RDT_RESOURCE_L3];

	entry->busy = 0;
	cpu = get_cpu();
	list_for_each_entry(d, &r->domains, list) {
		if (cpumask_test_cpu(cpu, &d->cpu_mask)) {
			val = __rmid_read(entry->rmid, QOS_L3_OCCUP_EVENT_ID);
			if (val <= resctrl_cqm_threshold)
				continue;
		}

		/*
		 * For the first limbo RMID in the domain,
		 * setup up the limbo worker.
		 */
		if (!has_busy_rmid(r, d))
			cqm_setup_limbo_handler(d, CQM_LIMBOCHECK_INTERVAL);
		set_bit(entry->rmid, d->rmid_busy_llc);
		entry->busy++;
	}
	put_cpu();

	if (entry->busy)
		rmid_limbo_count++;
	else
		list_add_tail(&entry->list, &rmid_free_lru);
}

void free_rmid(u32 rmid)
{
	struct rmid_entry *entry;

	if (!rmid)
		return;

	lockdep_assert_held(&rdtgroup_mutex);

	entry = __rmid_entry(rmid);

	if (is_llc_occupancy_enabled())
		add_rmid_to_limbo(entry);
	else
		list_add_tail(&entry->list, &rmid_free_lru);
}

static u64 mbm_overflow_count(u64 prev_msr, u64 cur_msr)
{
	u64 shift = 64 - MBM_CNTR_WIDTH, chunks;

	chunks = (cur_msr << shift) - (prev_msr << shift);
	return chunks >>= shift;
}

static int __mon_event_count(u32 rmid, struct rmid_read *rr)
{
	struct mbm_state *m;
	u64 chunks, tval;

	tval = __rmid_read(rmid, rr->evtid);
	if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL)) {
		rr->val = tval;
		return -EINVAL;
	}
	switch (rr->evtid) {
	case QOS_L3_OCCUP_EVENT_ID:
		rr->val += tval;
		return 0;
	case QOS_L3_MBM_TOTAL_EVENT_ID:
		m = &rr->d->mbm_total[rmid];
		break;
	case QOS_L3_MBM_LOCAL_EVENT_ID:
		m = &rr->d->mbm_local[rmid];
		break;
	default:
		/*
		 * Code would never reach here because
		 * an invalid event id would fail the __rmid_read.
		 */
		return -EINVAL;
	}

	if (rr->first) {
		memset(m, 0, sizeof(struct mbm_state));
		m->prev_bw_msr = m->prev_msr = tval;
		return 0;
	}

	chunks = mbm_overflow_count(m->prev_msr, tval);
	m->chunks += chunks;
	m->prev_msr = tval;

	rr->val += m->chunks;
	return 0;
}

/*
 * Supporting function to calculate the memory bandwidth
 * an