x86/resctrl: Prevent NULL pointer dereference when local MBM is disabled

[thirdparty/kernel/stable.git] / 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
 * and delta bandwidth in MBps.
 */
static void mbm_bw_count(u32 rmid, struct rmid_read *rr)
{
        struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3];
        struct mbm_state *m = &rr->d->mbm_local[rmid];
        u64 tval, cur_bw, chunks;

        tval = __rmid_read(rmid, rr->evtid);
        if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL))
                return;

        chunks = mbm_overflow_count(m->prev_bw_msr, tval);
        m->chunks_bw += chunks;
        m->chunks = m->chunks_bw;
        cur_bw = (chunks * r->mon_scale) >> 20;

        if (m->delta_comp)
                m->delta_bw = abs(cur_bw - m->prev_bw);
        m->delta_comp = false;
        m->prev_bw = cur_bw;
        m->prev_bw_msr = tval;
}

/*
 * This is called via IPI to read the CQM/MBM counters
 * on a domain.
 */
void mon_event_count(void *info)
{
        struct rdtgroup *rdtgrp, *entry;
        struct rmid_read *rr = info;
        struct list_head *head;

        rdtgrp = rr->rgrp;

        if (__mon_event_count(rdtgrp->mon.rmid, rr))
                return;

        /*
         * For Ctrl groups read data from child monitor groups.
         */
        head = &rdtgrp->mon.crdtgrp_list;

        if (rdtgrp->type == RDTCTRL_GROUP) {
                list_for_each_entry(entry, head, mon.crdtgrp_list) {
                        if (__mon_event_count(entry->mon.rmid, rr))
                                return;
                }
        }
}

/*
 * Feedback loop for MBA software controller (mba_sc)
 *
 * mba_sc is a feedback loop where we periodically read MBM counters and
 * adjust the bandwidth percentage values via the IA32_MBA_THRTL_MSRs so
 * that:
 *
 *   current bandwdith(cur_bw) < user specified bandwidth(user_bw)
 *
 * This uses the MBM counters to measure the bandwidth and MBA throttle
 * MSRs to control the bandwidth for a particular rdtgrp. It builds on the
 * fact that resctrl rdtgroups have both monitoring and control.
 *
 * The frequency of the checks is 1s and we just tag along the MBM overflow
 * timer. Having 1s interval makes the calculation of bandwidth simpler.
 *
 * Although MBA's goal is to restrict the bandwidth to a maximum, there may
 * be a need to increase the bandwidth to avoid uncecessarily restricting
 * the L2 <-> L3 traffic.
 *
 * Since MBA controls the L2 external bandwidth where as MBM measures the
 * L3 external bandwidth the following sequence could lead to such a
 * situation.
 *
 * Consider an rdtgroup which had high L3 <-> memory traffic in initial
 * phases -> mba_sc kicks in and reduced bandwidth percentage values -> but
 * after some time rdtgroup has mostly L2 <-> L3 traffic.
 *
 * In this case we may restrict the rdtgroup's L2 <-> L3 traffic as its
 * throttle MSRs already have low percentage values.  To avoid
 * unnecessarily restricting such rdtgroups, we also increase the bandwidth.
 */
static void update_mba_bw(struct rdtgroup *rgrp, struct rdt_domain *dom_mbm)
{
        u32 closid, rmid, cur_msr, cur_msr_val, new_msr_val;
        struct mbm_state *pmbm_data, *cmbm_data;
        u32 cur_bw, delta_bw, user_bw;
        struct rdt_resource *r_mba;
        struct rdt_domain *dom_mba;
        struct list_head *head;
        struct rdtgroup *entry;

        if (!is_mbm_local_enabled())
                return;

        r_mba = &rdt_resources_all[RDT_RESOURCE_MBA];
        closid = rgrp->closid;
        rmid = rgrp->mon.rmid;
        pmbm_data = &dom_mbm->mbm_local[rmid];

        dom_mba = get_domain_from_cpu(smp_processor_id(), r_mba);
        if (!dom_mba) {
                pr_warn_once("Failure to get domain for MBA update\n");
                return;
        }

        cur_bw = pmbm_data->prev_bw;
        user_bw = dom_mba->mbps_val[closid];
        delta_bw = pmbm_data->delta_bw;
        cur_msr_val = dom_mba->ctrl_val[closid];

        /*
         * For Ctrl groups read data from child monitor groups.
         */
        head = &rgrp->mon.crdtgrp_list;
        list_for_each_entry(entry, head, mon.crdtgrp_list) {
                cmbm_data = &dom_mbm->mbm_local[entry->mon.rmid];
                cur_bw += cmbm_data->prev_bw;
                delta_bw += cmbm_data->delta_bw;
        }

        /*
         * Scale up/down the bandwidth linearly for the ctrl group.  The
         * bandwidth step is the bandwidth granularity specified by the
         * hardware.
         *
         * The delta_bw is used when increasing the bandwidth so that we
         * dont alternately increase and decrease the control values
         * continuously.
         *
         * For ex: consider cur_bw = 90MBps, user_bw = 100MBps and if
         * bandwidth step is 20MBps(> user_bw - cur_bw), we would keep
         * switching between 90 and 110 continuously if we only check
         * cur_bw < user_bw.
         */
        if (cur_msr_val > r_mba->membw.min_bw && user_bw < cur_bw) {
                new_msr_val = cur_msr_val - r_mba->membw.bw_gran;
        } else if (cur_msr_val < MAX_MBA_BW &&
                   (user_bw > (cur_bw + delta_bw))) {
                new_msr_val = cur_msr_val + r_mba->membw.bw_gran;
        } else {
                return;
        }

        cur_msr = r_mba->msr_base + closid;
        wrmsrl(cur_msr, delay_bw_map(new_msr_val, r_mba));
        dom_mba->ctrl_val[closid] = new_msr_val;

        /*
         * Delta values are updated dynamically package wise for each
         * rdtgrp everytime the throttle MSR changes value.
         *
         * This is because (1)the increase in bandwidth is not perfectly
         * linear and only "approximately" linear even when the hardware
         * says it is linear.(2)Also since MBA is a core specific
         * mechanism, the delta values vary based on number of cores used
         * by the rdtgrp.
         */
        pmbm_data->delta_comp = true;
        list_for_each_entry(entry, head, mon.crdtgrp_list) {
                cmbm_data = &dom_mbm->mbm_local[entry->mon.rmid];
                cmbm_data->delta_comp = true;
        }
}

static void mbm_update(struct rdt_domain *d, int rmid)
{
        struct rmid_read rr;

        rr.first = false;
        rr.d = d;

        /*
         * This is protected from concurrent reads from user
         * as both the user and we hold the global mutex.
         */
        if (is_mbm_total_enabled()) {
                rr.evtid = QOS_L3_MBM_TOTAL_EVENT_ID;
                __mon_event_count(rmid, &rr);
        }
        if (is_mbm_local_enabled()) {
                rr.evtid = QOS_L3_MBM_LOCAL_EVENT_ID;

                /*
                 * Call the MBA software controller only for the
                 * control groups and when user has enabled
                 * the software controller explicitly.
                 */
                if (!is_mba_sc(NULL))
                        __mon_event_count(rmid, &rr);
                else
                        mbm_bw_count(rmid, &rr);
        }
}

/*
 * Handler to scan the limbo list and move the RMIDs
 * to free list whose occupancy < threshold_occupancy.
 */
void cqm_handle_limbo(struct work_struct *work)
{
        unsigned long delay = msecs_to_jiffies(CQM_LIMBOCHECK_INTERVAL);
        int cpu = smp_processor_id();
        struct rdt_resource *r;
        struct rdt_domain *d;

        mutex_lock(&rdtgroup_mutex);

        r = &rdt_resources_all[RDT_RESOURCE_L3];
        d = get_domain_from_cpu(cpu, r);

        if (!d) {
                pr_warn_once("Failure to get domain for limbo worker\n");
                goto out_unlock;
        }

        __check_limbo(d, false);

        if (has_busy_rmid(r, d))
                schedule_delayed_work_on(cpu, &d->cqm_limbo, delay);

out_unlock:
        mutex_unlock(&rdtgroup_mutex);
}

void cqm_setup_limbo_handler(struct rdt_domain *dom, unsigned long delay_ms)
{
        unsigned long delay = msecs_to_jiffies(delay_ms);
        int cpu;

        cpu = cpumask_any(&dom->cpu_mask);
        dom->cqm_work_cpu = cpu;

        schedule_delayed_work_on(cpu, &dom->cqm_limbo, delay);
}

void mbm_handle_overflow(struct work_struct *work)
{
        unsigned long delay = msecs_to_jiffies(MBM_OVERFLOW_INTERVAL);
        struct rdtgroup *prgrp, *crgrp;
        int cpu = smp_processor_id();
        struct list_head *head;
        struct rdt_domain *d;

        mutex_lock(&rdtgroup_mutex);

        if (!static_branch_likely(&rdt_enable_key))
                goto out_unlock;

        d = get_domain_from_cpu(cpu, &rdt_resources_all[RDT_RESOURCE_L3]);
        if (!d)
                goto out_unlock;

        list_for_each_entry(prgrp, &rdt_all_groups, rdtgroup_list) {
                mbm_update(d, prgrp->mon.rmid);

                head = &prgrp->mon.crdtgrp_list;
                list_for_each_entry(crgrp, head, mon.crdtgrp_list)
                        mbm_update(d, crgrp->mon.rmid);

                if (is_mba_sc(NULL))
                        update_mba_bw(prgrp, d);
        }

        schedule_delayed_work_on(cpu, &d->mbm_over, delay);

out_unlock:
        mutex_unlock(&rdtgroup_mutex);
}

void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms)
{
        unsigned long delay = msecs_to_jiffies(delay_ms);
        int cpu;

        if (!static_branch_likely(&rdt_enable_key))
                return;
        cpu = cpumask_any(&dom->cpu_mask);
        dom->mbm_work_cpu = cpu;
        schedule_delayed_work_on(cpu, &dom->mbm_over, delay);
}

static int dom_data_init(struct rdt_resource *r)
{
        struct rmid_entry *entry = NULL;
        int i, nr_rmids;

        nr_rmids = r->num_rmid;
        rmid_ptrs = kcalloc(nr_rmids, sizeof(struct rmid_entry), GFP_KERNEL);
        if (!rmid_ptrs)
                return -ENOMEM;

        for (i = 0; i < nr_rmids; i++) {
                entry = &rmid_ptrs[i];
                INIT_LIST_HEAD(&entry->list);

                entry->rmid = i;
                list_add_tail(&entry->list, &rmid_free_lru);
        }

        /*
         * RMID 0 is special and is always allocated. It's used for all
         * tasks that are not monitored.
         */
        entry = __rmid_entry(0);
        list_del(&entry->list);

        return 0;
}

static struct mon_evt llc_occupancy_event = {
        .name           = "llc_occupancy",
        .evtid          = QOS_L3_OCCUP_EVENT_ID,
};

static struct mon_evt mbm_total_event = {
        .name           = "mbm_total_bytes",
        .evtid          = QOS_L3_MBM_TOTAL_EVENT_ID,
};

static struct mon_evt mbm_local_event = {
        .name           = "mbm_local_bytes",
        .evtid          = QOS_L3_MBM_LOCAL_EVENT_ID,
};

/*
 * Initialize the event list for the resource.
 *
 * Note that MBM events are also part of RDT_RESOURCE_L3 resource
 * because as per the SDM the total and local memory bandwidth
 * are enumerated as part of L3 monitoring.
 */
static void l3_mon_evt_init(struct rdt_resource *r)
{
        INIT_LIST_HEAD(&r->evt_list);

        if (is_llc_occupancy_enabled())
                list_add_tail(&llc_occupancy_event.list, &r->evt_list);
        if (is_mbm_total_enabled())
                list_add_tail(&mbm_total_event.list, &r->evt_list);
        if (is_mbm_local_enabled())
                list_add_tail(&mbm_local_event.list, &r->evt_list);
}

int rdt_get_mon_l3_config(struct rdt_resource *r)
{
        unsigned int cl_size = boot_cpu_data.x86_cache_size;
        int ret;

        r->mon_scale = boot_cpu_data.x86_cache_occ_scale;
        r->num_rmid = boot_cpu_data.x86_cache_max_rmid + 1;

        /*
         * A reasonable upper limit on the max threshold is the number
         * of lines tagged per RMID if all RMIDs have the same number of
         * lines tagged in the LLC.
         *
         * For a 35MB LLC and 56 RMIDs, this is ~1.8% of the LLC.
         */
        resctrl_cqm_threshold = cl_size * 1024 / r->num_rmid;

        /* h/w works in units of "boot_cpu_data.x86_cache_occ_scale" */
        resctrl_cqm_threshold /= r->mon_scale;

        ret = dom_data_init(r);
        if (ret)
                return ret;

        l3_mon_evt_init(r);

        r->mon_capable = true;
        r->mon_enabled = true;

        return 0;
}