x86/resctrl: Maintain MBM counter width per resource

The original Memory Bandwidth Monitoring (MBM) architectural
definition defines counters of up to 62 bits in the IA32_QM_CTR MSR,
and the first-generation MBM implementation uses 24 bit counters.
Software is required to poll at 1 second or faster to ensure that
data is retrieved before a counter rollover occurs more than once
under worst conditions.

As system bandwidths scale the software requirement is maintained with
the introduction of a per-resource enumerable MBM counter width.

In preparation for supporting hardware with an enumerable MBM counter
width the current globally static MBM counter width is moved to a
per-resource MBM counter width. Currently initialized to 24 always
to result in no functional change.

In essence there is one function, mbm_overflow_count() that needs to
know the counter width to handle rollovers. The static value
used within mbm_overflow_count() will be replaced with a value
discovered from the hardware. Support for learning the MBM counter
width from hardware is added in the change that follows.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/e36743b9800f16ce600f86b89127391f61261f23.1588715690.git.reinette.chatre@intel.com

diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index 055c861..934c8fb 100644 (file)
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -495,14 +495,16 @@ int rdtgroup_schemata_show(struct kernfs_open_file *of,
        return ret;
 }
 
-void mon_event_read(struct rmid_read *rr, struct rdt_domain *d,
-                   struct rdtgroup *rdtgrp, int evtid, int first)
+void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
+                   struct rdt_domain *d, struct rdtgroup *rdtgrp,
+                   int evtid, int first)
 {
        /*
         * setup the parameters to send to the IPI to read the data.
         */
        rr->rgrp = rdtgrp;
        rr->evtid = evtid;
+       rr->r = r;
        rr->d = d;
        rr->val = 0;
        rr->first = first;
@@ -539,7 +541,7 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
                goto out;
        }
 
-       mon_event_read(&rr, d, rdtgrp, evtid, false);
+       mon_event_read(&rr, r, d, rdtgrp, evtid, false);
 
        if (rr.val & RMID_VAL_ERROR)
                seq_puts(m, "Error\n");

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 3dd13f3..58b002c 100644 (file)
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -87,6 +87,7 @@ union mon_data_bits {
 
 struct rmid_read {
        struct rdtgroup         *rgrp;
+       struct rdt_resource     *r;
        struct rdt_domain       *d;
        int                     evtid;
        bool                    first;
@@ -460,6 +461,7 @@ struct rdt_resource {
        struct list_head        evt_list;
        int                     num_rmid;
        unsigned int            mon_scale;
+       unsigned int            mbm_width;
        unsigned long           fflags;
 };
 
@@ -587,8 +589,9 @@ void rmdir_mondata_subdir_allrdtgrp(struct rdt_resource *r,
                                    unsigned int dom_id);
 void mkdir_mondata_subdir_allrdtgrp(struct rdt_resource *r,
                                    struct rdt_domain *d);
-void mon_event_read(struct rmid_read *rr, struct rdt_domain *d,
-                   struct rdtgroup *rdtgrp, int evtid, int first);
+void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
+                   struct rdt_domain *d, struct rdtgroup *rdtgrp,
+                   int evtid, int first);
 void mbm_setup_overflow_handler(struct rdt_domain *dom,
                                unsigned long delay_ms);
 void mbm_handle_overflow(struct work_struct *work);

diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 773124b..df964c0 100644 (file)
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -214,9 +214,9 @@ void free_rmid(u32 rmid)
                list_add_tail(&entry->list, &rmid_free_lru);
 }
 
-static u64 mbm_overflow_count(u64 prev_msr, u64 cur_msr)
+static u64 mbm_overflow_count(u64 prev_msr, u64 cur_msr, unsigned int width)
 {
-       u64 shift = 64 - MBM_CNTR_WIDTH, chunks;
+       u64 shift = 64 - width, chunks;
 
        chunks = (cur_msr << shift) - (prev_msr << shift);
        return chunks >>= shift;
@@ -256,7 +256,7 @@ static int __mon_event_count(u32 rmid, struct rmid_read *rr)
                return 0;
        }
 
-       chunks = mbm_overflow_count(m->prev_msr, tval);
+       chunks = mbm_overflow_count(m->prev_msr, tval, rr->r->mbm_width);
        m->chunks += chunks;
        m->prev_msr = tval;
 
@@ -278,7 +278,7 @@ static void mbm_bw_count(u32 rmid, struct rmid_read *rr)
        if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL))
                return;
 
-       chunks = mbm_overflow_count(m->prev_bw_msr, tval);
+       chunks = mbm_overflow_count(m->prev_bw_msr, tval, rr->r->mbm_width);
        m->chunks_bw += chunks;
        m->chunks = m->chunks_bw;
        cur_bw = (chunks * r->mon_scale) >> 20;
@@ -433,11 +433,12 @@ static void update_mba_bw(struct rdtgroup *rgrp, struct rdt_domain *dom_mbm)
        }
 }
 
-static void mbm_update(struct rdt_domain *d, int rmid)
+static void mbm_update(struct rdt_resource *r, struct rdt_domain *d, int rmid)
 {
        struct rmid_read rr;
 
        rr.first = false;
+       rr.r = r;
        rr.d = d;
 
        /*
@@ -510,6 +511,7 @@ void mbm_handle_overflow(struct work_struct *work)
        struct rdtgroup *prgrp, *crgrp;
        int cpu = smp_processor_id();
        struct list_head *head;
+       struct rdt_resource *r;
        struct rdt_domain *d;
 
        mutex_lock(&rdtgroup_mutex);
@@ -517,16 +519,18 @@ void mbm_handle_overflow(struct work_struct *work)
        if (!static_branch_likely(&rdt_mon_enable_key))
                goto out_unlock;
 
-       d = get_domain_from_cpu(cpu, &rdt_resources_all[RDT_RESOURCE_L3]);
+       r = &rdt_resources_all[RDT_RESOURCE_L3];
+
+       d = get_domain_from_cpu(cpu, r);
        if (!d)
                goto out_unlock;
 
        list_for_each_entry(prgrp, &rdt_all_groups, rdtgroup_list) {
-               mbm_update(d, prgrp->mon.rmid);
+               mbm_update(r, d, prgrp->mon.rmid);
 
                head = &prgrp->mon.crdtgrp_list;
                list_for_each_entry(crgrp, head, mon.crdtgrp_list)
-                       mbm_update(d, crgrp->mon.rmid);
+                       mbm_update(r, d, crgrp->mon.rmid);
 
                if (is_mba_sc(NULL))
                        update_mba_bw(prgrp, d);
@@ -619,6 +623,7 @@ int rdt_get_mon_l3_config(struct rdt_resource *r)
 
        r->mon_scale = boot_cpu_data.x86_cache_occ_scale;
        r->num_rmid = boot_cpu_data.x86_cache_max_rmid + 1;
+       r->mbm_width = MBM_CNTR_WIDTH;
 
        /*
         * A reasonable upper limit on the max threshold is the number

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 6276ae0..d7cb5ab 100644 (file)
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -2472,7 +2472,7 @@ static int mkdir_mondata_subdir(struct kernfs_node *parent_kn,
                        goto out_destroy;
 
                if (is_mbm_event(mevt->evtid))
-                       mon_event_read(&rr, d, prgrp, mevt->evtid, true);
+                       mon_event_read(&rr, r, d, prgrp, mevt->evtid, true);
        }
        kernfs_activate(kn);
        return 0;