Commit 46637d45 authored by Reinette Chatre's avatar Reinette Chatre Committed by Borislav Petkov
Browse files

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: default avatarReinette Chatre <reinette.chatre@intel.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/e36743b9800f16ce600f86b89127391f61261f23.1588715690.git.reinette.chatre@intel.com
parent 923f3a2b

arch/x86/kernel/cpu/resctrl/ctrlmondata.c

+5 −3
Original line number Diff line number Diff line
@@ -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");

arch/x86/kernel/cpu/resctrl/internal.h

+5 −2
Original line number Diff line number Diff line
@@ -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);

arch/x86/kernel/cpu/resctrl/monitor.c

+13 −8
Original line number Diff line number Diff line
@@ -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

arch/x86/kernel/cpu/resctrl/rdtgroup.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

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