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x86/resctrl: Maintain MBM counter width per resource

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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
This commit is contained in:
Reinette Chatre
2020-05-05 15:36:16 -07:00
committed by Borislav Petkov
parent 923f3a2b48
commit 46637d4570
4 changed files with 24 additions and 14 deletions
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8
arch/x86/kernel/cpu/resctrl/ctrlmondata.c
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@@ -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");