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Message-Id: <20251017185645.26604-28-james.morse@arm.com>
Date: Fri, 17 Oct 2025 18:56:43 +0000
From: James Morse <james.morse@....com>
To: linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
linux-acpi@...r.kernel.org
Cc: James Morse <james.morse@....com>,
D Scott Phillips OS <scott@...amperecomputing.com>,
carl@...amperecomputing.com,
lcherian@...vell.com,
bobo.shaobowang@...wei.com,
tan.shaopeng@...itsu.com,
baolin.wang@...ux.alibaba.com,
Jamie Iles <quic_jiles@...cinc.com>,
Xin Hao <xhao@...ux.alibaba.com>,
peternewman@...gle.com,
dfustini@...libre.com,
amitsinght@...vell.com,
David Hildenbrand <david@...hat.com>,
Dave Martin <dave.martin@....com>,
Koba Ko <kobak@...dia.com>,
Shanker Donthineni <sdonthineni@...dia.com>,
fenghuay@...dia.com,
baisheng.gao@...soc.com,
Jonathan Cameron <jonathan.cameron@...wei.com>,
Rob Herring <robh@...nel.org>,
Rohit Mathew <rohit.mathew@....com>,
Rafael Wysocki <rafael@...nel.org>,
Len Brown <lenb@...nel.org>,
Lorenzo Pieralisi <lpieralisi@...nel.org>,
Hanjun Guo <guohanjun@...wei.com>,
Sudeep Holla <sudeep.holla@....com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Danilo Krummrich <dakr@...nel.org>,
Jeremy Linton <jeremy.linton@....com>,
Gavin Shan <gshan@...hat.com>,
Fenghua Yu <fenghuay@...ia.com>
Subject: [PATCH v3 27/29] arm_mpam: Add helper to reset saved mbwu state
resctrl expects to reset the bandwidth counters when the filesystem
is mounted.
To allow this, add a helper that clears the saved mbwu state. Instead
of cross calling to each CPU that can access the component MSC to
write to the counter, set a flag that causes it to be zero'd on the
the next read. This is easily done by forcing a configuration update.
Signed-off-by: James Morse <james.morse@....com>
Reviewed-by: Fenghua Yu <fenghuay@...ia.com>
Tested-by: Fenghua Yu <fenghuay@...dia.com>
---
Changes since v2:
* Switched to guard and fixed non _srcu list walker.
* Made a comment about what is proteted by which lock a list.
---
drivers/resctrl/mpam_devices.c | 46 ++++++++++++++++++++++++++++++++-
drivers/resctrl/mpam_internal.h | 7 ++++-
2 files changed, 51 insertions(+), 2 deletions(-)
diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index c207a6d2832c..89d4f42168ed 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -1066,9 +1066,11 @@ static u64 mpam_msmon_overflow_val(enum mpam_device_features type)
static void __ris_msmon_read(void *arg)
{
bool nrdy = false;
+ bool config_mismatch;
struct mon_read *m = arg;
u64 now, overflow_val = 0;
struct mon_cfg *ctx = m->ctx;
+ bool reset_on_next_read = false;
struct mpam_msc_ris *ris = m->ris;
struct msmon_mbwu_state *mbwu_state;
struct mpam_props *rprops = &ris->props;
@@ -1083,6 +1085,14 @@ static void __ris_msmon_read(void *arg)
FIELD_PREP(MSMON_CFG_MON_SEL_RIS, ris->ris_idx);
mpam_write_monsel_reg(msc, CFG_MON_SEL, mon_sel);
+ if (m->type == mpam_feat_msmon_mbwu) {
+ mbwu_state = &ris->mbwu_state[ctx->mon];
+ if (mbwu_state) {
+ reset_on_next_read = mbwu_state->reset_on_next_read;
+ mbwu_state->reset_on_next_read = false;
+ }
+ }
+
/*
* Read the existing configuration to avoid re-writing the same values.
* This saves waiting for 'nrdy' on subsequent reads.
@@ -1090,7 +1100,10 @@ static void __ris_msmon_read(void *arg)
read_msmon_ctl_flt_vals(m, &cur_ctl, &cur_flt);
clean_msmon_ctl_val(&cur_ctl);
gen_msmon_ctl_flt_vals(m, &ctl_val, &flt_val);
- if (cur_flt != flt_val || cur_ctl != (ctl_val | MSMON_CFG_x_CTL_EN))
+ config_mismatch = cur_flt != flt_val ||
+ cur_ctl != (ctl_val | MSMON_CFG_x_CTL_EN);
+
+ if (config_mismatch || reset_on_next_read)
write_msmon_ctl_flt_vals(m, ctl_val, flt_val);
switch (m->type) {
@@ -1242,6 +1255,37 @@ int mpam_msmon_read(struct mpam_component *comp, struct mon_cfg *ctx,
return err;
}
+void mpam_msmon_reset_mbwu(struct mpam_component *comp, struct mon_cfg *ctx)
+{
+ struct mpam_msc *msc;
+ struct mpam_vmsc *vmsc;
+ struct mpam_msc_ris *ris;
+
+ if (!mpam_is_enabled())
+ return;
+
+ guard(srcu)(&mpam_srcu);
+ list_for_each_entry_srcu(vmsc, &comp->vmsc, comp_list,
+ srcu_read_lock_held(&mpam_srcu)) {
+ if (!mpam_has_feature(mpam_feat_msmon_mbwu, &vmsc->props))
+ continue;
+
+ msc = vmsc->msc;
+ list_for_each_entry_srcu(ris, &vmsc->ris, vmsc_list,
+ srcu_read_lock_held(&mpam_srcu)) {
+ if (!mpam_has_feature(mpam_feat_msmon_mbwu, &ris->props))
+ continue;
+
+ if (WARN_ON_ONCE(!mpam_mon_sel_lock(msc)))
+ continue;
+
+ ris->mbwu_state[ctx->mon].correction = 0;
+ ris->mbwu_state[ctx->mon].reset_on_next_read = true;
+ mpam_mon_sel_unlock(msc);
+ }
+ }
+}
+
static void mpam_reset_msc_bitmap(struct mpam_msc *msc, u16 reg, u16 wd)
{
u32 num_words, msb;
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index ff38b4bbfc2b..6632699ae814 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -204,10 +204,14 @@ struct mon_cfg {
/*
* Changes to enabled and cfg are protected by the msc->lock.
- * Changes to prev_val and correction are protected by the msc's mon_sel_lock.
+ * The msc's mon_sel_lock protects:
+ * - reset_on_next_read
+ * - prev_val
+ * - correction
*/
struct msmon_mbwu_state {
bool enabled;
+ bool reset_on_next_read;
struct mon_cfg cfg;
/* The value last read from the hardware. Used to detect overflow. */
@@ -369,6 +373,7 @@ int mpam_apply_config(struct mpam_component *comp, u16 partid,
int mpam_msmon_read(struct mpam_component *comp, struct mon_cfg *ctx,
enum mpam_device_features, u64 *val);
+void mpam_msmon_reset_mbwu(struct mpam_component *comp, struct mon_cfg *ctx);
int mpam_get_cpumask_from_cache_id(unsigned long cache_id, u32 cache_level,
cpumask_t *affinity);
--
2.39.5
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