[PATCH v2 1/1] arm_mpam: Introduce resctrl_arch_mbm_has_long_counter()

[Shanker Donthineni]

It takes a substantial amount of time for long counters, which have more
than 32 bits, to cause overflow. To support enable/disable of a periodic
handler for monitoring memory bandwidth, introduce a common function
resctrl_arch_mbm_has_long_counter(). FOr MPAM, disable periodic handler
if the MSC component is capable of supporting 63-bit counters.

Signed-off-by: Shanker Donthineni <sdonthineni at nvidia.com>
---
Changes since v1:
 - Skip 32bit overflow of MBW when checking config mismatch

 arch/x86/include/asm/resctrl.h       |  5 +++++
 drivers/platform/mpam/mpam_devices.c |  2 ++
 drivers/platform/mpam/mpam_resctrl.c | 11 +++++++++++
 fs/resctrl/rdtgroup.c                |  9 +++++----
 include/linux/arm_mpam.h             |  1 +
 5 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
index 1adf16660ac10..96c7d86ab9b69 100644
--- a/arch/x86/include/asm/resctrl.h
+++ b/arch/x86/include/asm/resctrl.h
@@ -100,6 +100,11 @@ static inline bool resctrl_arch_is_mbm_local_enabled(void)
 	return (rdt_mon_features & (1 << QOS_L3_MBM_LOCAL_EVENT_ID));
 }
 
+static bool resctrl_arch_mbm_has_long_counter(void)
+{
+	return false;
+}
+
 /*
  * __resctrl_sched_in() - Writes the task's CLOSid/RMID to IA32_PQR_MSR
  *
diff --git a/drivers/platform/mpam/mpam_devices.c b/drivers/platform/mpam/mpam_devices.c
index f7bcf9737dcf8..5d90eaa66711d 100644
--- a/drivers/platform/mpam/mpam_devices.c
+++ b/drivers/platform/mpam/mpam_devices.c
@@ -870,6 +870,8 @@ static void read_msmon_ctl_flt_vals(struct mon_read *m, u32 *ctl_val,
 	case mpam_feat_msmon_mbwu:
 		*ctl_val = mpam_read_monsel_reg(msc, CFG_MBWU_CTL);
 		*flt_val = mpam_read_monsel_reg(msc, CFG_MBWU_FLT);
+		if (mpam_ris_has_mbwu_long_counter(m->ris))
+			*ctl_val &= ~MSMON_CFG_x_CTL_OFLOW_STATUS;
 		break;
 	default:
 		return;
diff --git a/drivers/platform/mpam/mpam_resctrl.c b/drivers/platform/mpam/mpam_resctrl.c
index 8ec963aca9d49..dee82b3c0dbe3 100644
--- a/drivers/platform/mpam/mpam_resctrl.c
+++ b/drivers/platform/mpam/mpam_resctrl.c
@@ -81,6 +81,17 @@ bool resctrl_arch_is_mbm_total_enabled(void)
 	return mbm_total_class;
 }
 
+bool resctrl_arch_mbm_has_long_counter(void)
+{
+	if (mbm_local_class)
+		return !!mpam_has_feature(mpam_feat_msmon_mbwu_63counter, &mbm_local_class->props);
+
+	if (mbm_total_class)
+		return !!mpam_has_feature(mpam_feat_msmon_mbwu_63counter, &mbm_total_class->props);
+
+	return false;
+}
+
 bool resctrl_arch_get_cdp_enabled(enum resctrl_res_level rid)
 {
 	switch (rid) {
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 43efed317f1b7..cff77915395b0 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -2774,7 +2774,7 @@ static int rdt_get_tree(struct fs_context *fc)
 	if (resctrl_arch_alloc_capable() || resctrl_arch_mon_capable())
 		resctrl_mounted = true;
 
-	if (resctrl_is_mbm_enabled()) {
+	if (resctrl_is_mbm_enabled() && (!resctrl_arch_mbm_has_long_counter())) {
 		list_for_each_entry(dom, &l3->domains, list)
 			mbm_setup_overflow_handler(dom, MBM_OVERFLOW_INTERVAL,
 						   RESCTRL_PICK_ANY_CPU);
@@ -4014,7 +4014,7 @@ static void _resctrl_offline_domain(struct rdt_resource *r,
 	if (resctrl_mounted && resctrl_arch_mon_capable())
 		rmdir_mondata_subdir_allrdtgrp(r, d->id);
 
-	if (resctrl_is_mbm_enabled())
+	if (resctrl_is_mbm_enabled() && (!resctrl_arch_mbm_has_long_counter()))
 		cancel_delayed_work(&d->mbm_over);
 	if (resctrl_arch_is_llc_occupancy_enabled() && has_busy_rmid(d)) {
 		/*
@@ -4087,7 +4087,7 @@ static int _resctrl_online_domain(struct rdt_resource *r, struct rdt_domain *d)
 	if (err)
 		return err;
 
-	if (resctrl_is_mbm_enabled()) {
+	if (resctrl_is_mbm_enabled() && (!resctrl_arch_mbm_has_long_counter())) {
 		INIT_DELAYED_WORK(&d->mbm_over, mbm_handle_overflow);
 		mbm_setup_overflow_handler(d, MBM_OVERFLOW_INTERVAL,
 					   RESCTRL_PICK_ANY_CPU);
@@ -4155,7 +4155,8 @@ void resctrl_offline_cpu(unsigned int cpu)
 
 	d = resctrl_get_domain_from_cpu(cpu, l3);
 	if (d) {
-		if (resctrl_is_mbm_enabled() && cpu == d->mbm_work_cpu) {
+		if (resctrl_is_mbm_enabled() && (!resctrl_arch_mbm_has_long_counter()) &&
+			cpu == d->mbm_work_cpu) {
 			cancel_delayed_work(&d->mbm_over);
 			mbm_setup_overflow_handler(d, 0, cpu);
 		}
diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
index 8b80745132723..766117c5ff555 100644
--- a/include/linux/arm_mpam.h
+++ b/include/linux/arm_mpam.h
@@ -79,6 +79,7 @@ bool resctrl_arch_mon_capable(void);
 bool resctrl_arch_is_llc_occupancy_enabled(void);
 bool resctrl_arch_is_mbm_local_enabled(void);
 bool resctrl_arch_is_mbm_total_enabled(void);
+bool resctrl_arch_mbm_has_long_counter(void);
 
 /* reset cached configurations, then all devices */
 void resctrl_arch_reset_resources(void);
-- 
2.25.1