[RFC PATCH v2 09/10] arm_mpam: resctrl: Require monitoring components to cover the same CPUs

[Reinette Chatre]

A monitoring domain records the component that backs each of its
monitoring events and takes its ID from one of these components. The
domain represents the CPUs of one L3 cache, while each event's counters
are read from the event's own component.

If the components of a monitoring domain covered different CPUs, the
counts of an event would not belong to the CPUs that the domain
represents. This is not expected to happen: every class picked for
monitoring covers all CPUs and has components that correspond to the
L3 caches.

Fail setting up the monitoring domain, with a warning, if the components
backing its events do not all cover the same CPUs. Compare each
component with the one found before it, instead of naming the events,
so that the check applies to any monitoring event.

Signed-off-by: Reinette Chatre <reinette.chatre at intel.com>
---
 drivers/resctrl/mpam_resctrl.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 36a924734484..c3ea61a40bb2 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -1664,6 +1664,12 @@ static int mpam_resctrl_setup_mon_domain(unsigned int cpu,
 		if (WARN_ON_ONCE(!mon_comp))
 			return -EFAULT;
 
+		/* All components of a monitoring domain cover the same CPUs */
+		if (WARN_ON_ONCE(any_mon_comp &&
+				 !cpumask_equal(&any_mon_comp->affinity,
+						&mon_comp->affinity)))
+			return -EFAULT;
+
 		dom->mon_comp[eventid] = mon_comp;
 		any_mon_comp = mon_comp;
 	}
-- 
2.55.0