[PATCH v12 20/25] x86/resctrl: Enforce system RMID limit on AET

[Tony Luck]

AET (Application Energy Telemetry) event groups each support a specific
number of RMIDs. But that number may be lower than the number supported
by the system. This is especially true on systems with SNC (Sub-NUMA Cluster)
enabled as that reduces the number of supported RMIDs.

Reduce r->mon.num_rmid if needed to ensure that info/PERF_PKG_MON/num_rmids
does not display an unachievable value to users.

Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
---
v12:
	Replacement for v11 patch 14 "Enforce system RMID limit ..."
---
 arch/x86/kernel/cpu/resctrl/core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 3bf4d1a07593..a20439a5099a 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -798,6 +798,12 @@ void resctrl_arch_pre_mount(void)
 	if (!intel_aet_pre_mount())
 		return;
 
+	/*
+	 * AET may claim to support more RMIDs than are permitted to be
+	 * assigned to IA32_PQR_ASSOC.RMID. Enforce this limit.
+	 */
+	r->mon.num_rmid = min(r->mon.num_rmid, pqr_assoc_num_rmid);
+
 	/*
 	 * Late discovery of telemetry events means the domains for the
 	 * resource were not built. Do that now.
-- 
2.55.0