[PATCH v11 02/23] x86/resctrl: Check if monitoring features are enabled

[Tony Luck]

Both Intel and AMD manuals say that software must first check
CPUID(0x7,0x0).EBX[12] to see if any monitoring features are enabled
before checking for specific features enabled in subleaves.

Each of the L3-based monitoring features is gated by X86_FEATURE_L3_MON

Add check feature bits.

Fixes: cbc82b172638 ("x86: Add support for Intel Cache QoS Monitoring (CQM) detection")
Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
---
v11:
	New patch

 arch/x86/kernel/cpu/resctrl/core.c | 33 ++++++++++++++++++------------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 2435eddd24eb..fcbecf677914 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -968,20 +968,27 @@ static __init bool get_rdt_mon_resources(void)
 	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
 	bool ret = false;
 
-	if (rdt_cpu_has(X86_FEATURE_CQM_OCCUP_LLC)) {
-		resctrl_enable_mon_event(QOS_L3_OCCUP_EVENT_ID, false, 0, NULL);
-		ret = true;
-	}
-	if (rdt_cpu_has(X86_FEATURE_CQM_MBM_TOTAL)) {
-		resctrl_enable_mon_event(QOS_L3_MBM_TOTAL_EVENT_ID, false, 0, NULL);
-		ret = true;
-	}
-	if (rdt_cpu_has(X86_FEATURE_CQM_MBM_LOCAL)) {
-		resctrl_enable_mon_event(QOS_L3_MBM_LOCAL_EVENT_ID, false, 0, NULL);
-		ret = true;
+	/* Any monitoring at all? */
+	if (!cpu_feature_enabled(X86_FEATURE_RDT_M))
+		return false;
+
+	/* Any of the L3 monitoring features? */
+	if (cpu_feature_enabled(X86_FEATURE_L3_MON)) {
+		if (rdt_cpu_has(X86_FEATURE_CQM_OCCUP_LLC)) {
+			resctrl_enable_mon_event(QOS_L3_OCCUP_EVENT_ID, false, 0, NULL);
+			ret = true;
+		}
+		if (rdt_cpu_has(X86_FEATURE_CQM_MBM_TOTAL)) {
+			resctrl_enable_mon_event(QOS_L3_MBM_TOTAL_EVENT_ID, false, 0, NULL);
+			ret = true;
+		}
+		if (rdt_cpu_has(X86_FEATURE_CQM_MBM_LOCAL)) {
+			resctrl_enable_mon_event(QOS_L3_MBM_LOCAL_EVENT_ID, false, 0, NULL);
+			ret = true;
+		}
+		if (rdt_cpu_has(X86_FEATURE_ABMC))
+			ret = true;
 	}
-	if (rdt_cpu_has(X86_FEATURE_ABMC))
-		ret = true;
 
 	if (!ret)
 		return false;
-- 
2.55.0