[PATCH v11 13/23] x86/resctrl: Handle systems when AET is the only resource

[Tony Luck]

On a system with no L3 monitor resources it should still be possible to
run with just AET.

Update get_rdt_mon_resources() to return true based on whether the
system supports monitoring rather than on the presence of any of the
L3 monitor features.

Make rdt_get_tree() handle the case where AET is the only feature, but
is not enabled for a specific mount.

Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
---
v11:
	Split the AET RMID cap change into separate commit.
	s/Fix get_rdt_mon_resources/Update get_rdt_mon_resources/
	New subject for this patch

 arch/x86/kernel/cpu/resctrl/internal.h | 2 +-
 arch/x86/kernel/cpu/resctrl/core.c     | 7 ++++---
 arch/x86/kernel/cpu/resctrl/monitor.c  | 4 +---
 fs/resctrl/rdtgroup.c                  | 8 ++++++--
 4 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index e46eb9a4c725..d70c8cb1cb81 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -226,7 +226,7 @@ union l3_qos_abmc_cfg {
 
 void rdt_ctrl_update(void *arg);
 
-int rdt_get_l3_mon_config(struct rdt_resource *r);
+void rdt_get_l3_mon_config(struct rdt_resource *r);
 
 bool rdt_cpu_has(int flag);
 
diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index ef37fbb586d3..0ddec2b67e3d 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -1016,10 +1016,11 @@ static __init bool get_rdt_mon_resources(void)
 			ret = true;
 	}
 
-	if (!ret)
-		return false;
+	if (ret)
+		rdt_get_l3_mon_config(r);
 
-	return !rdt_get_l3_mon_config(r);
+	/* Even if there are no L3 monitor events, AET might be supported */
+	return resctrl_arch_system_max_rmid_idx() > 0;
 }
 
 static __init void __check_quirks_intel(void)
diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index bc2df287ccfa..e3485dc55923 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -431,7 +431,7 @@ static void __init intel_rdt_mbm_apply_quirk(u32 num_rmid)
 	mbm_cf = mbm_cf_table[cf_index].cf;
 }
 
-int __init rdt_get_l3_mon_config(struct rdt_resource *r)
+void __init rdt_get_l3_mon_config(struct rdt_resource *r)
 {
 	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
 	unsigned int mbm_offset;
@@ -514,8 +514,6 @@ int __init rdt_get_l3_mon_config(struct rdt_resource *r)
 		intel_rdt_mbm_apply_quirk(r->mon.num_rmid);
 
 	r->mon_capable = true;
-
-	return 0;
 }
 
 static void resctrl_abmc_set_one_amd(void *arg)
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index de07ccdffdb2..3ac518ed2368 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -3195,6 +3195,11 @@ static int rdt_get_tree(struct fs_context *fc)
 		goto out;
 	}
 
+	if (!resctrl_alloc_capable() && !resctrl_mon_capable()) {
+		ret = -EINVAL;
+		goto out;
+	}
+
 	ret = setup_rmid_lru_list();
 	if (ret)
 		goto out;
@@ -3253,8 +3258,7 @@ static int rdt_get_tree(struct fs_context *fc)
 	if (resctrl_mon_capable())
 		resctrl_arch_enable_mon();
 
-	if (resctrl_alloc_capable() || resctrl_mon_capable())
-		resctrl_mounted = true;
+	resctrl_mounted = true;
 
 	if (resctrl_is_mbm_enabled()) {
 		r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
-- 
2.55.0