The default input measurement to the mba_sc feedback loop for
memory bandwidth control when the user mounts with the "mba_MBps"
option is the local bandwidth event.

But some systems may not support a local bandwidth event.

When local bandwidth event is not supported, check for support
of total bandwidth and use that instead.

Relax the mount option check to allow use of the "mba_MBps"
option for systems when only total bandwidth monitoring is
supported. Also update the error message.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
---
 arch/x86/kernel/cpu/resctrl/core.c     | 2 ++
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 4 ++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 94bf559966d6..3d1735ed8d1f 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -965,6 +965,8 @@ static __init bool get_rdt_mon_resources(void)
 
 	if (is_mbm_local_enabled())
 		mba_mbps_default_event = QOS_L3_MBM_LOCAL_EVENT_ID;
+	else if (is_mbm_total_enabled())
+		mba_mbps_default_event = QOS_L3_MBM_TOTAL_EVENT_ID;
 
 	return !rdt_get_mon_l3_config(r);
 }
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 8a52b25ce26b..0659b8e2a71b 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -2341,7 +2341,7 @@ static bool supports_mba_mbps(void)
 	struct rdt_resource *rmbm = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
 	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
 
-	return (is_mbm_local_enabled() &&
+	return (is_mbm_enabled() &&
 		r->alloc_capable && is_mba_linear() &&
 		r->ctrl_scope == rmbm->mon_scope);
 }
@@ -2768,7 +2768,7 @@ static int rdt_parse_param(struct fs_context *fc, struct fs_parameter *param)
 		ctx->enable_cdpl2 = true;
 		return 0;
 	case Opt_mba_mbps:
-		msg = "mba_MBps requires local MBM and linear scale MBA at L3 scope";
+		msg = "mba_MBps requires MBM and linear scale MBA at L3 scope";
 		if (!supports_mba_mbps())
 			return invalfc(fc, msg);
 		ctx->enable_mba_mbps = true;
-- 
2.47.0

The following commit has been merged into the x86/cache branch of tip:

Commit-ID:     141cb5c482b38d7e494a207f881d0fe61e4848ef
Gitweb:        https://git.kernel.org/tip/141cb5c482b38d7e494a207f881d0fe61e4848ef
Author:        Tony Luck <tony.luck@intel.com>
AuthorDate:    Fri, 06 Dec 2024 08:31:45 -08:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Tue, 10 Dec 2024 16:15:14 +01:00

x86/resctrl: Make mba_sc use total bandwidth if local is not supported

The default input measurement to the mba_sc feedback loop for memory bandwidth
control when the user mounts with the "mba_MBps" option is the local bandwidth
event. But some systems may not support a local bandwidth event.

When local bandwidth event is not supported, check for support of total
bandwidth and use that instead.

Relax the mount option check to allow use of the "mba_MBps" option for systems
when only total bandwidth monitoring is supported. Also update the error
message.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Link: https://lore.kernel.org/r/20241206163148.83828-6-tony.luck@intel.com
---
 arch/x86/kernel/cpu/resctrl/core.c     | 2 ++
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 4 ++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 94bf559..3d1735e 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -965,6 +965,8 @@ static __init bool get_rdt_mon_resources(void)
 
 	if (is_mbm_local_enabled())
 		mba_mbps_default_event = QOS_L3_MBM_LOCAL_EVENT_ID;
+	else if (is_mbm_total_enabled())
+		mba_mbps_default_event = QOS_L3_MBM_TOTAL_EVENT_ID;
 
 	return !rdt_get_mon_l3_config(r);
 }
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 8a52b25..0659b8e 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -2341,7 +2341,7 @@ static bool supports_mba_mbps(void)
 	struct rdt_resource *rmbm = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
 	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
 
-	return (is_mbm_local_enabled() &&
+	return (is_mbm_enabled() &&
 		r->alloc_capable && is_mba_linear() &&
 		r->ctrl_scope == rmbm->mon_scope);
 }
@@ -2768,7 +2768,7 @@ static int rdt_parse_param(struct fs_context *fc, struct fs_parameter *param)
 		ctx->enable_cdpl2 = true;
 		return 0;
 	case Opt_mba_mbps:
-		msg = "mba_MBps requires local MBM and linear scale MBA at L3 scope";
+		msg = "mba_MBps requires MBM and linear scale MBA at L3 scope";
 		if (!supports_mba_mbps())
 			return invalfc(fc, msg);
 		ctx->enable_mba_mbps = true;