From: Babu Moger <babu.moger@amd.com>
Date: Fri, 5 Sep 2025 21:34:31 +0000 (-0500)
Subject: x86/resctrl: Configure mbm_event mode if supported
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=0f1576e43adc62756879a240e66e89ce386b6eb9;p=thirdparty%2Fkernel%2Fstable.git

x86/resctrl: Configure mbm_event mode if supported

Configure mbm_event mode on AMD platforms. On AMD platforms, it is
recommended to use the mbm_event mode, if supported, to prevent the
hardware from resetting counters between reads. This can result in
misleading values or display "Unavailable" if no counter is assigned
to the event.

Enable mbm_event mode, known as ABMC (Assignable Bandwidth Monitoring
Counters) on AMD, by default if the system supports it.

Update ABMC across all logical processors within the resctrl domain to
ensure proper functionality.

Signed-off-by: Babu Moger <babu.moger@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com
---

diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 2e68aa02ad3f4..06ca5a30140c2 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -520,6 +520,9 @@ static void domain_add_cpu_mon(int cpu, struct rdt_resource *r)
 		d = container_of(hdr, struct rdt_mon_domain, hdr);
 
 		cpumask_set_cpu(cpu, &d->hdr.cpu_mask);
+		/* Update the mbm_assign_mode state for the CPU if supported */
+		if (r->mon.mbm_cntr_assignable)
+			resctrl_arch_mbm_cntr_assign_set_one(r);
 		return;
 	}
 
@@ -539,6 +542,10 @@ static void domain_add_cpu_mon(int cpu, struct rdt_resource *r)
 	d->ci_id = ci->id;
 	cpumask_set_cpu(cpu, &d->hdr.cpu_mask);
 
+	/* Update the mbm_assign_mode state for the CPU if supported */
+	if (r->mon.mbm_cntr_assignable)
+		resctrl_arch_mbm_cntr_assign_set_one(r);
+
 	arch_mon_domain_online(r, d);
 
 	if (arch_domain_mbm_alloc(r->mon.num_rmid, hw_dom)) {
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index e5edddb290c9d..9f4c2f0aaf5c8 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -215,5 +215,6 @@ bool rdt_cpu_has(int flag);
 void __init intel_rdt_mbm_apply_quirk(void);
 
 void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
+void resctrl_arch_mbm_cntr_assign_set_one(struct rdt_resource *r);
 
 #endif /* _ASM_X86_RESCTRL_INTERNAL_H */
diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 0b3c199e9e016..c8945610d4555 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -456,6 +456,7 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
 		r->mon.mbm_cntr_assignable = true;
 		cpuid_count(0x80000020, 5, &eax, &ebx, &ecx, &edx);
 		r->mon.num_mbm_cntrs = (ebx & GENMASK(15, 0)) + 1;
+		hw_res->mbm_cntr_assign_enabled = true;
 	}
 
 	r->mon_capable = true;
@@ -557,3 +558,10 @@ void resctrl_arch_config_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
 	if (am)
 		memset(am, 0, sizeof(*am));
 }
+
+void resctrl_arch_mbm_cntr_assign_set_one(struct rdt_resource *r)
+{
+	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
+
+	resctrl_abmc_set_one_amd(&hw_res->mbm_cntr_assign_enabled);
+}