Hi Shaopeng,

On 1/8/26 10:36, Shaopeng Tan (Fujitsu) wrote:

Hello Ben,

quoted

From: James Morse <james.morse@arm.com>

resctrl has its own data structures to describe its resources. We can't use
these directly as we play tricks with the 'MBA' resource, picking the MPAM
controls or monitors that best apply. We may export the same component as
both L3 and MBA.

Add mpam_resctrl_exports[] as the array of class->resctrl mappings we are
exporting, and add the cpuhp hooks that allocated and free the resctrl
domain structures.

While we're here, plumb in a few other obvious things.

CONFIG_ARM_CPU_RESCTRL is used to allow this code to be built even though
it can't yet be linked against resctrl.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
Domain list is an rcu list
Add synchronize_rcu() to free the deleted element
Code flow simplification (Jonathan)
---

[...]

quoted

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 860181266b15..303aacfcb9d6 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c

@@ -1628,6 +1628,9 @@ static int mpam_cpu_online(unsigned int cpu)
                         mpam_reprogram_msc(msc);
         }
 
+       if (mpam_is_enabled())
+               mpam_resctrl_online_cpu(cpu);

return mpam_resctrl_online_cpu(cpu);

Ack

Considering the fixes added in [PATCH v2 27/45],
How about changing the code as follows? 

+		err = mpam_resctrl_control_init(res, i);
+		if (err) {
+			pr_debug("Failed to initialise rid %u\n", i);
+			pr_debug("Internal error %d - resctrl not supported\n", err);
+			cpus_read_unlock();
+			return err;
+		}
+	}
+           /* Find some classes to use for monitors */
+         mpam_resctrl_pick_counters();
+         for (enum resctrl_event_id j = 0; j < QOS_NUM_EVENTS; j++) {
+         …
+ }
+	cpus_read_unlock();

Hmm, probably better to propagate the error from
mpam_resctrl_monitor_init_abmc() rather moving the early exit.

Best regards,
Shaopeng TAN

quoted

+       if (!exposed_alloc_capable && !exposed_mon_capable) {
+               pr_debug("No alloc(%u) or monitor(%u) found - resctrl not supported\n",
+                        exposed_alloc_capable, exposed_mon_capable);
+               return -EOPNOTSUPP;
+       }
+
+       if (!is_power_of_2(mpam_pmg_max + 1)) {
+               /*
+                * If not all the partid*pmg values are valid indexes,
+                * resctrl may allocate pmg that don't exist. This
+                * should cause an error interrupt.
+                */
+               pr_warn("Number of PMG is not a power of 2! resctrl may misbehave");
+       }
+
+       /* TODO: call resctrl_init() */
+
+       return err;
+}

diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
index 7f00c5285a32..2c7d1413a401 100644
--- a/include/linux/arm_mpam.h
+++ b/include/linux/arm_mpam.h

@@ -49,6 +49,9 @@ static inline int mpam_ris_create(struct mpam_msc *msc, u8 ris_idx,
 }
 #endif
 
+bool resctrl_arch_alloc_capable(void);
+bool resctrl_arch_mon_capable(void);
+
 /**
  * mpam_register_requestor() - Register a requestor with the MPAM driver
  * @partid_max:                The maximum PARTID value the requestor can generate.
--

2.43.0

Thanks,

Ben