linux-kernel - [PATCH v3 24/47] arm_mpam: resctrl: Add rmid index helpers

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Message-ID: <20260112165914.4086692-25-ben.horgan@arm.com>
Date: Mon, 12 Jan 2026 16:58:51 +0000
From: Ben Horgan <ben.horgan@....com>
To: ben.horgan@....com
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Subject: [PATCH v3 24/47] arm_mpam: resctrl: Add rmid index helpers

Because MPAM's pmg aren't identical to RDT's rmid, resctrl handles some
data structures by index. This allows x86 to map indexes to RMID, and MPAM
to map them to partid-and-pmg.

Add the helpers to do this.

Suggested-by: James Morse <james.morse@....com>
Signed-off-by: Ben Horgan <ben.horgan@....com>
---
Changes since rfc:
Use ~0U instead of ~0 in lhs of left shift

Changes since v2:
Drop changes signed-off-by as reworked patch
Use multiply and add rather than shift to avoid holes
---
 drivers/resctrl/mpam_resctrl.c | 16 ++++++++++++++++
 include/linux/arm_mpam.h       |  3 +++
 2 files changed, 19 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index b6bbe73bc248..92b2a2d4b51d 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -126,6 +126,22 @@ u32 resctrl_arch_get_num_closid(struct rdt_resource *ignored)
 	return mpam_partid_max + 1;
 }
 
+u32 resctrl_arch_system_num_rmid_idx(void)
+{
+	return (mpam_pmg_max + 1) * (mpam_partid_max + 1);
+}
+
+u32 resctrl_arch_rmid_idx_encode(u32 closid, u32 rmid)
+{
+	return closid * (mpam_pmg_max + 1) + rmid;
+}
+
+void resctrl_arch_rmid_idx_decode(u32 idx, u32 *closid, u32 *rmid)
+{
+	*closid = idx / (mpam_pmg_max + 1);
+	*rmid = idx % (mpam_pmg_max + 1);
+}
+
 void resctrl_arch_sched_in(struct task_struct *tsk)
 {
 	lockdep_assert_preemption_disabled();
diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
index d329b1dc148b..7d23c90f077d 100644
--- a/include/linux/arm_mpam.h
+++ b/include/linux/arm_mpam.h
@@ -58,6 +58,9 @@ void resctrl_arch_set_cpu_default_closid_rmid(int cpu, u32 closid, u32 rmid);
 void resctrl_arch_sched_in(struct task_struct *tsk);
 bool resctrl_arch_match_closid(struct task_struct *tsk, u32 closid);
 bool resctrl_arch_match_rmid(struct task_struct *tsk, u32 closid, u32 rmid);
+u32 resctrl_arch_rmid_idx_encode(u32 closid, u32 rmid);
+void resctrl_arch_rmid_idx_decode(u32 idx, u32 *closid, u32 *rmid);
+u32 resctrl_arch_system_num_rmid_idx(void);
 
 /**
  * mpam_register_requestor() - Register a requestor with the MPAM driver
-- 
2.43.0