[PATCH v9 2/9] fs/resctrl: Add resctrl_arch_rmid_idx_match() helper

[Jinjie Ruan]

The current RMID allocator assumes that RMID and CLOSID are entirely
independent or follow a rigid 2D encoding. This prevents architectures
where an RMID is bound to a specific CLOSID from properly filtering
free RMIDs.

Introduce resctrl_arch_rmid_idx_match() to allow architectures to define
their own compatibility rules between a target CLOSID and an allocated
RMID's CLOSID.

No functional change.

Cc: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Cc: Dave Martin <Dave.Martin@xxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Cc: Babu Moger <babu.moger@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Ben Horgan <ben.horgan@xxxxxxx>
Cc: Fenghua Yu <fenghuay@xxxxxxxxxx>
Suggested-by: James Morse <james.morse@xxxxxxx>
Signed-off-by: Zeng Heng <zengheng4@xxxxxxxxxx>
Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
---
 arch/x86/include/asm/resctrl.h |  6 ++++++
 drivers/resctrl/mpam_resctrl.c |  6 ++++++
 fs/resctrl/monitor.c           | 13 +++----------
 include/linux/arm_mpam.h       |  1 +
 4 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
index 8f6edcdcfd87..7bb297a0ab6e 100644
--- a/arch/x86/include/asm/resctrl.h
+++ b/arch/x86/include/asm/resctrl.h
@@ -181,6 +181,12 @@ static inline u32 resctrl_arch_rmid_idx_encode(u32 ignored, u32 rmid)
 	return rmid;
 }
 
+/* x86 RMIDs are independent; any RMID can be used with any CLOSID. */
+static inline bool resctrl_arch_rmid_idx_match(u32 closid, u32 rmid_closid)
+{
+	return true;
+}
+
 /* x86 can always read an rmid, nothing needs allocating */
 struct rdt_resource;
 static inline void *resctrl_arch_mon_ctx_alloc(struct rdt_resource *r,
diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 9d223057953a..385c745787f2 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -279,6 +279,12 @@ u32 resctrl_arch_rmid_idx_encode(u32 closid, u32 rmid)
 	return closid * (mpam_pmg_max + 1) + rmid;
 }
 
+/* Check if the RMID's associated closid matches the target CLOSID. */
+bool resctrl_arch_rmid_idx_match(u32 closid, u32 rmid_closid)
+{
+	return closid == rmid_closid;
+}
+
 void resctrl_arch_rmid_idx_decode(u32 idx, u32 *closid, u32 *rmid)
 {
 	*closid = idx / (mpam_pmg_max + 1);
diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
index 73413cb128ea..39908f67dea4 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -205,23 +205,16 @@ bool has_busy_rmid(struct rdt_l3_mon_domain *d)
 static struct rmid_entry *resctrl_find_free_rmid(u32 closid)
 {
 	struct rmid_entry *itr;
-	u32 itr_idx, cmp_idx;
 
 	if (list_empty(&rmid_free_lru))
 		return rmid_limbo_count ? ERR_PTR(-EBUSY) : ERR_PTR(-ENOSPC);
 
 	list_for_each_entry(itr, &rmid_free_lru, list) {
 		/*
-		 * Get the index of this free RMID, and the index it would need
-		 * to be if it were used with this CLOSID.
-		 * If the CLOSID is irrelevant on this architecture, the two
-		 * index values are always the same on every entry and thus the
-		 * very first entry will be returned.
+		 * Check if the free RMID matches the target CLOSID.
+		 * Architecture-specific rules apply.
 		 */
-		itr_idx = resctrl_arch_rmid_idx_encode(itr->closid, itr->rmid);
-		cmp_idx = resctrl_arch_rmid_idx_encode(closid, itr->rmid);
-
-		if (itr_idx == cmp_idx)
+		if (resctrl_arch_rmid_idx_match(closid, itr->closid))
 			return itr;
 	}
 
diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
index f92a36187a52..0bc8049a3733 100644
--- a/include/linux/arm_mpam.h
+++ b/include/linux/arm_mpam.h
@@ -60,6 +60,7 @@ 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);
+bool resctrl_arch_rmid_idx_match(u32 closid, u32 rmid_closid);
 void resctrl_arch_rmid_idx_decode(u32 idx, u32 *closid, u32 *rmid);
 u32 resctrl_arch_system_num_rmid_idx(void);
 
-- 
2.34.1