linux-kernel - [PATCH] x86/resctrl: Fix arch_mbm

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Message-ID: <20240722204611.3549213-1-peternewman@google.com>
Date: Mon, 22 Jul 2024 13:46:11 -0700
From: Peter Newman <peternewman@...gle.com>
To: Fenghua Yu <fenghua.yu@...el.com>, Reinette Chatre <reinette.chatre@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H . Peter Anvin" <hpa@...or.com>, Shaopeng Tan <tan.shaopeng@...itsu.com>, 
	James Morse <james.morse@....com>, Babu Moger <babu.moger@....com>, 
	Peter Newman <peternewman@...gle.com>, Tony Luck <tony.luck@...el.com>, 
	Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>, linux-kernel@...r.kernel.org, 
	eranian@...gle.com, irogers@...gle.com, namhyung@...gle.com
Subject: [PATCH] x86/resctrl: Fix arch_mbm_* array overrun on SNC

When using resctrl on systems with Sub-NUMA Clustering enabled,
monitoring groups may be allocated RMID values which would overrun the
arch_mbm_{local,total} arrays.

This is due to inconsistencies in whether the SNC-adjusted num_rmid
value or the unadjusted value in resctrl_arch_system_num_rmid_idx() is
used. The num_rmid value for the L3 resource is currently:

 resctrl_arch_system_num_rmid_idx() / snc_nodes_per_l3_cache

As a simple fix, make resctrl_arch_system_num_rmid_idx() return the
SNC-adjusted, L3 num_rmid value on x86.

Fixes: e13db55b5a0d ("x86/resctrl: Introduce snc_nodes_per_l3_cache")
Signed-off-by: Peter Newman <peternewman@...gle.com>
---
 arch/x86/include/asm/resctrl.h     | 6 ------
 arch/x86/kernel/cpu/resctrl/core.c | 8 ++++++++
 include/linux/resctrl.h            | 3 +++
 3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
index 12dbd2588ca7..8b1b6ce1e51b 100644
--- a/arch/x86/include/asm/resctrl.h
+++ b/arch/x86/include/asm/resctrl.h
@@ -156,12 +156,6 @@ static inline void resctrl_sched_in(struct task_struct *tsk)
 		__resctrl_sched_in(tsk);
 }
 
-static inline u32 resctrl_arch_system_num_rmid_idx(void)
-{
-	/* RMID are independent numbers for x86. num_rmid_idx == num_rmid */
-	return boot_cpu_data.x86_cache_max_rmid + 1;
-}
-
 static inline void resctrl_arch_rmid_idx_decode(u32 idx, u32 *closid, u32 *rmid)
 {
 	*rmid = idx;
diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 1930fce9dfe9..8591d53c144b 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -119,6 +119,14 @@ struct rdt_hw_resource rdt_resources_all[] = {
 	},
 };
 
+u32 resctrl_arch_system_num_rmid_idx(void)
+{
+	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
+
+	/* RMID are independent numbers for x86. num_rmid_idx == num_rmid */
+	return r->num_rmid;
+}
+
 /*
  * cache_alloc_hsw_probe() - Have to probe for Intel haswell server CPUs
  * as they do not have CPUID enumeration support for Cache allocation.
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index b0875b99e811..43ac241471b3 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -248,6 +248,9 @@ struct resctrl_schema {
 
 /* The number of closid supported by this resource regardless of CDP */
 u32 resctrl_arch_get_num_closid(struct rdt_resource *r);
+
+u32 resctrl_arch_system_num_rmid_idx(void);
+
 int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid);
 
 /*
-- 
2.45.2.1089.g2a221341d9-goog