linux-kernel - [PATCH v6 23/24] x86/resctrl: Move domain helper migration into resctrl_offline

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Message-Id: <20230914172138.11977-24-james.morse@arm.com>
Date:   Thu, 14 Sep 2023 17:21:37 +0000
From:   James Morse <james.morse@....com>
To:     x86@...nel.org, linux-kernel@...r.kernel.org
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Babu Moger <Babu.Moger@....com>,
        James Morse <james.morse@....com>,
        shameerali.kolothum.thodi@...wei.com,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        carl@...amperecomputing.com, lcherian@...vell.com,
        bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
        xingxin.hx@...nanolis.org, baolin.wang@...ux.alibaba.com,
        Jamie Iles <quic_jiles@...cinc.com>,
        Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
        dfustini@...libre.com, amitsinght@...vell.com
Subject: [PATCH v6 23/24] x86/resctrl: Move domain helper migration into resctrl_offline_cpu()

When a CPU is taken offline the resctrl filesystem code needs to check
if it was the CPU nominated to perform the periodic overflow and limbo
work. If so, another CPU needs to be chosen to do this work.

This is currently done in core.c, mixed in with the code that removes
the CPU from the domain's mask, and potentially free()s the domain.

Move the migration of the overflow and limbo helpers into the filesystem
code, into resctrl_offline_cpu(). As resctrl_offline_cpu() runs before
the architecture code has removed the CPU from the domain mask, the
callers need to be told which CPU is being removed, to avoid picking
it as the new CPU. This uses the exclude_cpu feature previously
added.

Reviewed-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
Tested-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
Tested-By: Peter Newman <peternewman@...gle.com>
Signed-off-by: James Morse <james.morse@....com>
---
Changes since v5:
 * Changed fir tree order of variables.
 * Added mon-capable check for cpu offline.
---
 arch/x86/kernel/cpu/resctrl/core.c     | 16 ----------------
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 18 ++++++++++++++++++
 2 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 00b1592fd059..1a10f567bbe5 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -578,22 +578,6 @@ static void domain_remove_cpu(int cpu, struct rdt_resource *r)
 
 		return;
 	}
-
-	if (r == &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl) {
-		if (is_mbm_enabled() && cpu == d->mbm_work_cpu) {
-			cancel_delayed_work(&d->mbm_over);
-			/*
-			 * temporary: exclude_cpu=-1 as this CPU has already
-			 * been removed by cpumask_clear_cpu()d
-			 */
-			mbm_setup_overflow_handler(d, 0, RESCTRL_PICK_ANY_CPU);
-		}
-		if (is_llc_occupancy_enabled() && cpu == d->cqm_work_cpu &&
-		    has_busy_rmid(d)) {
-			cancel_delayed_work(&d->cqm_limbo);
-			cqm_setup_limbo_handler(d, 0, RESCTRL_PICK_ANY_CPU);
-		}
-	}
 }
 
 static void clear_closid_rmid(int cpu)
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index f06a80d8fa3b..1eb1c9b4aec7 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -3890,7 +3890,9 @@ static void clear_childcpus(struct rdtgroup *r, unsigned int cpu)
 
 void resctrl_offline_cpu(unsigned int cpu)
 {
+	struct rdt_resource *l3 = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
 	struct rdtgroup *rdtgrp;
+	struct rdt_domain *d;
 
 	lockdep_assert_held(&rdtgroup_mutex);
 
@@ -3900,6 +3902,22 @@ void resctrl_offline_cpu(unsigned int cpu)
 			break;
 		}
 	}
+
+	if (!l3->mon_capable)
+		return;
+
+	d = get_domain_from_cpu(cpu, l3);
+	if (d) {
+		if (is_mbm_enabled() && cpu == d->mbm_work_cpu) {
+			cancel_delayed_work(&d->mbm_over);
+			mbm_setup_overflow_handler(d, 0, cpu);
+		}
+		if (is_llc_occupancy_enabled() && cpu == d->cqm_work_cpu &&
+		    has_busy_rmid(d)) {
+			cancel_delayed_work(&d->cqm_limbo);
+			cqm_setup_limbo_handler(d, 0, cpu);
+		}
+	}
 }
 
 /*
-- 
2.39.2