linux-kernel - [PATCH AUTOSEL for 4.9 38/50] s390/topology: make "topology=off" parameter work

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Message-ID: <20171025015539.24525-38-alexander.levin@verizon.com>
Date:   Wed, 25 Oct 2017 01:56:01 +0000
From:   "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Heiko Carstens <heiko.carstens@...ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
Subject: [PATCH AUTOSEL for 4.9 38/50] s390/topology: make "topology=off"
 parameter work

From: Heiko Carstens <heiko.carstens@...ibm.com>

[ Upstream commit 68cc795d1933285705ced6d841ef66c00ce98cbe ]

The "topology=off" kernel parameter is supposed to prevent the kernel
to use hardware topology information to generate scheduling domains
etc.
For an unknown reason I implemented this in a very odd way back then:
instead of simply clearing the MACHINE_HAS_TOPOLOGY flag within the
lowcore I added a second variable which indicated that topology
information should not be used. This is more than suboptimal since it
partially doesn't work.  For the fake NUMA case topology information
is still considered and scheduling domains will be created based on
this.
To fix this and to simplify the code get rid of the extra variable and
implement the "topology=off" case like it is done for other features.

Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 arch/s390/kernel/early.c    | 12 ++++++++++++
 arch/s390/kernel/topology.c | 11 ++---------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
index 2374c5b46bbc..0c196861bc38 100644
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -363,6 +363,18 @@ static inline void save_vector_registers(void)
 #endif
 }
 
+static int __init topology_setup(char *str)
+{
+	bool enabled;
+	int rc;
+
+	rc = kstrtobool(str, &enabled);
+	if (!rc && !enabled)
+		S390_lowcore.machine_flags &= ~MACHINE_HAS_TOPOLOGY;
+	return rc;
+}
+early_param("topology", topology_setup);
+
 static int __init disable_vector_extension(char *str)
 {
 	S390_lowcore.machine_flags &= ~MACHINE_FLAG_VX;
diff --git a/arch/s390/kernel/topology.c b/arch/s390/kernel/topology.c
index 8705ee66c087..239f29508f0b 100644
--- a/arch/s390/kernel/topology.c
+++ b/arch/s390/kernel/topology.c
@@ -37,7 +37,6 @@ static void set_topology_timer(void);
 static void topology_work_fn(struct work_struct *work);
 static struct sysinfo_15_1_x *tl_info;
 
-static bool topology_enabled = true;
 static DECLARE_WORK(topology_work, topology_work_fn);
 
 /*
@@ -56,7 +55,7 @@ static cpumask_t cpu_group_map(struct mask_info *info, unsigned int cpu)
 	cpumask_t mask;
 
 	cpumask_copy(&mask, cpumask_of(cpu));
-	if (!topology_enabled || !MACHINE_HAS_TOPOLOGY)
+	if (!MACHINE_HAS_TOPOLOGY)
 		return mask;
 	for (; info; info = info->next) {
 		if (cpumask_test_cpu(cpu, &info->mask))
@@ -71,7 +70,7 @@ static cpumask_t cpu_thread_map(unsigned int cpu)
 	int i;
 
 	cpumask_copy(&mask, cpumask_of(cpu));
-	if (!topology_enabled || !MACHINE_HAS_TOPOLOGY)
+	if (!MACHINE_HAS_TOPOLOGY)
 		return mask;
 	cpu -= cpu % (smp_cpu_mtid + 1);
 	for (i = 0; i <= smp_cpu_mtid; i++)
@@ -413,12 +412,6 @@ static const struct cpumask *cpu_drawer_mask(int cpu)
 	return &per_cpu(cpu_topology, cpu).drawer_mask;
 }
 
-static int __init early_parse_topology(char *p)
-{
-	return kstrtobool(p, &topology_enabled);
-}
-early_param("topology", early_parse_topology);
-
 static struct sched_domain_topology_level s390_topology[] = {
 	{ cpu_thread_mask, cpu_smt_flags, SD_INIT_NAME(SMT) },
 	{ cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) },
-- 
2.11.0