From: "tip-bot2 for Balbir Singh" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
Balbir Singh <sblbir@amazon.com>, x86 <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: [tip: x86/pti] x86/smp: Add a per-cpu view of SMT state
Date: Wed, 16 Sep 2020 13:11:20 -0000 [thread overview]
Message-ID: <160026188050.15536.7745071933237655912.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20200729001103.6450-2-sblbir@amazon.com>
The following commit has been merged into the x86/pti branch of tip:
Commit-ID: 0a260b1c5867863121b044afa8087d6b37e4fb7d
Gitweb: https://git.kernel.org/tip/0a260b1c5867863121b044afa8087d6b37e4fb7d
Author: Balbir Singh <sblbir@amazon.com>
AuthorDate: Wed, 29 Jul 2020 10:10:59 +10:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Wed, 16 Sep 2020 15:08:02 +02:00
x86/smp: Add a per-cpu view of SMT state
A new field smt_active in cpuinfo_x86 identifies if the current core/cpu
is in SMT mode or not. This can be very helpful if the system has some
of its cores with threads offlined and can be used for cases where
action is taken based on the state of SMT. The follow up patches use
this feature.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Balbir Singh <sblbir@amazon.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20200729001103.6450-2-sblbir@amazon.com
---
arch/x86/include/asm/processor.h | 2 ++
arch/x86/kernel/smpboot.c | 11 ++++++++++-
2 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 97143d8..d9eb20f 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -136,6 +136,8 @@ struct cpuinfo_x86 {
u16 logical_die_id;
/* Index into per_cpu list: */
u16 cpu_index;
+ /* Is SMT active on this core? */
+ bool smt_active;
u32 microcode;
/* Address space bits used by the cache internally */
u8 x86_cache_bits;
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index f5ef689..5fc7e0e 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -635,6 +635,9 @@ void set_cpu_sibling_map(int cpu)
threads = cpumask_weight(topology_sibling_cpumask(cpu));
if (threads > __max_smt_threads)
__max_smt_threads = threads;
+
+ for_each_cpu(i, topology_sibling_cpumask(cpu))
+ cpu_data(i).smt_active = threads > 1;
}
/* maps the cpu to the sched domain representing multi-core */
@@ -1548,10 +1551,16 @@ static void remove_siblinginfo(int cpu)
for_each_cpu(sibling, topology_die_cpumask(cpu))
cpumask_clear_cpu(cpu, topology_die_cpumask(sibling));
- for_each_cpu(sibling, topology_sibling_cpumask(cpu))
+
+ for_each_cpu(sibling, topology_sibling_cpumask(cpu)) {
cpumask_clear_cpu(cpu, topology_sibling_cpumask(sibling));
+ if (cpumask_weight(topology_sibling_cpumask(sibling)) == 1)
+ cpu_data(sibling).smt_active = false;
+ }
+
for_each_cpu(sibling, cpu_llc_shared_mask(cpu))
cpumask_clear_cpu(cpu, cpu_llc_shared_mask(sibling));
+
cpumask_clear(cpu_llc_shared_mask(cpu));
cpumask_clear(topology_sibling_cpumask(cpu));
cpumask_clear(topology_core_cpumask(cpu));
next prev parent reply other threads:[~2020-09-16 20:27 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-29 0:10 [PATCH v2 0/5] Implement optional L1D flushing for Balbir Singh
2020-07-29 0:10 ` [PATCH v2 1/5] Add a per-cpu view of SMT state Balbir Singh
2020-09-16 13:11 ` tip-bot2 for Balbir Singh [this message]
2020-07-29 0:11 ` [PATCH v2 2/5] x86/mm: Refactor cond_ibpb() to support other use cases Balbir Singh
2020-07-29 0:11 ` [PATCH v2 3/5] x86/mm: Optionally flush L1D on context switch Balbir Singh
2020-09-16 13:11 ` [tip: x86/pti] " tip-bot2 for Balbir Singh
2020-07-29 0:11 ` [PATCH v2 4/5] prctl: Hook L1D flushing in via prctl Balbir Singh
2020-07-29 13:14 ` Tom Lendacky
2020-07-30 0:13 ` Singh, Balbir
2020-09-16 13:11 ` [tip: x86/pti] " tip-bot2 for Balbir Singh
2020-07-29 0:11 ` [PATCH v2 5/5] Documentation: Add L1D flushing Documentation Balbir Singh
2020-09-16 13:11 ` [tip: x86/pti] " tip-bot2 for Balbir Singh
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