linux-kernel - [PATCH v2 4/9] cpu/SMT: Remove topology_smt

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Date:   Wed, 28 Jun 2023 12:05:53 +0200
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        mpe@...erman.id.au, npiggin@...il.com, christophe.leroy@...roup.eu,
        tglx@...utronix.de, dave.hansen@...ux.intel.com, mingo@...hat.com,
        bp@...en8.de
Subject: [PATCH v2 4/9] cpu/SMT: Remove topology_smt_supported()

Since the maximum number of threads is now passed to
cpu_smt_set_num_threads(), checking that value is enough to know if SMT is
supported.

Cc: Michael Ellerman <mpe@...erman.id.au>
Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Laurent Dufour <ldufour@...ux.ibm.com>
---
 arch/x86/include/asm/topology.h | 2 --
 arch/x86/kernel/smpboot.c       | 8 --------
 kernel/cpu.c                    | 2 +-
 3 files changed, 1 insertion(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
index 66927a59e822..87358a8fe843 100644
--- a/arch/x86/include/asm/topology.h
+++ b/arch/x86/include/asm/topology.h
@@ -143,7 +143,6 @@ int topology_update_die_map(unsigned int dieid, unsigned int cpu);
 int topology_phys_to_logical_pkg(unsigned int pkg);
 int topology_phys_to_logical_die(unsigned int die, unsigned int cpu);
 bool topology_is_primary_thread(unsigned int cpu);
-bool topology_smt_supported(void);
 #else
 #define topology_max_packages()			(1)
 static inline int
@@ -156,7 +155,6 @@ static inline int topology_phys_to_logical_die(unsigned int die,
 static inline int topology_max_die_per_package(void) { return 1; }
 static inline int topology_max_smt_threads(void) { return 1; }
 static inline bool topology_is_primary_thread(unsigned int cpu) { return true; }
-static inline bool topology_smt_supported(void) { return false; }
 #endif
 
 static inline void arch_fix_phys_package_id(int num, u32 slot)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 352f0ce1ece4..3052c171668d 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -278,14 +278,6 @@ bool topology_is_primary_thread(unsigned int cpu)
 	return apic_id_is_primary_thread(per_cpu(x86_cpu_to_apicid, cpu));
 }
 
-/**
- * topology_smt_supported - Check whether SMT is supported by the CPUs
- */
-bool topology_smt_supported(void)
-{
-	return smp_num_siblings > 1;
-}
-
 /**
  * topology_phys_to_logical_pkg - Map a physical package id to a logical
  *
diff --git a/kernel/cpu.c b/kernel/cpu.c
index edca8b7bd400..e354af92b2b8 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -442,7 +442,7 @@ void __init cpu_smt_set_num_threads(unsigned int num_threads,
 {
 	WARN_ON(!num_threads || (num_threads > max_threads));
 
-	if (!topology_smt_supported())
+	if (max_threads == 1)
 		cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
 
 	cpu_smt_max_threads = max_threads;
-- 
2.41.0