From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 21 Jun 2018 08:37:20 +0000 (+0200)
Subject: x86/topology: Provide topology_smt_supported()
X-Git-Tag: v4.1.12-124.31.3~661
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=870a86602753f83a6e8c552a3c1ea7ba0670efaa;p=users%2Fjedix%2Flinux-maple.git

x86/topology: Provide topology_smt_supported()

Provide information whether SMT is supoorted by the CPUs. Preparatory patch
for SMT control mechanism.

Suggested-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@kernel.org>

Orabug: 28220674
CVE: CVE-2018-3620

(cherry picked from commit f048c399e0f7490ab7296bc2c255d37eb14a9675)

Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

Conflicts:
	arch/x86/kernel/smpboot.c
Contextual
---

diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
index bf9b53421a6f7..0d02e19abe581 100644
--- a/arch/x86/include/asm/topology.h
+++ b/arch/x86/include/asm/topology.h
@@ -124,8 +124,10 @@ extern const struct cpumask *cpu_coregroup_mask(int cpu);
 
 #ifdef CONFIG_SMP
 bool topology_is_primary_thread(unsigned int cpu);
+bool topology_smt_supported(void);
 #else
 static inline bool topology_is_primary_thread(unsigned int cpu) { return true; }
+static inline bool topology_smt_supported(void) { return false; }
 #endif
 
 #ifdef ENABLE_TOPO_DEFINES
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 76c42a0d26c40..9cf20ce8be2dc 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -279,6 +279,14 @@ 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;
+}
+
 void __init smp_store_boot_cpu_info(void)
 {
 	int id = 0; /* CPU 0 */