linux-kernel - [tip: x86/apic] x86/cpu/topology: Simplify cpu_mark_primary

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Date: Fri, 16 Feb 2024 15:16:50 -0000
From: "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
 Michael Kelley <mhklinux@...look.com>, Sohil Mehta <sohil.mehta@...el.com>,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/apic] x86/cpu/topology: Simplify cpu_mark_primary_thread()

The following commit has been merged into the x86/apic branch of tip:

Commit-ID:     5e40fb2d4a4c7503cab4f923b7d985dbcf583581
Gitweb:        https://git.kernel.org/tip/5e40fb2d4a4c7503cab4f923b7d985dbcf583581
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Tue, 13 Feb 2024 22:06:06 +01:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Thu, 15 Feb 2024 22:07:44 +01:00

x86/cpu/topology: Simplify cpu_mark_primary_thread()

No point in creating a mask via fls(). smp_num_siblings is guaranteed to be
a power of 2. So just using (smp_num_siblings - 1) has the same effect.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Michael Kelley <mhklinux@...look.com>
Tested-by: Sohil Mehta <sohil.mehta@...el.com>
Link: https://lore.kernel.org/r/20240213210252.791176581@linutronix.de





---
 arch/x86/kernel/cpu/topology.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c
index f3397e2..aea408d 100644
--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -76,10 +76,7 @@ bool arch_match_cpu_phys_id(int cpu, u64 phys_id)
 #ifdef CONFIG_SMP
 static void cpu_mark_primary_thread(unsigned int cpu, unsigned int apicid)
 {
-	/* Isolate the SMT bit(s) in the APICID and check for 0 */
-	u32 mask = (1U << (fls(smp_num_siblings) - 1)) - 1;
-
-	if (smp_num_siblings == 1 || !(apicid & mask))
+	if (!(apicid & (smp_num_siblings - 1)))
 		cpumask_set_cpu(cpu, &__cpu_primary_thread_mask);
 }
 #else