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Date:   Tue, 16 May 2023 09:10:01 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@linutronix.de>
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Subject: [tip: smp/core] x86/smpboot: Get rid of cpu_init_secondary()
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Michael Kelley <mikelley@microsoft.com>,
        Oleksandr Natalenko <oleksandr@natalenko.name>,
        Helge Deller <deller@gmx.de>,
        "Guilherme G. Piccoli" <gpiccoli@igalia.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org
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The following commit has been merged into the smp/core branch of tip:

Commit-ID:     e94cd1503b153ea753f0c4ed9d5ed12e7abd1306
Gitweb:        https://git.kernel.org/tip/e94cd1503b153ea753f0c4ed9d5ed12e7abd1306
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Fri, 12 May 2023 23:07:12 +02:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 15 May 2023 13:44:51 +02:00

x86/smpboot: Get rid of cpu_init_secondary()

The synchronization of the AP with the control CPU is a SMP boot problem
and has nothing to do with cpu_init().

Open code cpu_init_secondary() in start_secondary() and move
wait_for_master_cpu() into the SMP boot code.

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> # Steam Deck
Link: https://lore.kernel.org/r/20230512205255.981999763@linutronix.de
---
 arch/x86/include/asm/processor.h |  1 -
 arch/x86/kernel/cpu/common.c     | 27 ---------------------------
 arch/x86/kernel/smpboot.c        | 24 +++++++++++++++++++-----
 3 files changed, 19 insertions(+), 33 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index a1e4fa5..d46300e 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -551,7 +551,6 @@ extern void switch_gdt_and_percpu_base(int);
 extern void load_direct_gdt(int);
 extern void load_fixmap_gdt(int);
 extern void cpu_init(void);
-extern void cpu_init_secondary(void);
 extern void cpu_init_exception_handling(void);
 extern void cr4_init(void);
 
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 80710a6..e25fb13 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2123,19 +2123,6 @@ static void dbg_restore_debug_regs(void)
 #define dbg_restore_debug_regs()
 #endif /* ! CONFIG_KGDB */
 
-static void wait_for_master_cpu(int cpu)
-{
-#ifdef CONFIG_SMP
-	/*
-	 * wait for ACK from master CPU before continuing
-	 * with AP initialization
-	 */
-	WARN_ON(cpumask_test_and_set_cpu(cpu, cpu_initialized_mask));
-	while (!cpumask_test_cpu(cpu, cpu_callout_mask))
-		cpu_relax();
-#endif
-}
-
 static inline void setup_getcpu(int cpu)
 {
 	unsigned long cpudata = vdso_encode_cpunode(cpu, early_cpu_to_node(cpu));
@@ -2239,8 +2226,6 @@ void cpu_init(void)
 	struct task_struct *cur = current;
 	int cpu = raw_smp_processor_id();
 
-	wait_for_master_cpu(cpu);
-
 	ucode_cpu_init(cpu);
 
 #ifdef CONFIG_NUMA
@@ -2293,18 +2278,6 @@ void cpu_init(void)
 	load_fixmap_gdt(cpu);
 }
 
-#ifdef CONFIG_SMP
-void cpu_init_secondary(void)
-{
-	/*
-	 * Relies on the BP having set-up the IDT tables, which are loaded
-	 * on this CPU in cpu_init_exception_handling().
-	 */
-	cpu_init_exception_handling();
-	cpu_init();
-}
-#endif
-
 #ifdef CONFIG_MICROCODE_LATE_LOADING
 /**
  * store_cpu_caps() - Store a snapshot of CPU capabilities
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 0bd9c9f..50eff9b 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -220,6 +220,17 @@ static void ap_calibrate_delay(void)
 	cpu_data(smp_processor_id()).loops_per_jiffy = loops_per_jiffy;
 }
 
+static void wait_for_master_cpu(int cpu)
+{
+	/*
+	 * Wait for release by control CPU before continuing with AP
+	 * initialization.
+	 */
+	WARN_ON(cpumask_test_and_set_cpu(cpu, cpu_initialized_mask));
+	while (!cpumask_test_cpu(cpu, cpu_callout_mask))
+		cpu_relax();
+}
+
 /*
  * Activate a secondary processor.
  */
@@ -237,13 +248,16 @@ static void notrace start_secondary(void *unused)
 	load_cr3(swapper_pg_dir);
 	__flush_tlb_all();
 #endif
+	cpu_init_exception_handling();
+
 	/*
-	 * Sync point with wait_cpu_initialized(). Before proceeding through
-	 * cpu_init(), the AP will call wait_for_master_cpu() which sets its
-	 * own bit in cpu_initialized_mask and then waits for the BSP to set
-	 * its bit in cpu_callout_mask to release it.
+	 * Sync point with wait_cpu_initialized(). Sets AP in
+	 * cpu_initialized_mask and then waits for the control CPU
+	 * to release it.
 	 */
-	cpu_init_secondary();
+	wait_for_master_cpu(raw_smp_processor_id());
+
+	cpu_init();
 	rcu_cpu_starting(raw_smp_processor_id());
 	x86_cpuinit.early_percpu_clock_init();