linux-kernel - [tip: x86/boot] x86/fpu: Move FPU initialization into arch_cpu_finalize

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Message-ID: <168690748113.404.13314023725457189436.tip-bot2@tip-bot2>
Date:   Fri, 16 Jun 2023 09:24:41 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/boot] x86/fpu: Move FPU initialization into
 arch_cpu_finalize_init()

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

Commit-ID:     b81fac906a8f9e682e513ddd95697ec7a20878d4
Gitweb:        https://git.kernel.org/tip/b81fac906a8f9e682e513ddd95697ec7a20878d4
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Wed, 14 Jun 2023 01:39:46 +02:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Fri, 16 Jun 2023 10:16:01 +02:00

x86/fpu: Move FPU initialization into arch_cpu_finalize_init()

Initializing the FPU during the early boot process is a pointless
exercise. Early boot is convoluted and fragile enough.

Nothing requires that the FPU is set up early. It has to be initialized
before fork_init() because the task_struct size depends on the FPU register
buffer size.

Move the initialization to arch_cpu_finalize_init() which is the perfect
place to do so.

No functional change.

This allows to remove quite some of the custom early command line parsing,
but that's subject to the next installment.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Link: https://lore.kernel.org/r/20230613224545.902376621@linutronix.de

---
 arch/x86/kernel/cpu/common.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 2807e5b..46ebdd6 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1604,8 +1604,6 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 
 	sld_setup(c);
 
-	fpu__init_system();
-
 #ifdef CONFIG_X86_32
 	/*
 	 * Regardless of whether PCID is enumerated, the SDM says
@@ -2287,8 +2285,6 @@ void cpu_init(void)
 
 	doublefault_init_cpu_tss();
 
-	fpu__init_cpu();
-
 	if (is_uv_system())
 		uv_cpu_init();
 
@@ -2304,6 +2300,7 @@ void cpu_init_secondary(void)
 	 */
 	cpu_init_exception_handling();
 	cpu_init();
+	fpu__init_cpu();
 }
 #endif
 
@@ -2396,6 +2393,13 @@ void __init arch_cpu_finalize_init(void)
 			'0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
 	}
 
+	/*
+	 * Must be before alternatives because it might set or clear
+	 * feature bits.
+	 */
+	fpu__init_system();
+	fpu__init_cpu();
+
 	alternative_instructions();
 
 	if (IS_ENABLED(CONFIG_X86_64)) {