x86/fpu: Move FPU initialization into arch_cpu_finalize_init()

commit b81fac906a8f9e682e513ddd95697ec7a20878d4 upstream

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@linutronix.de>
Link: https://lore.kernel.org/r/20230613224545.902376621@linutronix.de
Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 5501b817d5010098aed4b1061afeef5c2abacfee..284c4156aacea4f3b0be966a3f0bbcb50e4e02d3 100644 (file)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1364,8 +1364,6 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 
        cpu_set_bug_bits(c);
 
-       fpu__init_system();
-
 #ifdef CONFIG_X86_32
        /*
         * Regardless of whether PCID is enumerated, the SDM says
@@ -2055,8 +2053,6 @@ void cpu_init(void)
        clear_all_debug_regs();
        dbg_restore_debug_regs();
 
-       fpu__init_cpu();
-
        if (is_uv_system())
                uv_cpu_init();
 
@@ -2114,8 +2110,6 @@ void cpu_init(void)
        clear_all_debug_regs();
        dbg_restore_debug_regs();
 
-       fpu__init_cpu();
-
        load_fixmap_gdt(cpu);
 }
 #endif
@@ -2194,6 +2188,13 @@ 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)) {

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 45e5ecb43393bf4c9860951e0d6060db75f0763e..d6a8efff9c617f9847eb97d2942a6547894a78d4 100644 (file)
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -235,6 +235,7 @@ static void notrace start_secondary(void *unused)
 #endif
        load_current_idt();
        cpu_init();
+       fpu__init_cpu();
        rcu_cpu_starting(raw_smp_processor_id());
        x86_cpuinit.early_percpu_clock_init();
        preempt_disable();