x86/cpu: Ensure that CPU info updates are propagated on UP
The boot sequence evaluates CPUID information twice:
1) During early boot
2) When finalizing the early setup right before
mitigations are selected and alternatives are patched.
In both cases the evaluation is stored in boot_cpu_data, but on UP the
copying of boot_cpu_data to the per CPU info of the boot CPU happens
between #1 and #2. So any update which happens in #2 is never propagated to
the per CPU info instance.
Consolidate the whole logic and copy boot_cpu_data right before applying
alternatives as that's the point where boot_cpu_data is in it's final
state and not supposed to change anymore.
This also removes the voodoo mb() from smp_prepare_cpus_common() which
had absolutely no purpose.
Fixes: 71eb4893cfaf ("x86/percpu: Cure per CPU madness on UP")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20240322185305.127642785@linutronix.de
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index ba8cf5e..5c1e6d6 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2307,6 +2307,8 @@
void __init arch_cpu_finalize_init(void)
{
+ struct cpuinfo_x86 *c = this_cpu_ptr(&cpu_info);
+
identify_boot_cpu();
select_idle_routine();
@@ -2345,6 +2347,13 @@
fpu__init_system();
fpu__init_cpu();
+ /*
+ * Ensure that access to the per CPU representation has the initial
+ * boot CPU configuration.
+ */
+ *c = boot_cpu_data;
+ c->initialized = true;
+
alternative_instructions();
if (IS_ENABLED(CONFIG_X86_64)) {
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 3e1e96e..ef20650 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1206,16 +1206,6 @@
#endif /* CONFIG_X86_32 */
-#ifndef CONFIG_SMP
-void __init smp_prepare_boot_cpu(void)
-{
- struct cpuinfo_x86 *c = &cpu_data(0);
-
- *c = boot_cpu_data;
- c->initialized = true;
-}
-#endif
-
static struct notifier_block kernel_offset_notifier = {
.notifier_call = dump_kernel_offset
};
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index fe355c8..76bb650 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -313,14 +313,6 @@
cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
}
-static void __init smp_store_boot_cpu_info(void)
-{
- struct cpuinfo_x86 *c = &cpu_data(0);
-
- *c = boot_cpu_data;
- c->initialized = true;
-}
-
/*
* The bootstrap kernel entry code has set these up. Save them for
* a given CPU
@@ -1039,29 +1031,15 @@
cpumask_set_cpu(0, topology_die_cpumask(0));
}
-static void __init smp_cpu_index_default(void)
-{
- int i;
- struct cpuinfo_x86 *c;
-
- for_each_possible_cpu(i) {
- c = &cpu_data(i);
- /* mark all to hotplug */
- c->cpu_index = nr_cpu_ids;
- }
-}
-
void __init smp_prepare_cpus_common(void)
{
unsigned int i;
- smp_cpu_index_default();
-
- /*
- * Setup boot CPU information
- */
- smp_store_boot_cpu_info(); /* Final full version of the data */
- mb();
+ /* Mark all except the boot CPU as hotpluggable */
+ for_each_possible_cpu(i) {
+ if (i)
+ per_cpu(cpu_info.cpu_index, i) = nr_cpu_ids;
+ }
for_each_possible_cpu(i) {
zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
