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x86/cpu: Ensure that CPU info updates are propagated on UP

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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: 71eb4893cf ("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
This commit is contained in:
Thomas Gleixner 2024-03-22 19:56:35 +01:00 committed by Borislav Petkov (AMD)
parent 4e51653d5d
commit c90399fbd7
3 changed files with 14 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
arch/x86/kernel/cpu/common.c
View File

@ -2307,6 +2307,8 @@ void arch_smt_update(void)
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 @@ void __init arch_cpu_finalize_init(void)
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)) {

10
arch/x86/kernel/setup.c
View File

@ -1206,16 +1206,6 @@ void __init i386_reserve_resources(void)
#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
};

32
arch/x86/kernel/smpboot.c
View File

@ -313,14 +313,6 @@ static void notrace start_secondary(void *unused)
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 @@ static __init void disable_smp(void)
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);