Skip to content

Commit

Permalink
x86/cpu: Ensure that CPU info updates are propagated on UP
Browse files Browse the repository at this point in the history
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: 71eb489 ("x86/percpu: Cure per CPU madness on UP")
Reported-by: Guenter Roeck <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Tested-by: Guenter Roeck <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
  • Loading branch information
KAGA-KOKO authored and bp3tk0v committed Mar 23, 2024
1 parent 4e51653 commit c90399f
Show file tree
Hide file tree
Showing 3 changed files with 14 additions and 37 deletions.
9 changes: 9 additions & 0 deletions arch/x86/kernel/cpu/common.c
Original file line number Diff line number Diff line change
Expand Up @@ -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();
Expand Down Expand Up @@ -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)) {
Expand Down
10 changes: 0 additions & 10 deletions arch/x86/kernel/setup.c
Original file line number Diff line number Diff line change
Expand Up @@ -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
};
Expand Down
32 changes: 5 additions & 27 deletions arch/x86/kernel/smpboot.c
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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);
Expand Down

0 comments on commit c90399f

Please sign in to comment.