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x86/microcode: Add per CPU result state

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The microcode rendezvous is purely acting on global state, which does
not allow to analyze fails in a coherent way.

Introduce per CPU state where the results are written into, which allows to
analyze the return codes of the individual CPUs.

Initialize the state when walking the cpu_present_mask in the online
check to avoid another for_each_cpu() loop.

Enhance the result print out with that.

The structure is intentionally named ucode_ctrl as it will gain control
fields in subsequent changes.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20231017211723.632681010@linutronix.de
This commit is contained in:
Thomas Gleixner 2023-10-17 23:24:05 +02:00 committed by Borislav Petkov (AMD)
parent 0772b9aa1a
commit 4b753955e9
2 changed files with 67 additions and 46 deletions
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112
arch/x86/kernel/cpu/microcode/core.c
View File

@ -252,6 +252,11 @@ static struct platform_device *microcode_pdev;
* requirement can be relaxed in the future. Right now, this is conservative
* and good.
*/
struct microcode_ctrl {
enum ucode_state result;
};
static DEFINE_PER_CPU(struct microcode_ctrl, ucode_ctrl);
static atomic_t late_cpus_in, late_cpus_out;
static bool wait_for_cpus(atomic_t *cnt)
@ -274,23 +279,19 @@ static bool wait_for_cpus(atomic_t *cnt)
return false;
}
/*
* Returns:
* < 0 - on error
* 0 - success (no update done or microcode was updated)
*/
static int __reload_late(void *info)
static int load_cpus_stopped(void *unused)
{
int cpu = smp_processor_id();
enum ucode_state err;
int ret = 0;
enum ucode_state ret;
/*
* Wait for all CPUs to arrive. A load will not be attempted unless all
* CPUs show up.
* */
if (!wait_for_cpus(&late_cpus_in))
return -1;
if (!wait_for_cpus(&late_cpus_in)) {
this_cpu_write(ucode_ctrl.result, UCODE_TIMEOUT);
return 0;
}
/*
* On an SMT system, it suffices to load the microcode on one sibling of
@ -299,17 +300,11 @@ static int __reload_late(void *info)
* loading attempts happen on multiple threads of an SMT core. See
* below.
*/
if (cpumask_first(topology_sibling_cpumask(cpu)) == cpu)
err = microcode_ops->apply_microcode(cpu);
else
if (cpumask_first(topology_sibling_cpumask(cpu)) != cpu)
goto wait_for_siblings;
if (err >= UCODE_NFOUND) {
if (err == UCODE_ERROR) {
pr_warn("Error reloading microcode on CPU %d\n", cpu);
ret = -1;
}
}
ret = microcode_ops->apply_microcode(cpu);
this_cpu_write(ucode_ctrl.result, ret);
wait_for_siblings:
if (!wait_for_cpus(&late_cpus_out))
@ -321,19 +316,18 @@ wait_for_siblings:
* per-cpu cpuinfo can be updated with right microcode
* revision.
*/
if (cpumask_first(topology_sibling_cpumask(cpu)) != cpu)
err = microcode_ops->apply_microcode(cpu);
if (cpumask_first(topology_sibling_cpumask(cpu)) == cpu)
return 0;
return ret;
ret = microcode_ops->apply_microcode(cpu);
this_cpu_write(ucode_ctrl.result, ret);
return 0;
}
/*
* Reload microcode late on all CPUs. Wait for a sec until they
* all gather together.
*/
static int microcode_reload_late(void)
static int load_late_stop_cpus(void)
{
int old = boot_cpu_data.microcode, ret;
unsigned int cpu, updated = 0, failed = 0, timedout = 0, siblings = 0;
int old_rev = boot_cpu_data.microcode;
struct cpuinfo_x86 prev_info;
pr_err("Attempting late microcode loading - it is dangerous and taints the kernel.\n");
@ -348,26 +342,47 @@ static int microcode_reload_late(void)
*/
store_cpu_caps(&prev_info);
ret = stop_machine_cpuslocked(__reload_late, NULL, cpu_online_mask);
stop_machine_cpuslocked(load_cpus_stopped, NULL, cpu_online_mask);
/* Analyze the results */
for_each_cpu_and(cpu, cpu_present_mask, &cpus_booted_once_mask) {
switch (per_cpu(ucode_ctrl.result, cpu)) {
case UCODE_UPDATED: updated++; break;
case UCODE_TIMEOUT: timedout++; break;
case UCODE_OK: siblings++; break;
default: failed++; break;
}
}
if (microcode_ops->finalize_late_load)
microcode_ops->finalize_late_load(ret);
microcode_ops->finalize_late_load(!updated);
if (!ret) {
pr_info("Reload succeeded, microcode revision: 0x%x -> 0x%x\n",
old, boot_cpu_data.microcode);
microcode_check(&prev_info);
add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);
} else {
pr_info("Reload failed, current microcode revision: 0x%x\n",
boot_cpu_data.microcode);
if (!updated) {
/* Nothing changed. */
if (!failed && !timedout)
return 0;
pr_err("update failed: %u CPUs failed %u CPUs timed out\n",
failed, timedout);
return -EIO;
}
return ret;
add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);
pr_info("load: updated on %u primary CPUs with %u siblings\n", updated, siblings);
if (failed || timedout) {
pr_err("load incomplete. %u CPUs timed out or failed\n",
num_online_cpus() - (updated + siblings));
}
pr_info("revision: 0x%x -> 0x%x\n", old_rev, boot_cpu_data.microcode);
microcode_check(&prev_info);
return updated + siblings == num_online_cpus() ? 0 : -EIO;
}
/*
* Ensure that all required CPUs which are present and have been booted
* once are online.
* This function does two things:
*
* 1) Ensure that all required CPUs which are present and have been booted
* once are online.
*
* To pass this check, all primary threads must be online.
*
@ -378,9 +393,12 @@ static int microcode_reload_late(void)
* behaviour is undefined. The default play_dead() implementation on
* modern CPUs uses MWAIT, which is also not guaranteed to be safe
* against a microcode update which affects MWAIT.
*
* 2) Initialize the per CPU control structure
*/
static bool ensure_cpus_are_online(void)
static bool setup_cpus(void)
{
struct microcode_ctrl ctrl = { .result = -1, };
unsigned int cpu;
for_each_cpu_and(cpu, cpu_present_mask, &cpus_booted_once_mask) {
@ -390,18 +408,20 @@ static bool ensure_cpus_are_online(void)
return false;
}
}
/* Initialize the per CPU state */
per_cpu(ucode_ctrl, cpu) = ctrl;
}
return true;
}
static int ucode_load_late_locked(void)
static int load_late_locked(void)
{
if (!ensure_cpus_are_online())
if (!setup_cpus())
return -EBUSY;
switch (microcode_ops->request_microcode_fw(0, &microcode_pdev->dev)) {
case UCODE_NEW:
return microcode_reload_late();
return load_late_stop_cpus();
case UCODE_NFOUND:
return -ENOENT;
default:
@ -421,7 +441,7 @@ static ssize_t reload_store(struct device *dev,
return -EINVAL;
cpus_read_lock();
ret = ucode_load_late_locked();
ret = load_late_locked();
cpus_read_unlock();
return ret ? : size;

1
arch/x86/kernel/cpu/microcode/internal.h
View File

@ -16,6 +16,7 @@ enum ucode_state {
UCODE_UPDATED,
UCODE_NFOUND,
UCODE_ERROR,
UCODE_TIMEOUT,
};
struct microcode_ops {