1 files changed, 455 insertions, 393 deletions

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index ad57e0e4d674..232026a239a6 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -23,6 +23,7 @@
 #include <linux/miscdevice.h>
 #include <linux/capability.h>
 #include <linux/firmware.h>
+#include <linux/cpumask.h>
 #include <linux/kernel.h>
 #include <linux/delay.h>
 #include <linux/mutex.h>
@@ -31,38 +32,32 @@
 #include <linux/fs.h>
 #include <linux/mm.h>
 
-#include <asm/microcode_intel.h>
+#include <asm/apic.h>
 #include <asm/cpu_device_id.h>
-#include <asm/microcode_amd.h>
 #include <asm/perf_event.h>
-#include <asm/microcode.h>
 #include <asm/processor.h>
 #include <asm/cmdline.h>
 #include <asm/setup.h>
 
-#define DRIVER_VERSION	"2.2"
+#include "internal.h"
 
 static struct microcode_ops	*microcode_ops;
-static bool dis_ucode_ldr = true;
+bool dis_ucode_ldr = true;
 
-bool initrd_gone;
-
-LIST_HEAD(microcode_cache);
+bool force_minrev = IS_ENABLED(CONFIG_MICROCODE_LATE_FORCE_MINREV);
+module_param(force_minrev, bool, S_IRUSR | S_IWUSR);
 
 /*
  * Synchronization.
  *
  * All non cpu-hotplug-callback call sites use:
  *
- * - microcode_mutex to synchronize with each other;
  * - cpus_read_lock/unlock() to synchronize with
  *   the cpu-hotplug-callback call sites.
  *
  * We guarantee that only a single cpu is being
  * updated at any particular moment of time.
  */
-static DEFINE_MUTEX(microcode_mutex);
-
 struct ucode_cpu_info		ucode_cpu_info[NR_CPUS];
 
 struct cpu_info_ctx {
@@ -80,6 +75,8 @@ static u32 final_levels[] = {
 	0, /* T-101 terminator */
 };
 
+struct early_load_data early_data;
+
 /*
  * Check the current patch level on this CPU.
  *
@@ -94,10 +91,7 @@ static bool amd_check_current_patch_level(void)
 
 	native_rdmsr(MSR_AMD64_PATCH_LEVEL, lvl, dummy);
 
-	if (IS_ENABLED(CONFIG_X86_32))
-		levels = (u32 *)__pa_nodebug(&final_levels);
-	else
-		levels = final_levels;
+	levels = final_levels;
 
 	for (i = 0; levels[i]; i++) {
 		if (lvl == levels[i])
@@ -109,17 +103,8 @@ static bool amd_check_current_patch_level(void)
 static bool __init check_loader_disabled_bsp(void)
 {
 	static const char *__dis_opt_str = "dis_ucode_ldr";
-
-#ifdef CONFIG_X86_32
-	const char *cmdline = (const char *)__pa_nodebug(boot_command_line);
-	const char *option  = (const char *)__pa_nodebug(__dis_opt_str);
-	bool *res = (bool *)__pa_nodebug(&dis_ucode_ldr);
-
-#else /* CONFIG_X86_64 */
 	const char *cmdline = boot_command_line;
 	const char *option  = __dis_opt_str;
-	bool *res = &dis_ucode_ldr;
-#endif
 
 	/*
 	 * CPUID(1).ECX[31]: reserved for hypervisor use. This is still not
@@ -127,17 +112,17 @@ static bool __init check_loader_disabled_bsp(void)
 	 * that's good enough as they don't land on the BSP path anyway.
 	 */
 	if (native_cpuid_ecx(1) & BIT(31))
-		return *res;
+		return true;
 
 	if (x86_cpuid_vendor() == X86_VENDOR_AMD) {
 		if (amd_check_current_patch_level())
-			return *res;
+			return true;
 	}
 
 	if (cmdline_find_option_bool(cmdline, option) <= 0)
-		*res = false;
+		dis_ucode_ldr = false;
 
-	return *res;
+	return dis_ucode_ldr;
 }
 
 void __init load_ucode_bsp(void)
@@ -170,25 +155,16 @@ void __init load_ucode_bsp(void)
 		return;
 
 	if (intel)
-		load_ucode_intel_bsp();
+		load_ucode_intel_bsp(&early_data);
 	else
-		load_ucode_amd_bsp(cpuid_1_eax);
-}
-
-static bool check_loader_disabled_ap(void)
-{
-#ifdef CONFIG_X86_32
-	return *((bool *)__pa_nodebug(&dis_ucode_ldr));
-#else
-	return dis_ucode_ldr;
-#endif
+		load_ucode_amd_bsp(&early_data, cpuid_1_eax);
 }
 
 void load_ucode_ap(void)
 {
 	unsigned int cpuid_1_eax;
 
-	if (check_loader_disabled_ap())
+	if (dis_ucode_ldr)
 		return;
 
 	cpuid_1_eax = native_cpuid_eax(1);
@@ -207,90 +183,37 @@ void load_ucode_ap(void)
 	}
 }
 
-static int __init save_microcode_in_initrd(void)
-{
-	struct cpuinfo_x86 *c = &boot_cpu_data;
-	int ret = -EINVAL;
-
-	switch (c->x86_vendor) {
-	case X86_VENDOR_INTEL:
-		if (c->x86 >= 6)
-			ret = save_microcode_in_initrd_intel();
-		break;
-	case X86_VENDOR_AMD:
-		if (c->x86 >= 0x10)
-			ret = save_microcode_in_initrd_amd(cpuid_eax(1));
-		break;
-	default:
-		break;
-	}
-
-	initrd_gone = true;
-
-	return ret;
-}
-
-struct cpio_data find_microcode_in_initrd(const char *path, bool use_pa)
+struct cpio_data __init find_microcode_in_initrd(const char *path)
 {
 #ifdef CONFIG_BLK_DEV_INITRD
 	unsigned long start = 0;
 	size_t size;
 
 #ifdef CONFIG_X86_32
-	struct boot_params *params;
-
-	if (use_pa)
-		params = (struct boot_params *)__pa_nodebug(&boot_params);
-	else
-		params = &boot_params;
-
-	size = params->hdr.ramdisk_size;
-
-	/*
-	 * Set start only if we have an initrd image. We cannot use initrd_start
-	 * because it is not set that early yet.
-	 */
+	size = boot_params.hdr.ramdisk_size;
+	/* Early load on BSP has a temporary mapping. */
 	if (size)
-		start = params->hdr.ramdisk_image;
+		start = initrd_start_early;
 
-# else /* CONFIG_X86_64 */
+#else /* CONFIG_X86_64 */
 	size  = (unsigned long)boot_params.ext_ramdisk_size << 32;
 	size |= boot_params.hdr.ramdisk_size;
 
 	if (size) {
 		start  = (unsigned long)boot_params.ext_ramdisk_image << 32;
 		start |= boot_params.hdr.ramdisk_image;
-
 		start += PAGE_OFFSET;
 	}
-# endif
+#endif
 
 	/*
 	 * Fixup the start address: after reserve_initrd() runs, initrd_start
 	 * has the virtual address of the beginning of the initrd. It also
 	 * possibly relocates the ramdisk. In either case, initrd_start contains
 	 * the updated address so use that instead.
-	 *
-	 * initrd_gone is for the hotplug case where we've thrown out initrd
-	 * already.
 	 */
-	if (!use_pa) {
-		if (initrd_gone)
-			return (struct cpio_data){ NULL, 0, "" };
-		if (initrd_start)
-			start = initrd_start;
-	} else {
-		/*
-		 * The picture with physical addresses is a bit different: we
-		 * need to get the *physical* address to which the ramdisk was
-		 * relocated, i.e., relocated_ramdisk (not initrd_start) and
-		 * since we're running from physical addresses, we need to access
-		 * relocated_ramdisk through its *physical* address too.
-		 */
-		u64 *rr = (u64 *)__pa_nodebug(&relocated_ramdisk);
-		if (*rr)
-			start = *rr;
-	}
+	if (initrd_start)
+		start = initrd_start;
 
 	return find_cpio_data(path, (void *)start, size, NULL);
 #else /* !CONFIG_BLK_DEV_INITRD */
@@ -298,7 +221,7 @@ struct cpio_data find_microcode_in_initrd(const char *path, bool use_pa)
 #endif
 }
 
-void reload_early_microcode(void)
+static void reload_early_microcode(unsigned int cpu)
 {
 	int vendor, family;
 
@@ -312,241 +235,483 @@ void reload_early_microcode(void)
 		break;
 	case X86_VENDOR_AMD:
 		if (family >= 0x10)
-			reload_ucode_amd();
+			reload_ucode_amd(cpu);
 		break;
 	default:
 		break;
 	}
 }
 
-static void collect_cpu_info_local(void *arg)
-{
-	struct cpu_info_ctx *ctx = arg;
+/* fake device for request_firmware */
+static struct platform_device	*microcode_pdev;
 
-	ctx->err = microcode_ops->collect_cpu_info(smp_processor_id(),
-						   ctx->cpu_sig);
-}
+#ifdef CONFIG_MICROCODE_LATE_LOADING
+/*
+ * Late loading dance. Why the heavy-handed stomp_machine effort?
+ *
+ * - HT siblings must be idle and not execute other code while the other sibling
+ *   is loading microcode in order to avoid any negative interactions caused by
+ *   the loading.
+ *
+ * - In addition, microcode update on the cores must be serialized until this
+ *   requirement can be relaxed in the future. Right now, this is conservative
+ *   and good.
+ */
+enum sibling_ctrl {
+	/* Spinwait with timeout */
+	SCTRL_WAIT,
+	/* Invoke the microcode_apply() callback */
+	SCTRL_APPLY,
+	/* Proceed without invoking the microcode_apply() callback */
+	SCTRL_DONE,
+};
+
+struct microcode_ctrl {
+	enum sibling_ctrl	ctrl;
+	enum ucode_state	result;
+	unsigned int		ctrl_cpu;
+	bool			nmi_enabled;
+};
+
+DEFINE_STATIC_KEY_FALSE(microcode_nmi_handler_enable);
+static DEFINE_PER_CPU(struct microcode_ctrl, ucode_ctrl);
+static atomic_t late_cpus_in, offline_in_nmi;
+static unsigned int loops_per_usec;
+static cpumask_t cpu_offline_mask;
 
-static int collect_cpu_info_on_target(int cpu, struct cpu_signature *cpu_sig)
+static noinstr bool wait_for_cpus(atomic_t *cnt)
 {
-	struct cpu_info_ctx ctx = { .cpu_sig = cpu_sig, .err = 0 };
-	int ret;
+	unsigned int timeout, loops;
 
-	ret = smp_call_function_single(cpu, collect_cpu_info_local, &ctx, 1);
-	if (!ret)
-		ret = ctx.err;
+	WARN_ON_ONCE(raw_atomic_dec_return(cnt) < 0);
 
-	return ret;
+	for (timeout = 0; timeout < USEC_PER_SEC; timeout++) {
+		if (!raw_atomic_read(cnt))
+			return true;
+
+		for (loops = 0; loops < loops_per_usec; loops++)
+			cpu_relax();
+
+		/* If invoked directly, tickle the NMI watchdog */
+		if (!microcode_ops->use_nmi && !(timeout % USEC_PER_MSEC)) {
+			instrumentation_begin();
+			touch_nmi_watchdog();
+			instrumentation_end();
+		}
+	}
+	/* Prevent the late comers from making progress and let them time out */
+	raw_atomic_inc(cnt);
+	return false;
 }
 
-static int collect_cpu_info(int cpu)
+static noinstr bool wait_for_ctrl(void)
 {
-	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
-	int ret;
+	unsigned int timeout, loops;
 
-	memset(uci, 0, sizeof(*uci));
+	for (timeout = 0; timeout < USEC_PER_SEC; timeout++) {
+		if (raw_cpu_read(ucode_ctrl.ctrl) != SCTRL_WAIT)
+			return true;
 
-	ret = collect_cpu_info_on_target(cpu, &uci->cpu_sig);
-	if (!ret)
-		uci->valid = 1;
+		for (loops = 0; loops < loops_per_usec; loops++)
+			cpu_relax();
 
-	return ret;
+		/* If invoked directly, tickle the NMI watchdog */
+		if (!microcode_ops->use_nmi && !(timeout % USEC_PER_MSEC)) {
+			instrumentation_begin();
+			touch_nmi_watchdog();
+			instrumentation_end();
+		}
+	}
+	return false;
 }
 
-static void apply_microcode_local(void *arg)
+/*
+ * Protected against instrumentation up to the point where the primary
+ * thread completed the update. See microcode_nmi_handler() for details.
+ */
+static noinstr bool load_secondary_wait(unsigned int ctrl_cpu)
 {
-	enum ucode_state *err = arg;
+	/* Initial rendezvous to ensure that all CPUs have arrived */
+	if (!wait_for_cpus(&late_cpus_in)) {
+		raw_cpu_write(ucode_ctrl.result, UCODE_TIMEOUT);
+		return false;
+	}
 
-	*err = microcode_ops->apply_microcode(smp_processor_id());
+	/*
+	 * Wait for primary threads to complete. If one of them hangs due
+	 * to the update, there is no way out. This is non-recoverable
+	 * because the CPU might hold locks or resources and confuse the
+	 * scheduler, watchdogs etc. There is no way to safely evacuate the
+	 * machine.
+	 */
+	if (wait_for_ctrl())
+		return true;
+
+	instrumentation_begin();
+	panic("Microcode load: Primary CPU %d timed out\n", ctrl_cpu);
+	instrumentation_end();
 }
 
-static int apply_microcode_on_target(int cpu)
+/*
+ * Protected against instrumentation up to the point where the primary
+ * thread completed the update. See microcode_nmi_handler() for details.
+ */
+static noinstr void load_secondary(unsigned int cpu)
 {
-	enum ucode_state err;
-	int ret;
-
-	ret = smp_call_function_single(cpu, apply_microcode_local, &err, 1);
-	if (!ret) {
-		if (err == UCODE_ERROR)
-			ret = 1;
+	unsigned int ctrl_cpu = raw_cpu_read(ucode_ctrl.ctrl_cpu);
+	enum ucode_state ret;
+
+	if (!load_secondary_wait(ctrl_cpu)) {
+		instrumentation_begin();
+		pr_err_once("load: %d CPUs timed out\n",
+			    atomic_read(&late_cpus_in) - 1);
+		instrumentation_end();
+		return;
 	}
-	return ret;
-}
 
-/* fake device for request_firmware */
-static struct platform_device	*microcode_pdev;
+	/* Primary thread completed. Allow to invoke instrumentable code */
+	instrumentation_begin();
+	/*
+	 * If the primary succeeded then invoke the apply() callback,
+	 * otherwise copy the state from the primary thread.
+	 */
+	if (this_cpu_read(ucode_ctrl.ctrl) == SCTRL_APPLY)
+		ret = microcode_ops->apply_microcode(cpu);
+	else
+		ret = per_cpu(ucode_ctrl.result, ctrl_cpu);
 
-#ifdef CONFIG_MICROCODE_LATE_LOADING
-/*
- * Late loading dance. Why the heavy-handed stomp_machine effort?
- *
- * - HT siblings must be idle and not execute other code while the other sibling
- *   is loading microcode in order to avoid any negative interactions caused by
- *   the loading.
- *
- * - In addition, microcode update on the cores must be serialized until this
- *   requirement can be relaxed in the future. Right now, this is conservative
- *   and good.
- */
-#define SPINUNIT 100 /* 100 nsec */
+	this_cpu_write(ucode_ctrl.result, ret);
+	this_cpu_write(ucode_ctrl.ctrl, SCTRL_DONE);
+	instrumentation_end();
+}
 
-static int check_online_cpus(void)
+static void __load_primary(unsigned int cpu)
 {
-	unsigned int cpu;
+	struct cpumask *secondaries = topology_sibling_cpumask(cpu);
+	enum sibling_ctrl ctrl;
+	enum ucode_state ret;
+	unsigned int sibling;
+
+	/* Initial rendezvous to ensure that all CPUs have arrived */
+	if (!wait_for_cpus(&late_cpus_in)) {
+		this_cpu_write(ucode_ctrl.result, UCODE_TIMEOUT);
+		pr_err_once("load: %d CPUs timed out\n", atomic_read(&late_cpus_in) - 1);
+		return;
+	}
+
+	ret = microcode_ops->apply_microcode(cpu);
+	this_cpu_write(ucode_ctrl.result, ret);
+	this_cpu_write(ucode_ctrl.ctrl, SCTRL_DONE);
 
 	/*
-	 * Make sure all CPUs are online.  It's fine for SMT to be disabled if
-	 * all the primary threads are still online.
+	 * If the update was successful, let the siblings run the apply()
+	 * callback. If not, tell them it's done. This also covers the
+	 * case where the CPU has uniform loading at package or system
+	 * scope implemented but does not advertise it.
 	 */
-	for_each_present_cpu(cpu) {
-		if (topology_is_primary_thread(cpu) && !cpu_online(cpu)) {
-			pr_err("Not all CPUs online, aborting microcode update.\n");
-			return -EINVAL;
-		}
+	if (ret == UCODE_UPDATED || ret == UCODE_OK)
+		ctrl = SCTRL_APPLY;
+	else
+		ctrl = SCTRL_DONE;
+
+	for_each_cpu(sibling, secondaries) {
+		if (sibling != cpu)
+			per_cpu(ucode_ctrl.ctrl, sibling) = ctrl;
+	}
+}
+
+static bool kick_offline_cpus(unsigned int nr_offl)
+{
+	unsigned int cpu, timeout;
+
+	for_each_cpu(cpu, &cpu_offline_mask) {
+		/* Enable the rendezvous handler and send NMI */
+		per_cpu(ucode_ctrl.nmi_enabled, cpu) = true;
+		apic_send_nmi_to_offline_cpu(cpu);
 	}
 
-	return 0;
+	/* Wait for them to arrive */
+	for (timeout = 0; timeout < (USEC_PER_SEC / 2); timeout++) {
+		if (atomic_read(&offline_in_nmi) == nr_offl)
+			return true;
+		udelay(1);
+	}
+	/* Let the others time out */
+	return false;
 }
 
-static atomic_t late_cpus_in;
-static atomic_t late_cpus_out;
+static void release_offline_cpus(void)
+{
+	unsigned int cpu;
+
+	for_each_cpu(cpu, &cpu_offline_mask)
+		per_cpu(ucode_ctrl.ctrl, cpu) = SCTRL_DONE;
+}
 
-static int __wait_for_cpus(atomic_t *t, long long timeout)
+static void load_primary(unsigned int cpu)
 {
-	int all_cpus = num_online_cpus();
+	unsigned int nr_offl = cpumask_weight(&cpu_offline_mask);
+	bool proceed = true;
 
-	atomic_inc(t);
+	/* Kick soft-offlined SMT siblings if required */
+	if (!cpu && nr_offl)
+		proceed = kick_offline_cpus(nr_offl);
 
-	while (atomic_read(t) < all_cpus) {
-		if (timeout < SPINUNIT) {
-			pr_err("Timeout while waiting for CPUs rendezvous, remaining: %d\n",
-				all_cpus - atomic_read(t));
-			return 1;
-		}
+	/* If the soft-offlined CPUs did not respond, abort */
+	if (proceed)
+		__load_primary(cpu);
 
-		ndelay(SPINUNIT);
-		timeout -= SPINUNIT;
+	/* Unconditionally release soft-offlined SMT siblings if required */
+	if (!cpu && nr_offl)
+		release_offline_cpus();
+}
 
-		touch_nmi_watchdog();
+/*
+ * Minimal stub rendezvous handler for soft-offlined CPUs which participate
+ * in the NMI rendezvous to protect against a concurrent NMI on affected
+ * CPUs.
+ */
+void noinstr microcode_offline_nmi_handler(void)
+{
+	if (!raw_cpu_read(ucode_ctrl.nmi_enabled))
+		return;
+	raw_cpu_write(ucode_ctrl.nmi_enabled, false);
+	raw_cpu_write(ucode_ctrl.result, UCODE_OFFLINE);
+	raw_atomic_inc(&offline_in_nmi);
+	wait_for_ctrl();
+}
+
+static noinstr bool microcode_update_handler(void)
+{
+	unsigned int cpu = raw_smp_processor_id();
+
+	if (raw_cpu_read(ucode_ctrl.ctrl_cpu) == cpu) {
+		instrumentation_begin();
+		load_primary(cpu);
+		instrumentation_end();
+	} else {
+		load_secondary(cpu);
 	}
-	return 0;
+
+	instrumentation_begin();
+	touch_nmi_watchdog();
+	instrumentation_end();
+
+	return true;
 }
 
 /*
- * Returns:
- * < 0 - on error
- *   0 - success (no update done or microcode was updated)
+ * Protection against instrumentation is required for CPUs which are not
+ * safe against an NMI which is delivered to the secondary SMT sibling
+ * while the primary thread updates the microcode. Instrumentation can end
+ * up in #INT3, #DB and #PF. The IRET from those exceptions reenables NMI
+ * which is the opposite of what the NMI rendezvous is trying to achieve.
+ *
+ * The primary thread is safe versus instrumentation as the actual
+ * microcode update handles this correctly. It's only the sibling code
+ * path which must be NMI safe until the primary thread completed the
+ * update.
  */
-static int __reload_late(void *info)
+bool noinstr microcode_nmi_handler(void)
 {
-	int cpu = smp_processor_id();
-	enum ucode_state err;
-	int ret = 0;
+	if (!raw_cpu_read(ucode_ctrl.nmi_enabled))
+		return false;
 
-	/*
-	 * Wait for all CPUs to arrive. A load will not be attempted unless all
-	 * CPUs show up.
-	 * */
-	if (__wait_for_cpus(&late_cpus_in, NSEC_PER_SEC))
-		return -1;
+	raw_cpu_write(ucode_ctrl.nmi_enabled, false);
+	return microcode_update_handler();
+}
+
+static int load_cpus_stopped(void *unused)
+{
+	if (microcode_ops->use_nmi) {
+		/* Enable the NMI handler and raise NMI */
+		this_cpu_write(ucode_ctrl.nmi_enabled, true);
+		apic->send_IPI(smp_processor_id(), NMI_VECTOR);
+	} else {
+		/* Just invoke the handler directly */
+		microcode_update_handler();
+	}
+	return 0;
+}
+
+static int load_late_stop_cpus(bool is_safe)
+{
+	unsigned int cpu, updated = 0, failed = 0, timedout = 0, siblings = 0;
+	unsigned int nr_offl, offline = 0;
+	int old_rev = boot_cpu_data.microcode;
+	struct cpuinfo_x86 prev_info;
+
+	if (!is_safe) {
+		pr_err("Late microcode loading without minimal revision check.\n");
+		pr_err("You should switch to early loading, if possible.\n");
+	}
+
+	atomic_set(&late_cpus_in, num_online_cpus());
+	atomic_set(&offline_in_nmi, 0);
+	loops_per_usec = loops_per_jiffy / (TICK_NSEC / 1000);
 
 	/*
-	 * On an SMT system, it suffices to load the microcode on one sibling of
-	 * the core because the microcode engine is shared between the threads.
-	 * Synchronization still needs to take place so that no concurrent
-	 * loading attempts happen on multiple threads of an SMT core. See
-	 * below.
+	 * Take a snapshot before the microcode update in order to compare and
+	 * check whether any bits changed after an update.
 	 */
-	if (cpumask_first(topology_sibling_cpumask(cpu)) == cpu)
-		apply_microcode_local(&err);
-	else
-		goto wait_for_siblings;
+	store_cpu_caps(&prev_info);
+
+	if (microcode_ops->use_nmi)
+		static_branch_enable_cpuslocked(&microcode_nmi_handler_enable);
 
-	if (err >= UCODE_NFOUND) {
-		if (err == UCODE_ERROR)
-			pr_warn("Error reloading microcode on CPU %d\n", cpu);
+	stop_machine_cpuslocked(load_cpus_stopped, NULL, cpu_online_mask);
 
-		ret = -1;
+	if (microcode_ops->use_nmi)
+		static_branch_disable_cpuslocked(&microcode_nmi_handler_enable);
+
+	/* 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;
+		case UCODE_OFFLINE:	offline++; break;
+		default:		failed++; break;
+		}
 	}
 
-wait_for_siblings:
-	if (__wait_for_cpus(&late_cpus_out, NSEC_PER_SEC))
-		panic("Timeout during microcode update!\n");
+	if (microcode_ops->finalize_late_load)
+		microcode_ops->finalize_late_load(!updated);
 
-	/*
-	 * At least one thread has completed update on each core.
-	 * For others, simply call the update to make sure the
-	 * per-cpu cpuinfo can be updated with right microcode
-	 * revision.
-	 */
-	if (cpumask_first(topology_sibling_cpumask(cpu)) != cpu)
-		apply_microcode_local(&err);
+	if (!updated) {
+		/* Nothing changed. */
+		if (!failed && !timedout)
+			return 0;
 
-	return ret;
+		nr_offl = cpumask_weight(&cpu_offline_mask);
+		if (offline < nr_offl) {
+			pr_warn("%u offline siblings did not respond.\n",
+				nr_offl - atomic_read(&offline_in_nmi));
+			return -EIO;
+		}
+		pr_err("update failed: %u CPUs failed %u CPUs timed out\n",
+		       failed, timedout);
+		return -EIO;
+	}
+
+	if (!is_safe || failed || timedout)
+		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;
 }
 
 /*
- * Reload microcode late on all CPUs. Wait for a sec until they
- * all gather together.
+ * 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.
+ *
+ *    If the microcode load is not safe against NMI then all SMT threads
+ *    must be online as well because they still react to NMIs when they are
+ *    soft-offlined and parked in one of the play_dead() variants. So if a
+ *    NMI hits while the primary thread updates the microcode the resulting
+ *    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.
+ *
+ *    As soft-offlined CPUs still react on NMIs, the SMT sibling
+ *    restriction can be lifted when the vendor driver signals to use NMI
+ *    for rendezvous and the APIC provides a mechanism to send an NMI to a
+ *    soft-offlined CPU. The soft-offlined CPUs are then able to
+ *    participate in the rendezvous in a trivial stub handler.
+ *
+ * 2) Initialize the per CPU control structure and create a cpumask
+ *    which contains "offline"; secondary threads, so they can be handled
+ *    correctly by a control CPU.
  */
-static int microcode_reload_late(void)
+static bool setup_cpus(void)
 {
-	int ret;
+	struct microcode_ctrl ctrl = { .ctrl = SCTRL_WAIT, .result = -1, };
+	bool allow_smt_offline;
+	unsigned int cpu;
 
-	pr_err("Attempting late microcode loading - it is dangerous and taints the kernel.\n");
-	pr_err("You should switch to early loading, if possible.\n");
+	allow_smt_offline = microcode_ops->nmi_safe ||
+		(microcode_ops->use_nmi && apic->nmi_to_offline_cpu);
 
-	atomic_set(&late_cpus_in,  0);
-	atomic_set(&late_cpus_out, 0);
+	cpumask_clear(&cpu_offline_mask);
 
-	ret = stop_machine_cpuslocked(__reload_late, NULL, cpu_online_mask);
-	if (ret == 0)
-		microcode_check();
+	for_each_cpu_and(cpu, cpu_present_mask, &cpus_booted_once_mask) {
+		/*
+		 * Offline CPUs sit in one of the play_dead() functions
+		 * with interrupts disabled, but they still react on NMIs
+		 * and execute arbitrary code. Also MWAIT being updated
+		 * while the offline CPU sits there is not necessarily safe
+		 * on all CPU variants.
+		 *
+		 * Mark them in the offline_cpus mask which will be handled
+		 * by CPU0 later in the update process.
+		 *
+		 * Ensure that the primary thread is online so that it is
+		 * guaranteed that all cores are updated.
+		 */
+		if (!cpu_online(cpu)) {
+			if (topology_is_primary_thread(cpu) || !allow_smt_offline) {
+				pr_err("CPU %u not online, loading aborted\n", cpu);
+				return false;
+			}
+			cpumask_set_cpu(cpu, &cpu_offline_mask);
+			per_cpu(ucode_ctrl, cpu) = ctrl;
+			continue;
+		}
 
-	pr_info("Reload completed, microcode revision: 0x%x\n", boot_cpu_data.microcode);
+		/*
+		 * Initialize the per CPU state. This is core scope for now,
+		 * but prepared to take package or system scope into account.
+		 */
+		ctrl.ctrl_cpu = cpumask_first(topology_sibling_cpumask(cpu));
+		per_cpu(ucode_ctrl, cpu) = ctrl;
+	}
+	return true;
+}
 
-	return ret;
+static int load_late_locked(void)
+{
+	if (!setup_cpus())
+		return -EBUSY;
+
+	switch (microcode_ops->request_microcode_fw(0, &microcode_pdev->dev)) {
+	case UCODE_NEW:
+		return load_late_stop_cpus(false);
+	case UCODE_NEW_SAFE:
+		return load_late_stop_cpus(true);
+	case UCODE_NFOUND:
+		return -ENOENT;
+	default:
+		return -EBADFD;
+	}
 }
 
 static ssize_t reload_store(struct device *dev,
 			    struct device_attribute *attr,
 			    const char *buf, size_t size)
 {
-	enum ucode_state tmp_ret = UCODE_OK;
-	int bsp = boot_cpu_data.cpu_index;
 	unsigned long val;
-	ssize_t ret = 0;
+	ssize_t ret;
 
 	ret = kstrtoul(buf, 0, &val);
-	if (ret)
-		return ret;
-
-	if (val != 1)
-		return size;
+	if (ret || val != 1)
+		return -EINVAL;
 
 	cpus_read_lock();
-
-	ret = check_online_cpus();
-	if (ret)
-		goto put;
-
-	tmp_ret = microcode_ops->request_microcode_fw(bsp, &microcode_pdev->dev, true);
-	if (tmp_ret != UCODE_NEW)
-		goto put;
-
-	mutex_lock(&microcode_mutex);
-	ret = microcode_reload_late();
-	mutex_unlock(&microcode_mutex);
-
-put:
+	ret = load_late_locked();
 	cpus_read_unlock();
 
-	if (ret == 0)
-		ret = size;
-
-	add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);
-
-	return ret;
+	return ret ? : size;
 }
 
 static DEVICE_ATTR_WO(reload);
@@ -560,7 +725,7 @@ static ssize_t version_show(struct device *dev,
 	return sprintf(buf, "0x%x\n", uci->cpu_sig.rev);
 }
 
-static ssize_t pf_show(struct device *dev,
+static ssize_t processor_flags_show(struct device *dev,
 			struct device_attribute *attr, char *buf)
 {
 	struct ucode_cpu_info *uci = ucode_cpu_info + dev->id;
@@ -568,8 +733,8 @@ static ssize_t pf_show(struct device *dev,
 	return sprintf(buf, "0x%x\n", uci->cpu_sig.pf);
 }
 
-static DEVICE_ATTR(version, 0444, version_show, NULL);
-static DEVICE_ATTR(processor_flags, 0444, pf_show, NULL);
+static DEVICE_ATTR_RO(version);
+static DEVICE_ATTR_RO(processor_flags);
 
 static struct attribute *mc_default_attrs[] = {
 	&dev_attr_version.attr,
@@ -588,91 +753,6 @@ static void microcode_fini_cpu(int cpu)
 		microcode_ops->microcode_fini_cpu(cpu);
 }
 
-static enum ucode_state microcode_resume_cpu(int cpu)
-{
-	if (apply_microcode_on_target(cpu))
-		return UCODE_ERROR;
-
-	pr_debug("CPU%d updated upon resume\n", cpu);
-
-	return UCODE_OK;
-}
-
-static enum ucode_state microcode_init_cpu(int cpu, bool refresh_fw)
-{
-	enum ucode_state ustate;
-	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
-
-	if (uci->valid)
-		return UCODE_OK;
-
-	if (collect_cpu_info(cpu))
-		return UCODE_ERROR;
-
-	/* --dimm. Trigger a delayed update? */
-	if (system_state != SYSTEM_RUNNING)
-		return UCODE_NFOUND;
-
-	ustate = microcode_ops->request_microcode_fw(cpu, &microcode_pdev->dev, refresh_fw);
-	if (ustate == UCODE_NEW) {
-		pr_debug("CPU%d updated upon init\n", cpu);
-		apply_microcode_on_target(cpu);
-	}
-
-	return ustate;
-}
-
-static enum ucode_state microcode_update_cpu(int cpu)
-{
-	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
-
-	/* Refresh CPU microcode revision after resume. */
-	collect_cpu_info(cpu);
-
-	if (uci->valid)
-		return microcode_resume_cpu(cpu);
-
-	return microcode_init_cpu(cpu, false);
-}
-
-static int mc_device_add(struct device *dev, struct subsys_interface *sif)
-{
-	int err, cpu = dev->id;
-
-	if (!cpu_online(cpu))
-		return 0;
-
-	pr_debug("CPU%d added\n", cpu);
-
-	err = sysfs_create_group(&dev->kobj, &mc_attr_group);
-	if (err)
-		return err;
-
-	if (microcode_init_cpu(cpu, true) == UCODE_ERROR)
-		return -EINVAL;
-
-	return err;
-}
-
-static void mc_device_remove(struct device *dev, struct subsys_interface *sif)
-{
-	int cpu = dev->id;
-
-	if (!cpu_online(cpu))
-		return;
-
-	pr_debug("CPU%d removed\n", cpu);
-	microcode_fini_cpu(cpu);
-	sysfs_remove_group(&dev->kobj, &mc_attr_group);
-}
-
-static struct subsys_interface mc_cpu_interface = {
-	.name			= "microcode",
-	.subsys			= &cpu_subsys,
-	.add_dev		= mc_device_add,
-	.remove_dev		= mc_device_remove,
-};
-
 /**
  * microcode_bsp_resume - Update boot CPU microcode during resume.
  */
@@ -681,27 +761,28 @@ void microcode_bsp_resume(void)
 	int cpu = smp_processor_id();
 	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 
-	if (uci->valid && uci->mc)
+	if (uci->mc)
 		microcode_ops->apply_microcode(cpu);
-	else if (!uci->mc)
-		reload_early_microcode();
+	else
+		reload_early_microcode(cpu);
 }
 
 static struct syscore_ops mc_syscore_ops = {
-	.resume			= microcode_bsp_resume,
+	.resume	= microcode_bsp_resume,
 };
 
-static int mc_cpu_starting(unsigned int cpu)
-{
-	microcode_update_cpu(cpu);
-	pr_debug("CPU%d added\n", cpu);
-	return 0;
-}
-
 static int mc_cpu_online(unsigned int cpu)
 {
+	struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
 	struct device *dev = get_cpu_device(cpu);
 
+	memset(uci, 0, sizeof(*uci));
+
+	microcode_ops->collect_cpu_info(cpu, &uci->cpu_sig);
+	cpu_data(cpu).microcode = uci->cpu_sig.rev;
+	if (!cpu)
+		boot_cpu_data.microcode = uci->cpu_sig.rev;
+
 	if (sysfs_create_group(&dev->kobj, &mc_attr_group))
 		pr_err("Failed to create group for CPU%d\n", cpu);
 	return 0;
@@ -709,13 +790,10 @@ static int mc_cpu_online(unsigned int cpu)
 
 static int mc_cpu_down_prep(unsigned int cpu)
 {
-	struct device *dev;
+	struct device *dev = get_cpu_device(cpu);
 
-	dev = get_cpu_device(cpu);
-	/* Suspend is in progress, only remove the interface */
+	microcode_fini_cpu(cpu);
 	sysfs_remove_group(&dev->kobj, &mc_attr_group);
-	pr_debug("CPU%d removed\n", cpu);
-
 	return 0;
 }
 
@@ -733,6 +811,7 @@ static const struct attribute_group cpu_root_microcode_group = {
 
 static int __init microcode_init(void)
 {
+	struct device *dev_root;
 	struct cpuinfo_x86 *c = &boot_cpu_data;
 	int error;
 
@@ -749,51 +828,34 @@ static int __init microcode_init(void)
 	if (!microcode_ops)
 		return -ENODEV;
 
-	microcode_pdev = platform_device_register_simple("microcode", -1,
-							 NULL, 0);
-	if (IS_ERR(microcode_pdev))
-		return PTR_ERR(microcode_pdev);
-
-	cpus_read_lock();
-	mutex_lock(&microcode_mutex);
-	error = subsys_interface_register(&mc_cpu_interface);
-	mutex_unlock(&microcode_mutex);
-	cpus_read_unlock();
+	pr_info_once("Current revision: 0x%08x\n", (early_data.new_rev ?: early_data.old_rev));
 
-	if (error)
-		goto out_pdev;
+	if (early_data.new_rev)
+		pr_info_once("Updated early from: 0x%08x\n", early_data.old_rev);
 
-	error = sysfs_create_group(&cpu_subsys.dev_root->kobj,
-				   &cpu_root_microcode_group);
+	microcode_pdev = platform_device_register_simple("microcode", -1, NULL, 0);
+	if (IS_ERR(microcode_pdev))
+		return PTR_ERR(microcode_pdev);
 
-	if (error) {
-		pr_err("Error creating microcode group!\n");
-		goto out_driver;
+	dev_root = bus_get_dev_root(&cpu_subsys);
+	if (dev_root) {
+		error = sysfs_create_group(&dev_root->kobj, &cpu_root_microcode_group);
+		put_device(dev_root);
+		if (error) {
+			pr_err("Error creating microcode group!\n");
+			goto out_pdev;
+		}
 	}
 
 	register_syscore_ops(&mc_syscore_ops);
-	cpuhp_setup_state_nocalls(CPUHP_AP_MICROCODE_LOADER, "x86/microcode:starting",
-				  mc_cpu_starting, NULL);
-	cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "x86/microcode:online",
-				  mc_cpu_online, mc_cpu_down_prep);
-
-	pr_info("Microcode Update Driver: v%s.", DRIVER_VERSION);
+	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/microcode:online",
+			  mc_cpu_online, mc_cpu_down_prep);
 
 	return 0;
 
- out_driver:
-	cpus_read_lock();
-	mutex_lock(&microcode_mutex);
-
-	subsys_interface_unregister(&mc_cpu_interface);
-
-	mutex_unlock(&microcode_mutex);
-	cpus_read_unlock();
-
  out_pdev:
 	platform_device_unregister(microcode_pdev);
 	return error;
 
 }
-fs_initcall(save_microcode_in_initrd);
 late_initcall(microcode_init);