diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 011cb7f200d9..db7512008ff7 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1320,7 +1320,7 @@ config MICROCODE_INITRD32 config MICROCODE_LATE_LOADING bool "Late microcode loading (DANGEROUS)" default n - depends on MICROCODE + depends on MICROCODE && SMP help Loading microcode late, when the system is up and executing instructions is a tricky business and should be avoided if possible. Just the sequence diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c index 99aa5a88d668..102aebcdb766 100644 --- a/arch/x86/kernel/cpu/microcode/amd.c +++ b/arch/x86/kernel/cpu/microcode/amd.c @@ -917,10 +917,11 @@ static void microcode_fini_cpu_amd(int cpu) } static struct microcode_ops microcode_amd_ops = { - .request_microcode_fw = request_microcode_amd, - .collect_cpu_info = collect_cpu_info_amd, - .apply_microcode = apply_microcode_amd, - .microcode_fini_cpu = microcode_fini_cpu_amd, + .request_microcode_fw = request_microcode_amd, + .collect_cpu_info = collect_cpu_info_amd, + .apply_microcode = apply_microcode_amd, + .microcode_fini_cpu = microcode_fini_cpu_amd, + .nmi_safe = true, }; struct microcode_ops * __init init_amd_microcode(void) diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index e306feeb374f..7af1b60527ec 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -254,23 +254,6 @@ static struct platform_device *microcode_pdev; */ #define SPINUNIT 100 /* 100 nsec */ -static int check_online_cpus(void) -{ - unsigned int cpu; - - /* - * Make sure all CPUs are online. It's fine for SMT to be disabled if - * all the primary threads are still online. - */ - 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; - } - } - - return 0; -} static atomic_t late_cpus_in; static atomic_t late_cpus_out; @@ -387,6 +370,35 @@ static int microcode_reload_late(void) return ret; } +/* + * 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. + */ +static bool ensure_cpus_are_online(void) +{ + unsigned int cpu; + + for_each_cpu_and(cpu, cpu_present_mask, &cpus_booted_once_mask) { + if (!cpu_online(cpu)) { + if (topology_is_primary_thread(cpu) || !microcode_ops->nmi_safe) { + pr_err("CPU %u not online\n", cpu); + return false; + } + } + } + return true; +} + static ssize_t reload_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t size) @@ -402,9 +414,10 @@ static ssize_t reload_store(struct device *dev, cpus_read_lock(); - ret = check_online_cpus(); - if (ret) + if (!ensure_cpus_are_online()) { + ret = -EBUSY; goto put; + } tmp_ret = microcode_ops->request_microcode_fw(bsp, µcode_pdev->dev); if (tmp_ret != UCODE_NEW) diff --git a/arch/x86/kernel/cpu/microcode/internal.h b/arch/x86/kernel/cpu/microcode/internal.h index 4bef216f8d6c..07aa5f8be69b 100644 --- a/arch/x86/kernel/cpu/microcode/internal.h +++ b/arch/x86/kernel/cpu/microcode/internal.h @@ -20,18 +20,17 @@ enum ucode_state { struct microcode_ops { enum ucode_state (*request_microcode_fw)(int cpu, struct device *dev); - void (*microcode_fini_cpu)(int cpu); /* - * The generic 'microcode_core' part guarantees that - * the callbacks below run on a target cpu when they - * are being called. + * The generic 'microcode_core' part guarantees that the callbacks + * below run on a target CPU when they are being called. * See also the "Synchronization" section in microcode_core.c. */ - enum ucode_state (*apply_microcode)(int cpu); - int (*collect_cpu_info)(int cpu, struct cpu_signature *csig); - void (*finalize_late_load)(int result); + enum ucode_state (*apply_microcode)(int cpu); + int (*collect_cpu_info)(int cpu, struct cpu_signature *csig); + void (*finalize_late_load)(int result); + unsigned int nmi_safe : 1; }; extern struct ucode_cpu_info ucode_cpu_info[];