diff options
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kernel/cpu/microcode/core.c | 111 |
1 files changed, 83 insertions, 28 deletions
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index 7b8ade552b55..6c90836de67f 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -272,54 +272,65 @@ struct microcode_ctrl { DEFINE_STATIC_KEY_FALSE(microcode_nmi_handler_enable); static DEFINE_PER_CPU(struct microcode_ctrl, ucode_ctrl); +static unsigned int loops_per_usec; static atomic_t late_cpus_in; -static bool wait_for_cpus(atomic_t *cnt) +static noinstr bool wait_for_cpus(atomic_t *cnt) { - unsigned int timeout; + unsigned int timeout, loops; - WARN_ON_ONCE(atomic_dec_return(cnt) < 0); + WARN_ON_ONCE(raw_atomic_dec_return(cnt) < 0); for (timeout = 0; timeout < USEC_PER_SEC; timeout++) { - if (!atomic_read(cnt)) + if (!raw_atomic_read(cnt)) return true; - udelay(1); + 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)) + 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 */ - atomic_inc(cnt); + raw_atomic_inc(cnt); return false; } -static bool wait_for_ctrl(void) +static noinstr bool wait_for_ctrl(void) { - unsigned int timeout; + unsigned int timeout, loops; for (timeout = 0; timeout < USEC_PER_SEC; timeout++) { - if (this_cpu_read(ucode_ctrl.ctrl) != SCTRL_WAIT) + if (raw_cpu_read(ucode_ctrl.ctrl) != SCTRL_WAIT) return true; - udelay(1); + + for (loops = 0; loops < loops_per_usec; loops++) + cpu_relax(); + /* If invoked directly, tickle the NMI watchdog */ - if (!microcode_ops->use_nmi && !(timeout % 1000)) + if (!microcode_ops->use_nmi && !(timeout % USEC_PER_MSEC)) { + instrumentation_begin(); touch_nmi_watchdog(); + instrumentation_end(); + } } return false; } -static void load_secondary(unsigned int cpu) +/* + * 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) { - unsigned int ctrl_cpu = this_cpu_read(ucode_ctrl.ctrl_cpu); - enum ucode_state ret; - /* Initial rendezvous to ensure that all CPUs have arrived */ if (!wait_for_cpus(&late_cpus_in)) { - pr_err_once("load: %d CPUs timed out\n", atomic_read(&late_cpus_in) - 1); - this_cpu_write(ucode_ctrl.result, UCODE_TIMEOUT); - return; + raw_cpu_write(ucode_ctrl.result, UCODE_TIMEOUT); + return false; } /* @@ -329,9 +340,33 @@ static void load_secondary(unsigned int cpu) * scheduler, watchdogs etc. There is no way to safely evacuate the * machine. */ - if (!wait_for_ctrl()) - panic("Microcode load: Primary CPU %d timed out\n", ctrl_cpu); + if (wait_for_ctrl()) + return true; + + instrumentation_begin(); + panic("Microcode load: Primary CPU %d timed out\n", ctrl_cpu); + instrumentation_end(); +} +/* + * 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) +{ + 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; + } + + /* 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. @@ -343,6 +378,7 @@ static void load_secondary(unsigned int cpu) this_cpu_write(ucode_ctrl.result, ret); this_cpu_write(ucode_ctrl.ctrl, SCTRL_DONE); + instrumentation_end(); } static void load_primary(unsigned int cpu) @@ -380,25 +416,43 @@ static void load_primary(unsigned int cpu) } } -static bool microcode_update_handler(void) +static noinstr bool microcode_update_handler(void) { - unsigned int cpu = smp_processor_id(); + unsigned int cpu = raw_smp_processor_id(); - if (this_cpu_read(ucode_ctrl.ctrl_cpu) == cpu) + if (raw_cpu_read(ucode_ctrl.ctrl_cpu) == cpu) { + instrumentation_begin(); load_primary(cpu); - else + instrumentation_end(); + } else { load_secondary(cpu); + } + instrumentation_begin(); touch_nmi_watchdog(); + instrumentation_end(); + return true; } -bool microcode_nmi_handler(void) +/* + * 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. + */ +bool noinstr microcode_nmi_handler(void) { - if (!this_cpu_read(ucode_ctrl.nmi_enabled)) + if (!raw_cpu_read(ucode_ctrl.nmi_enabled)) return false; - this_cpu_write(ucode_ctrl.nmi_enabled, false); + raw_cpu_write(ucode_ctrl.nmi_enabled, false); return microcode_update_handler(); } @@ -425,6 +479,7 @@ static int load_late_stop_cpus(void) pr_err("You should switch to early loading, if possible.\n"); atomic_set(&late_cpus_in, num_online_cpus()); + loops_per_usec = loops_per_jiffy / (TICK_NSEC / 1000); /* * Take a snapshot before the microcode update in order to compare and |