blob: 06db901fabe8e0e9d61403b754080fe2f9b46ac3 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0-or-later
* Intel SMP support routines.
* (c) 1995 Alan Cox, Building #3 <>
* (c) 1998-99, 2000, 2009 Ingo Molnar <>
* (c) 2002,2003 Andi Kleen, SuSE Labs.
* i386 and x86_64 integration by Glauber Costa <>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/spinlock.h>
#include <linux/export.h>
#include <linux/kernel_stat.h>
#include <linux/mc146818rtc.h>
#include <linux/cache.h>
#include <linux/interrupt.h>
#include <linux/cpu.h>
#include <linux/gfp.h>
#include <asm/mtrr.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
#include <asm/proto.h>
#include <asm/apic.h>
#include <asm/idtentry.h>
#include <asm/nmi.h>
#include <asm/mce.h>
#include <asm/trace/irq_vectors.h>
#include <asm/kexec.h>
#include <asm/virtext.h>
* Some notes on x86 processor bugs affecting SMP operation:
* Pentium, Pentium Pro, II, III (and all CPUs) have bugs.
* The Linux implications for SMP are handled as follows:
* Pentium III / [Xeon]
* None of the E1AP-E3AP errata are visible to the user.
* E1AP. see PII A1AP
* E2AP. see PII A2AP
* E3AP. see PII A3AP
* Pentium II / [Xeon]
* None of the A1AP-A3AP errata are visible to the user.
* A1AP. see PPro 1AP
* A2AP. see PPro 2AP
* A3AP. see PPro 7AP
* Pentium Pro
* None of 1AP-9AP errata are visible to the normal user,
* except occasional delivery of 'spurious interrupt' as trap #15.
* This is very rare and a non-problem.
* 1AP. Linux maps APIC as non-cacheable
* 2AP. worked around in hardware
* 3AP. fixed in C0 and above steppings microcode update.
* Linux does not use excessive STARTUP_IPIs.
* 4AP. worked around in hardware
* 5AP. symmetric IO mode (normal Linux operation) not affected.
* 'noapic' mode has vector 0xf filled out properly.
* 6AP. 'noapic' mode might be affected - fixed in later steppings
* 7AP. We do not assume writes to the LVT deasserting IRQs
* 8AP. We do not enable low power mode (deep sleep) during MP bootup
* 9AP. We do not use mixed mode
* Pentium
* There is a marginal case where REP MOVS on 100MHz SMP
* machines with B stepping processors can fail. XXX should provide
* an L1cache=Writethrough or L1cache=off option.
* B stepping CPUs may hang. There are hardware work arounds
* for this. We warn about it in case your board doesn't have the work
* arounds. Basically that's so I can tell anyone with a B stepping
* CPU and SMP problems "tough".
* Specific items [From Pentium Processor Specification Update]
* 1AP. Linux doesn't use remote read
* 2AP. Linux doesn't trust APIC errors
* 3AP. We work around this
* 4AP. Linux never generated 3 interrupts of the same priority
* to cause a lost local interrupt.
* 5AP. Remote read is never used
* 6AP. not affected - worked around in hardware
* 7AP. not affected - worked around in hardware
* 8AP. worked around in hardware - we get explicit CS errors if not
* 9AP. only 'noapic' mode affected. Might generate spurious
* interrupts, we log only the first one and count the
* rest silently.
* 10AP. not affected - worked around in hardware
* 11AP. Linux reads the APIC between writes to avoid this, as per
* the documentation. Make sure you preserve this as it affects
* the C stepping chips too.
* 12AP. not affected - worked around in hardware
* 13AP. not affected - worked around in hardware
* 14AP. we always deassert INIT during bootup
* 15AP. not affected - worked around in hardware
* 16AP. not affected - worked around in hardware
* 17AP. not affected - worked around in hardware
* 18AP. not affected - worked around in hardware
* 19AP. not affected - worked around in BIOS
* If this sounds worrying believe me these bugs are either ___RARE___,
* or are signal timing bugs worked around in hardware and there's
* about nothing of note with C stepping upwards.
static atomic_t stopping_cpu = ATOMIC_INIT(-1);
static bool smp_no_nmi_ipi = false;
static int smp_stop_nmi_callback(unsigned int val, struct pt_regs *regs)
/* We are registered on stopping cpu too, avoid spurious NMI */
if (raw_smp_processor_id() == atomic_read(&stopping_cpu))
* this function calls the 'stop' function on all other CPUs in the system.
static int register_stop_handler(void)
return register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback,
NMI_FLAG_FIRST, "smp_stop");
static void native_stop_other_cpus(int wait)
unsigned long flags;
unsigned long timeout;
if (reboot_force)
* Use an own vector here because smp_call_function
* does lots of things not suitable in a panic situation.
* We start by using the REBOOT_VECTOR irq.
* The irq is treated as a sync point to allow critical
* regions of code on other cpus to release their spin locks
* and re-enable irqs. Jumping straight to an NMI might
* accidentally cause deadlocks with further shutdown/panic
* code. By syncing, we give the cpus up to one second to
* finish their work before we force them off with the NMI.
if (num_online_cpus() > 1) {
/* did someone beat us here? */
if (atomic_cmpxchg(&stopping_cpu, -1, safe_smp_processor_id()) != -1)
/* sync above data before sending IRQ */
* Don't wait longer than a second for IPI completion. The
* wait request is not checked here because that would
* prevent an NMI shutdown attempt in case that not all
* CPUs reach shutdown state.
timeout = USEC_PER_SEC;
while (num_online_cpus() > 1 && timeout--)
/* if the REBOOT_VECTOR didn't work, try with the NMI */
if (num_online_cpus() > 1) {
* If NMI IPI is enabled, try to register the stop handler
* and send the IPI. In any case try to wait for the other
* CPUs to stop.
if (!smp_no_nmi_ipi && !register_stop_handler()) {
/* Sync above data before sending IRQ */
pr_emerg("Shutting down cpus with NMI\n");
* Don't wait longer than 10 ms if the caller didn't
* request it. If wait is true, the machine hangs here if
* one or more CPUs do not reach shutdown state.
timeout = USEC_PER_MSEC * 10;
while (num_online_cpus() > 1 && (wait || timeout--))
* Reschedule call back. KVM uses this interrupt to force a cpu out of
* guest mode.
static int __init nonmi_ipi_setup(char *str)
smp_no_nmi_ipi = true;
return 1;
__setup("nonmi_ipi", nonmi_ipi_setup);
struct smp_ops smp_ops = {
.smp_prepare_boot_cpu = native_smp_prepare_boot_cpu,
.smp_prepare_cpus = native_smp_prepare_cpus,
.smp_cpus_done = native_smp_cpus_done,
.stop_other_cpus = native_stop_other_cpus,
#if defined(CONFIG_KEXEC_CORE)
.crash_stop_other_cpus = kdump_nmi_shootdown_cpus,
.smp_send_reschedule = native_smp_send_reschedule,
.cpu_up = native_cpu_up,
.cpu_die = native_cpu_die,
.cpu_disable = native_cpu_disable,
.play_dead = native_play_dead,
.send_call_func_ipi = native_send_call_func_ipi,
.send_call_func_single_ipi = native_send_call_func_single_ipi,