// SPDX-License-Identifier: GPL-2.0-or-later
/*
* SMP support for pSeries machines.
*
* Dave Engebretsen, Peter Bergner, and
* Mike Corrigan {engebret|bergner|mikec}@us.ibm.com
*
* Plus various changes from other IBM teams...
*/
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/cache.h>
#include <linux/err.h>
#include <linux/device.h>
#include <linux/cpu.h>
#include <linux/pgtable.h>
#include <asm/ptrace.h>
#include <linux/atomic.h>
#include <asm/irq.h>
#include <asm/page.h>
#include <asm/io.h>
#include <asm/smp.h>
#include <asm/paca.h>
#include <asm/machdep.h>
#include <asm/cputable.h>
#include <asm/firmware.h>
#include <asm/rtas.h>
#include <asm/vdso_datapage.h>
#include <asm/cputhreads.h>
#include <asm/xics.h>
#include <asm/xive.h>
#include <asm/dbell.h>
#include <asm/plpar_wrappers.h>
#include <asm/code-patching.h>
#include <asm/svm.h>
#include <asm/kvm_guest.h>
#include "pseries.h"
/*
* The Primary thread of each non-boot processor was started from the OF client
* interface by prom_hold_cpus and is spinning on secondary_hold_spinloop.
*/
static cpumask_var_t of_spin_mask;
/* Query where a cpu is now. Return codes #defined in plpar_wrappers.h */
int smp_query_cpu_stopped(unsigned int pcpu)
{
int cpu_status, status;
int qcss_tok = rtas_function_token(RTAS_FN_QUERY_CPU_STOPPED_STATE);
if (qcss_tok == RTAS_UNKNOWN_SERVICE) {
printk_once(KERN_INFO
"Firmware doesn't support query-cpu-stopped-state\n");
return QCSS_HARDWARE_ERROR;
}
status = rtas_call(qcss_tok, 1, 2, &cpu_status, pcpu);
if (status != 0) {
printk(KERN_ERR
"RTAS query-cpu-stopped-state failed: %i\n", status);
return status;
}
return cpu_status;
}
/**
* smp_startup_cpu() - start the given cpu
*
* At boot time, there is nothing to do for primary threads which were
* started from Open Firmware. For anything else, call RTAS with the
* appropriate start location.
*
* Returns:
* 0 - failure
* 1 - success
*/
static inline int smp_startup_cpu(unsigned int lcpu)
{
int status;
unsigned long start_here =
__pa(ppc_function_entry(generic_secondary_smp_init));
unsigned int pcpu;
int start_cpu;
if (cpumask_test_cpu(lcpu, of_spin_mask))
/* Already started by OF and sitting in spin loop */
return 1;
pcpu = get_hard_smp_processor_id(lcpu);
/* Check to see if the CPU out of FW already for kexec */
if (smp_query_cpu_stopped(pcpu) == QCSS_NOT_STOPPED){
cpumask_set_cpu(lcpu, of_spin_mask);
return 1;
}
/*
* If the RTAS start-cpu token does not exist then presume the
* cpu is already spinning.
*/
start_cpu = rtas_function_token(RTAS_FN_START_CPU);
if (start_cpu == RTAS_UNKNOWN_SERVICE)
return 1;
status = rtas_call(start_cpu, 3, 1, NULL, pcpu, start_here, pcpu);
if (status != 0) {
printk(KERN_ERR "start-cpu failed: %i\n", status);
return 0;
}
return 1;
}
static void smp_setup_cpu(int cpu)
{
if (xive_enabled())
xive_smp_setup_cpu();
else if (cpu != boot_cpuid)
xics_setup_cpu();
if (firmware_has_feature(FW_FEATURE_SPLPAR))
vpa_init(cpu);
cpumask_clear_cpu(cpu, of_spin_mask);
}
static int smp_pSeries_kick_cpu(int nr)
{
if (nr < 0 || nr >= nr_cpu_ids)
return -EINVAL;
if (!smp_startup_cpu(nr))
return -ENOENT;
/*
* The processor is currently spinning, waiting for the
* cpu_start field to become non-zero After we set cpu_start,
* the processor will continue on to secondary_start
*/
paca_ptrs[nr]->cpu_start = 1;
return 0;
}
static int pseries_smp_prepare_cpu(int cpu)
{
if (xive_enabled())
return xive_smp_prepare_cpu(cpu);
return 0;
}
/* Cause IPI as setup by the interrupt controller (xics or xive) */
static void (*ic_cause_ipi)(int cpu) __ro_after_init;
/* Use msgsndp doorbells target is a sibling, else use interrupt controller */
static void dbell_or_ic_cause_ipi(int cpu)
{
if (doorbell_try_core_ipi(cpu))
return;
ic_cause_ipi(cpu);
}
static int pseries_cause_nmi_ipi(int cpu)
{
int hwcpu;
if (cpu == NMI_IPI_ALL_OTHERS) {
hwcpu = H_SIGNAL_SYS_RESET_ALL_OTHERS;
} else {
if (cpu < 0) {
WARN_ONCE(true, "incorrect cpu parameter %d", cpu);
return 0;
}
hwcpu = get_hard_smp_processor_id(cpu);
}
if (plpar_signal_sys_reset(hwcpu) == H_SUCCESS)
return 1;
return 0;
}
static __init void pSeries_smp_probe(void)
{
if (xive_enabled())
xive_smp_probe();
else
xics_smp_probe();
/* No doorbell facility, must use the interrupt controller for IPIs */
if (!cpu_has_feature(CPU_FTR_DBELL))
return;
/* Doorbells can only be used for IPIs between SMT siblings */
if (!cpu_has_feature(CPU_FTR_SMT))
return;
check_kvm_guest();
if (is_kvm_guest()) {
/*
* KVM emulates doorbells by disabling FSCR[MSGP] so msgsndp
* faults to the hypervisor which then reads the instruction
* from guest memory, which tends to be slower than using XIVE.
*/
if (xive_enabled())
return;
/*
* XICS hcalls aren't as fast, so we can use msgsndp (which
* also helps exercise KVM emulation), however KVM can't
* emulate secure guests because it can't read the instruction
* out of their memory.
*/
if (is_secure_guest())
return;
}
/*
* Under PowerVM, FSCR[MSGP] is enabled as guest vCPU siblings are
* gang scheduled on the same physical core, so doorbells are always
* faster than the interrupt controller, and they can be used by
* secure guests.
*/
ic_cause_ipi = smp_ops->cause_ipi;
smp_ops->cause_ipi = dbell_or_ic_cause_ipi;
}
static struct smp_ops_t pseries_smp_ops = {
.message_pass = NULL, /* Use smp_muxed_ipi_message_pass */
.cause_ipi = NULL, /* Filled at runtime by pSeries_smp_probe() */
.cause_nmi_ipi = pseries_cause_nmi_ipi,
.probe = pSeries_smp_probe,
.prepare_cpu = pseries_smp_prepare_cpu,
.kick_cpu = smp_pSeries_kick_cpu,
.setup_cpu = smp_setup_cpu,
.cpu_bootable = smp_generic_cpu_bootable,
};
/* This is called very early */
void __init smp_init_pseries(void)
{
int i;
pr_debug(" -> smp_init_pSeries()\n");
smp_ops = &pseries_smp_ops;
alloc_bootmem_cpumask_var(&of_spin_mask);
/*
* Mark threads which are still spinning in hold loops
*
* We know prom_init will not have started them if RTAS supports
* query-cpu-stopped-state.
*/
if (rtas_function_token(RTAS_FN_QUERY_CPU_STOPPED_STATE) == RTAS_UNKNOWN_SERVICE) {
if (cpu_has_feature(CPU_FTR_SMT)) {
for_each_present_cpu(i) {
if (cpu_thread_in_core(i) == 0)
cpumask_set_cpu(i, of_spin_mask);
}
} else
cpumask_copy(of_spin_mask, cpu_present_mask);
cpumask_clear_cpu(boot_cpuid, of_spin_mask);
}
pr_debug(" <- smp_init_pSeries()\n");
}
Codebase Browser
linux