1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * SMP support for pSeries machines.
5 * Dave Engebretsen, Peter Bergner, and
6 * Mike Corrigan {engebret|bergner|mikec}@us.ibm.com
8 * Plus various changes from other IBM teams...
12 #include <linux/kernel.h>
13 #include <linux/sched.h>
14 #include <linux/smp.h>
15 #include <linux/interrupt.h>
16 #include <linux/delay.h>
17 #include <linux/init.h>
18 #include <linux/spinlock.h>
19 #include <linux/cache.h>
20 #include <linux/err.h>
21 #include <linux/device.h>
22 #include <linux/cpu.h>
23 #include <linux/pgtable.h>
25 #include <asm/ptrace.h>
26 #include <linux/atomic.h>
32 #include <asm/machdep.h>
33 #include <asm/cputable.h>
34 #include <asm/firmware.h>
36 #include <asm/vdso_datapage.h>
37 #include <asm/cputhreads.h>
40 #include <asm/dbell.h>
41 #include <asm/plpar_wrappers.h>
42 #include <asm/code-patching.h>
44 #include <asm/kvm_guest.h>
49 * The Primary thread of each non-boot processor was started from the OF client
50 * interface by prom_hold_cpus and is spinning on secondary_hold_spinloop.
52 static cpumask_var_t of_spin_mask;
54 /* Query where a cpu is now. Return codes #defined in plpar_wrappers.h */
55 int smp_query_cpu_stopped(unsigned int pcpu)
57 int cpu_status, status;
58 int qcss_tok = rtas_function_token(RTAS_FN_QUERY_CPU_STOPPED_STATE);
60 if (qcss_tok == RTAS_UNKNOWN_SERVICE) {
62 "Firmware doesn't support query-cpu-stopped-state\n");
63 return QCSS_HARDWARE_ERROR;
66 status = rtas_call(qcss_tok, 1, 2, &cpu_status, pcpu);
69 "RTAS query-cpu-stopped-state failed: %i\n", status);
77 * smp_startup_cpu() - start the given cpu
79 * At boot time, there is nothing to do for primary threads which were
80 * started from Open Firmware. For anything else, call RTAS with the
81 * appropriate start location.
87 static inline int smp_startup_cpu(unsigned int lcpu)
90 unsigned long start_here =
91 __pa(ppc_function_entry(generic_secondary_smp_init));
95 if (cpumask_test_cpu(lcpu, of_spin_mask))
96 /* Already started by OF and sitting in spin loop */
99 pcpu = get_hard_smp_processor_id(lcpu);
101 /* Check to see if the CPU out of FW already for kexec */
102 if (smp_query_cpu_stopped(pcpu) == QCSS_NOT_STOPPED){
103 cpumask_set_cpu(lcpu, of_spin_mask);
108 * If the RTAS start-cpu token does not exist then presume the
109 * cpu is already spinning.
111 start_cpu = rtas_function_token(RTAS_FN_START_CPU);
112 if (start_cpu == RTAS_UNKNOWN_SERVICE)
115 status = rtas_call(start_cpu, 3, 1, NULL, pcpu, start_here, pcpu);
117 printk(KERN_ERR "start-cpu failed: %i\n", status);
124 static void smp_setup_cpu(int cpu)
127 xive_smp_setup_cpu();
128 else if (cpu != boot_cpuid)
131 if (firmware_has_feature(FW_FEATURE_SPLPAR))
134 cpumask_clear_cpu(cpu, of_spin_mask);
137 static int smp_pSeries_kick_cpu(int nr)
139 if (nr < 0 || nr >= nr_cpu_ids)
142 if (!smp_startup_cpu(nr))
146 * The processor is currently spinning, waiting for the
147 * cpu_start field to become non-zero After we set cpu_start,
148 * the processor will continue on to secondary_start
150 paca_ptrs[nr]->cpu_start = 1;
155 static int pseries_smp_prepare_cpu(int cpu)
158 return xive_smp_prepare_cpu(cpu);
162 /* Cause IPI as setup by the interrupt controller (xics or xive) */
163 static void (*ic_cause_ipi)(int cpu) __ro_after_init;
165 /* Use msgsndp doorbells target is a sibling, else use interrupt controller */
166 static void dbell_or_ic_cause_ipi(int cpu)
168 if (doorbell_try_core_ipi(cpu))
174 static int pseries_cause_nmi_ipi(int cpu)
178 if (cpu == NMI_IPI_ALL_OTHERS) {
179 hwcpu = H_SIGNAL_SYS_RESET_ALL_OTHERS;
182 WARN_ONCE(true, "incorrect cpu parameter %d", cpu);
186 hwcpu = get_hard_smp_processor_id(cpu);
189 if (plpar_signal_sys_reset(hwcpu) == H_SUCCESS)
195 static __init void pSeries_smp_probe(void)
202 /* No doorbell facility, must use the interrupt controller for IPIs */
203 if (!cpu_has_feature(CPU_FTR_DBELL))
206 /* Doorbells can only be used for IPIs between SMT siblings */
207 if (!cpu_has_feature(CPU_FTR_SMT))
212 if (is_kvm_guest()) {
214 * KVM emulates doorbells by disabling FSCR[MSGP] so msgsndp
215 * faults to the hypervisor which then reads the instruction
216 * from guest memory, which tends to be slower than using XIVE.
222 * XICS hcalls aren't as fast, so we can use msgsndp (which
223 * also helps exercise KVM emulation), however KVM can't
224 * emulate secure guests because it can't read the instruction
225 * out of their memory.
227 if (is_secure_guest())
232 * Under PowerVM, FSCR[MSGP] is enabled as guest vCPU siblings are
233 * gang scheduled on the same physical core, so doorbells are always
234 * faster than the interrupt controller, and they can be used by
238 ic_cause_ipi = smp_ops->cause_ipi;
239 smp_ops->cause_ipi = dbell_or_ic_cause_ipi;
242 static struct smp_ops_t pseries_smp_ops = {
243 .message_pass = NULL, /* Use smp_muxed_ipi_message_pass */
244 .cause_ipi = NULL, /* Filled at runtime by pSeries_smp_probe() */
245 .cause_nmi_ipi = pseries_cause_nmi_ipi,
246 .probe = pSeries_smp_probe,
247 .prepare_cpu = pseries_smp_prepare_cpu,
248 .kick_cpu = smp_pSeries_kick_cpu,
249 .setup_cpu = smp_setup_cpu,
250 .cpu_bootable = smp_generic_cpu_bootable,
253 /* This is called very early */
254 void __init smp_init_pseries(void)
258 pr_debug(" -> smp_init_pSeries()\n");
259 smp_ops = &pseries_smp_ops;
261 alloc_bootmem_cpumask_var(&of_spin_mask);
264 * Mark threads which are still spinning in hold loops
266 * We know prom_init will not have started them if RTAS supports
267 * query-cpu-stopped-state.
269 if (rtas_function_token(RTAS_FN_QUERY_CPU_STOPPED_STATE) == RTAS_UNKNOWN_SERVICE) {
270 if (cpu_has_feature(CPU_FTR_SMT)) {
271 for_each_present_cpu(i) {
272 if (cpu_thread_in_core(i) == 0)
273 cpumask_set_cpu(i, of_spin_mask);
276 cpumask_copy(of_spin_mask, cpu_present_mask);
278 cpumask_clear_cpu(boot_cpuid, of_spin_mask);
281 pr_debug(" <- smp_init_pSeries()\n");