1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * SMP support for pSeries machines.
4 *
5 * Dave Engebretsen, Peter Bergner, and
6 * Mike Corrigan {engebret|bergner|mikec}@us.ibm.com
7 *
8 * Plus various changes from other IBM teams...
9 */
10
11
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>
24
25 #include <asm/ptrace.h>
26 #include <linux/atomic.h>
27 #include <asm/irq.h>
28 #include <asm/page.h>
29 #include <asm/io.h>
30 #include <asm/smp.h>
31 #include <asm/paca.h>
32 #include <asm/machdep.h>
33 #include <asm/cputable.h>
34 #include <asm/firmware.h>
35 #include <asm/rtas.h>
36 #include <asm/vdso_datapage.h>
37 #include <asm/cputhreads.h>
38 #include <asm/xics.h>
39 #include <asm/xive.h>
40 #include <asm/dbell.h>
41 #include <asm/plpar_wrappers.h>
42 #include <asm/text-patching.h>
43 #include <asm/svm.h>
44 #include <asm/kvm_guest.h>
45
46 #include "pseries.h"
47
48 /*
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.
51 */
52 static cpumask_var_t of_spin_mask;
53
54 /* Query where a cpu is now. Return codes #defined in plpar_wrappers.h */
smp_query_cpu_stopped(unsigned int pcpu)55 int smp_query_cpu_stopped(unsigned int pcpu)
56 {
57 int cpu_status, status;
58 int qcss_tok = rtas_function_token(RTAS_FN_QUERY_CPU_STOPPED_STATE);
59
60 if (qcss_tok == RTAS_UNKNOWN_SERVICE) {
61 printk_once(KERN_INFO
62 "Firmware doesn't support query-cpu-stopped-state\n");
63 return QCSS_HARDWARE_ERROR;
64 }
65
66 status = rtas_call(qcss_tok, 1, 2, &cpu_status, pcpu);
67 if (status != 0) {
68 printk(KERN_ERR
69 "RTAS query-cpu-stopped-state failed: %i\n", status);
70 return status;
71 }
72
73 return cpu_status;
74 }
75
76 /**
77 * smp_startup_cpu() - start the given cpu
78 *
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.
82 *
83 * Returns:
84 * 0 - failure
85 * 1 - success
86 */
smp_startup_cpu(unsigned int lcpu)87 static inline int smp_startup_cpu(unsigned int lcpu)
88 {
89 int status;
90 unsigned long start_here =
91 __pa(ppc_function_entry(generic_secondary_smp_init));
92 unsigned int pcpu;
93 int start_cpu;
94
95 if (cpumask_test_cpu(lcpu, of_spin_mask))
96 /* Already started by OF and sitting in spin loop */
97 return 1;
98
99 pcpu = get_hard_smp_processor_id(lcpu);
100
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);
104 return 1;
105 }
106
107 /*
108 * If the RTAS start-cpu token does not exist then presume the
109 * cpu is already spinning.
110 */
111 start_cpu = rtas_function_token(RTAS_FN_START_CPU);
112 if (start_cpu == RTAS_UNKNOWN_SERVICE)
113 return 1;
114
115 status = rtas_call(start_cpu, 3, 1, NULL, pcpu, start_here, pcpu);
116 if (status != 0) {
117 printk(KERN_ERR "start-cpu failed: %i\n", status);
118 return 0;
119 }
120
121 return 1;
122 }
123
smp_setup_cpu(int cpu)124 static void smp_setup_cpu(int cpu)
125 {
126 if (xive_enabled())
127 xive_smp_setup_cpu();
128 else if (cpu != boot_cpuid)
129 xics_setup_cpu();
130
131 /*
132 * Initialize VPA on non-boot cpus since boot-cpu vpa was
133 * already initialized in pSeries_setup_arch()
134 */
135 if (firmware_has_feature(FW_FEATURE_SPLPAR) &&
136 cpu != boot_cpuid)
137 vpa_init(cpu);
138
139 cpumask_clear_cpu(cpu, of_spin_mask);
140 }
141
smp_pSeries_kick_cpu(int nr)142 static int smp_pSeries_kick_cpu(int nr)
143 {
144 if (nr < 0 || nr >= nr_cpu_ids)
145 return -EINVAL;
146
147 if (!smp_startup_cpu(nr))
148 return -ENOENT;
149
150 /*
151 * The processor is currently spinning, waiting for the
152 * cpu_start field to become non-zero After we set cpu_start,
153 * the processor will continue on to secondary_start
154 */
155 paca_ptrs[nr]->cpu_start = 1;
156
157 return 0;
158 }
159
pseries_smp_prepare_cpu(int cpu)160 static int pseries_smp_prepare_cpu(int cpu)
161 {
162 if (xive_enabled())
163 return xive_smp_prepare_cpu(cpu);
164 return 0;
165 }
166
167 /* Cause IPI as setup by the interrupt controller (xics or xive) */
168 static void (*ic_cause_ipi)(int cpu) __ro_after_init;
169
170 /* Use msgsndp doorbells target is a sibling, else use interrupt controller */
dbell_or_ic_cause_ipi(int cpu)171 static void dbell_or_ic_cause_ipi(int cpu)
172 {
173 if (doorbell_try_core_ipi(cpu))
174 return;
175
176 ic_cause_ipi(cpu);
177 }
178
pseries_cause_nmi_ipi(int cpu)179 static int pseries_cause_nmi_ipi(int cpu)
180 {
181 int hwcpu;
182
183 if (cpu == NMI_IPI_ALL_OTHERS) {
184 hwcpu = H_SIGNAL_SYS_RESET_ALL_OTHERS;
185 } else {
186 if (cpu < 0) {
187 WARN_ONCE(true, "incorrect cpu parameter %d", cpu);
188 return 0;
189 }
190
191 hwcpu = get_hard_smp_processor_id(cpu);
192 }
193
194 if (plpar_signal_sys_reset(hwcpu) == H_SUCCESS)
195 return 1;
196
197 return 0;
198 }
199
pSeries_smp_probe(void)200 static __init void pSeries_smp_probe(void)
201 {
202 if (xive_enabled()) {
203 if (xive_smp_probe() < 0)
204 return;
205 } else {
206 xics_smp_probe();
207 }
208
209 /* No doorbell facility, must use the interrupt controller for IPIs */
210 if (!cpu_has_feature(CPU_FTR_DBELL))
211 return;
212
213 /* Doorbells can only be used for IPIs between SMT siblings */
214 if (!cpu_has_feature(CPU_FTR_SMT))
215 return;
216
217 check_kvm_guest();
218
219 if (is_kvm_guest()) {
220 /*
221 * KVM emulates doorbells by disabling FSCR[MSGP] so msgsndp
222 * faults to the hypervisor which then reads the instruction
223 * from guest memory, which tends to be slower than using XIVE.
224 */
225 if (xive_enabled())
226 return;
227
228 /*
229 * XICS hcalls aren't as fast, so we can use msgsndp (which
230 * also helps exercise KVM emulation), however KVM can't
231 * emulate secure guests because it can't read the instruction
232 * out of their memory.
233 */
234 if (is_secure_guest())
235 return;
236 }
237
238 /*
239 * Under PowerVM, FSCR[MSGP] is enabled as guest vCPU siblings are
240 * gang scheduled on the same physical core, so doorbells are always
241 * faster than the interrupt controller, and they can be used by
242 * secure guests.
243 */
244
245 ic_cause_ipi = smp_ops->cause_ipi;
246 smp_ops->cause_ipi = dbell_or_ic_cause_ipi;
247 }
248
249 static struct smp_ops_t pseries_smp_ops = {
250 .message_pass = NULL, /* Use smp_muxed_ipi_message_pass */
251 .cause_ipi = NULL, /* Filled at runtime by pSeries_smp_probe() */
252 .cause_nmi_ipi = pseries_cause_nmi_ipi,
253 .probe = pSeries_smp_probe,
254 .prepare_cpu = pseries_smp_prepare_cpu,
255 .kick_cpu = smp_pSeries_kick_cpu,
256 .setup_cpu = smp_setup_cpu,
257 .cpu_bootable = smp_generic_cpu_bootable,
258 };
259
260 /* This is called very early */
smp_init_pseries(void)261 void __init smp_init_pseries(void)
262 {
263 int i;
264
265 pr_debug(" -> smp_init_pSeries()\n");
266 smp_ops = &pseries_smp_ops;
267
268 alloc_bootmem_cpumask_var(&of_spin_mask);
269
270 /*
271 * Mark threads which are still spinning in hold loops
272 *
273 * We know prom_init will not have started them if RTAS supports
274 * query-cpu-stopped-state.
275 */
276 if (rtas_function_token(RTAS_FN_QUERY_CPU_STOPPED_STATE) == RTAS_UNKNOWN_SERVICE) {
277 if (cpu_has_feature(CPU_FTR_SMT)) {
278 for_each_present_cpu(i) {
279 if (cpu_thread_in_core(i) == 0)
280 cpumask_set_cpu(i, of_spin_mask);
281 }
282 } else
283 cpumask_copy(of_spin_mask, cpu_present_mask);
284
285 cpumask_clear_cpu(boot_cpuid, of_spin_mask);
286 }
287
288 pr_debug(" <- smp_init_pSeries()\n");
289 }
290