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/prom.h>
31 #include <asm/smp.h>
32 #include <asm/paca.h>
33 #include <asm/machdep.h>
34 #include <asm/cputable.h>
35 #include <asm/firmware.h>
36 #include <asm/rtas.h>
37 #include <asm/vdso_datapage.h>
38 #include <asm/cputhreads.h>
39 #include <asm/xics.h>
40 #include <asm/xive.h>
41 #include <asm/dbell.h>
42 #include <asm/plpar_wrappers.h>
43 #include <asm/code-patching.h>
44 #include <asm/svm.h>
45 #include <asm/kvm_guest.h>
46
47 #include "pseries.h"
48
49 /*
50 * The Primary thread of each non-boot processor was started from the OF client
51 * interface by prom_hold_cpus and is spinning on secondary_hold_spinloop.
52 */
53 static cpumask_var_t of_spin_mask;
54
55 /* Query where a cpu is now. Return codes #defined in plpar_wrappers.h */
smp_query_cpu_stopped(unsigned int pcpu)56 int smp_query_cpu_stopped(unsigned int pcpu)
57 {
58 int cpu_status, status;
59 int qcss_tok = rtas_token("query-cpu-stopped-state");
60
61 if (qcss_tok == RTAS_UNKNOWN_SERVICE) {
62 printk_once(KERN_INFO
63 "Firmware doesn't support query-cpu-stopped-state\n");
64 return QCSS_HARDWARE_ERROR;
65 }
66
67 status = rtas_call(qcss_tok, 1, 2, &cpu_status, pcpu);
68 if (status != 0) {
69 printk(KERN_ERR
70 "RTAS query-cpu-stopped-state failed: %i\n", status);
71 return status;
72 }
73
74 return cpu_status;
75 }
76
77 /**
78 * smp_startup_cpu() - start the given cpu
79 *
80 * At boot time, there is nothing to do for primary threads which were
81 * started from Open Firmware. For anything else, call RTAS with the
82 * appropriate start location.
83 *
84 * Returns:
85 * 0 - failure
86 * 1 - success
87 */
smp_startup_cpu(unsigned int lcpu)88 static inline int smp_startup_cpu(unsigned int lcpu)
89 {
90 int status;
91 unsigned long start_here =
92 __pa(ppc_function_entry(generic_secondary_smp_init));
93 unsigned int pcpu;
94 int start_cpu;
95
96 if (cpumask_test_cpu(lcpu, of_spin_mask))
97 /* Already started by OF and sitting in spin loop */
98 return 1;
99
100 pcpu = get_hard_smp_processor_id(lcpu);
101
102 /* Check to see if the CPU out of FW already for kexec */
103 if (smp_query_cpu_stopped(pcpu) == QCSS_NOT_STOPPED){
104 cpumask_set_cpu(lcpu, of_spin_mask);
105 return 1;
106 }
107
108 /*
109 * If the RTAS start-cpu token does not exist then presume the
110 * cpu is already spinning.
111 */
112 start_cpu = rtas_token("start-cpu");
113 if (start_cpu == RTAS_UNKNOWN_SERVICE)
114 return 1;
115
116 status = rtas_call(start_cpu, 3, 1, NULL, pcpu, start_here, pcpu);
117 if (status != 0) {
118 printk(KERN_ERR "start-cpu failed: %i\n", status);
119 return 0;
120 }
121
122 return 1;
123 }
124
smp_setup_cpu(int cpu)125 static void smp_setup_cpu(int cpu)
126 {
127 if (xive_enabled())
128 xive_smp_setup_cpu();
129 else if (cpu != boot_cpuid)
130 xics_setup_cpu();
131
132 if (firmware_has_feature(FW_FEATURE_SPLPAR))
133 vpa_init(cpu);
134
135 cpumask_clear_cpu(cpu, of_spin_mask);
136 }
137
smp_pSeries_kick_cpu(int nr)138 static int smp_pSeries_kick_cpu(int nr)
139 {
140 if (nr < 0 || nr >= nr_cpu_ids)
141 return -EINVAL;
142
143 if (!smp_startup_cpu(nr))
144 return -ENOENT;
145
146 /*
147 * The processor is currently spinning, waiting for the
148 * cpu_start field to become non-zero After we set cpu_start,
149 * the processor will continue on to secondary_start
150 */
151 paca_ptrs[nr]->cpu_start = 1;
152
153 return 0;
154 }
155
pseries_smp_prepare_cpu(int cpu)156 static int pseries_smp_prepare_cpu(int cpu)
157 {
158 if (xive_enabled())
159 return xive_smp_prepare_cpu(cpu);
160 return 0;
161 }
162
163 /* Cause IPI as setup by the interrupt controller (xics or xive) */
164 static void (*ic_cause_ipi)(int cpu) __ro_after_init;
165
166 /* Use msgsndp doorbells target is a sibling, else use interrupt controller */
dbell_or_ic_cause_ipi(int cpu)167 static void dbell_or_ic_cause_ipi(int cpu)
168 {
169 if (doorbell_try_core_ipi(cpu))
170 return;
171
172 ic_cause_ipi(cpu);
173 }
174
pseries_cause_nmi_ipi(int cpu)175 static int pseries_cause_nmi_ipi(int cpu)
176 {
177 int hwcpu;
178
179 if (cpu == NMI_IPI_ALL_OTHERS) {
180 hwcpu = H_SIGNAL_SYS_RESET_ALL_OTHERS;
181 } else {
182 if (cpu < 0) {
183 WARN_ONCE(true, "incorrect cpu parameter %d", cpu);
184 return 0;
185 }
186
187 hwcpu = get_hard_smp_processor_id(cpu);
188 }
189
190 if (plpar_signal_sys_reset(hwcpu) == H_SUCCESS)
191 return 1;
192
193 return 0;
194 }
195
pSeries_smp_probe(void)196 static __init void pSeries_smp_probe(void)
197 {
198 if (xive_enabled())
199 xive_smp_probe();
200 else
201 xics_smp_probe();
202
203 /* No doorbell facility, must use the interrupt controller for IPIs */
204 if (!cpu_has_feature(CPU_FTR_DBELL))
205 return;
206
207 /* Doorbells can only be used for IPIs between SMT siblings */
208 if (!cpu_has_feature(CPU_FTR_SMT))
209 return;
210
211 check_kvm_guest();
212
213 if (is_kvm_guest()) {
214 /*
215 * KVM emulates doorbells by disabling FSCR[MSGP] so msgsndp
216 * faults to the hypervisor which then reads the instruction
217 * from guest memory, which tends to be slower than using XIVE.
218 */
219 if (xive_enabled())
220 return;
221
222 /*
223 * XICS hcalls aren't as fast, so we can use msgsndp (which
224 * also helps exercise KVM emulation), however KVM can't
225 * emulate secure guests because it can't read the instruction
226 * out of their memory.
227 */
228 if (is_secure_guest())
229 return;
230 }
231
232 /*
233 * Under PowerVM, FSCR[MSGP] is enabled as guest vCPU siblings are
234 * gang scheduled on the same physical core, so doorbells are always
235 * faster than the interrupt controller, and they can be used by
236 * secure guests.
237 */
238
239 ic_cause_ipi = smp_ops->cause_ipi;
240 smp_ops->cause_ipi = dbell_or_ic_cause_ipi;
241 }
242
243 static struct smp_ops_t pseries_smp_ops = {
244 .message_pass = NULL, /* Use smp_muxed_ipi_message_pass */
245 .cause_ipi = NULL, /* Filled at runtime by pSeries_smp_probe() */
246 .cause_nmi_ipi = pseries_cause_nmi_ipi,
247 .probe = pSeries_smp_probe,
248 .prepare_cpu = pseries_smp_prepare_cpu,
249 .kick_cpu = smp_pSeries_kick_cpu,
250 .setup_cpu = smp_setup_cpu,
251 .cpu_bootable = smp_generic_cpu_bootable,
252 };
253
254 /* This is called very early */
smp_init_pseries(void)255 void __init smp_init_pseries(void)
256 {
257 int i;
258
259 pr_debug(" -> smp_init_pSeries()\n");
260 smp_ops = &pseries_smp_ops;
261
262 alloc_bootmem_cpumask_var(&of_spin_mask);
263
264 /*
265 * Mark threads which are still spinning in hold loops
266 *
267 * We know prom_init will not have started them if RTAS supports
268 * query-cpu-stopped-state.
269 */
270 if (rtas_token("query-cpu-stopped-state") == RTAS_UNKNOWN_SERVICE) {
271 if (cpu_has_feature(CPU_FTR_SMT)) {
272 for_each_present_cpu(i) {
273 if (cpu_thread_in_core(i) == 0)
274 cpumask_set_cpu(i, of_spin_mask);
275 }
276 } else
277 cpumask_copy(of_spin_mask, cpu_present_mask);
278
279 cpumask_clear_cpu(boot_cpuid, of_spin_mask);
280 }
281
282 /* Non-lpar has additional take/give timebase */
283 if (rtas_token("freeze-time-base") != RTAS_UNKNOWN_SERVICE) {
284 smp_ops->give_timebase = rtas_give_timebase;
285 smp_ops->take_timebase = rtas_take_timebase;
286 }
287
288 pr_debug(" <- smp_init_pSeries()\n");
289 }
290