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/code-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 */
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  */
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 
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 	if (firmware_has_feature(FW_FEATURE_SPLPAR))
132 		vpa_init(cpu);
133 
134 	cpumask_clear_cpu(cpu, of_spin_mask);
135 }
136 
137 static int smp_pSeries_kick_cpu(int nr)
138 {
139 	if (nr < 0 || nr >= nr_cpu_ids)
140 		return -EINVAL;
141 
142 	if (!smp_startup_cpu(nr))
143 		return -ENOENT;
144 
145 	/*
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
149 	 */
150 	paca_ptrs[nr]->cpu_start = 1;
151 
152 	return 0;
153 }
154 
155 static int pseries_smp_prepare_cpu(int cpu)
156 {
157 	if (xive_enabled())
158 		return xive_smp_prepare_cpu(cpu);
159 	return 0;
160 }
161 
162 /* Cause IPI as setup by the interrupt controller (xics or xive) */
163 static void (*ic_cause_ipi)(int cpu) __ro_after_init;
164 
165 /* Use msgsndp doorbells target is a sibling, else use interrupt controller */
166 static void dbell_or_ic_cause_ipi(int cpu)
167 {
168 	if (doorbell_try_core_ipi(cpu))
169 		return;
170 
171 	ic_cause_ipi(cpu);
172 }
173 
174 static int pseries_cause_nmi_ipi(int cpu)
175 {
176 	int hwcpu;
177 
178 	if (cpu == NMI_IPI_ALL_OTHERS) {
179 		hwcpu = H_SIGNAL_SYS_RESET_ALL_OTHERS;
180 	} else {
181 		if (cpu < 0) {
182 			WARN_ONCE(true, "incorrect cpu parameter %d", cpu);
183 			return 0;
184 		}
185 
186 		hwcpu = get_hard_smp_processor_id(cpu);
187 	}
188 
189 	if (plpar_signal_sys_reset(hwcpu) == H_SUCCESS)
190 		return 1;
191 
192 	return 0;
193 }
194 
195 static __init void pSeries_smp_probe(void)
196 {
197 	if (xive_enabled())
198 		xive_smp_probe();
199 	else
200 		xics_smp_probe();
201 
202 	/* No doorbell facility, must use the interrupt controller for IPIs */
203 	if (!cpu_has_feature(CPU_FTR_DBELL))
204 		return;
205 
206 	/* Doorbells can only be used for IPIs between SMT siblings */
207 	if (!cpu_has_feature(CPU_FTR_SMT))
208 		return;
209 
210 	check_kvm_guest();
211 
212 	if (is_kvm_guest()) {
213 		/*
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.
217 		 */
218 		if (xive_enabled())
219 			return;
220 
221 		/*
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.
226 		 */
227 		if (is_secure_guest())
228 			return;
229 	}
230 
231 	/*
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
235 	 * secure guests.
236 	 */
237 
238 	ic_cause_ipi = smp_ops->cause_ipi;
239 	smp_ops->cause_ipi = dbell_or_ic_cause_ipi;
240 }
241 
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,
251 };
252 
253 /* This is called very early */
254 void __init smp_init_pseries(void)
255 {
256 	int i;
257 
258 	pr_debug(" -> smp_init_pSeries()\n");
259 	smp_ops = &pseries_smp_ops;
260 
261 	alloc_bootmem_cpumask_var(&of_spin_mask);
262 
263 	/*
264 	 * Mark threads which are still spinning in hold loops
265 	 *
266 	 * We know prom_init will not have started them if RTAS supports
267 	 * query-cpu-stopped-state.
268 	 */
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);
274 			}
275 		} else
276 			cpumask_copy(of_spin_mask, cpu_present_mask);
277 
278 		cpumask_clear_cpu(boot_cpuid, of_spin_mask);
279 	}
280 
281 	pr_debug(" <- smp_init_pSeries()\n");
282 }
283