1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * SMP support for PowerNV machines.
4  *
5  * Copyright 2011 IBM Corp.
6  */
7 
8 #include <linux/kernel.h>
9 #include <linux/module.h>
10 #include <linux/sched.h>
11 #include <linux/sched/hotplug.h>
12 #include <linux/smp.h>
13 #include <linux/interrupt.h>
14 #include <linux/delay.h>
15 #include <linux/init.h>
16 #include <linux/spinlock.h>
17 #include <linux/cpu.h>
18 
19 #include <asm/irq.h>
20 #include <asm/smp.h>
21 #include <asm/paca.h>
22 #include <asm/machdep.h>
23 #include <asm/cputable.h>
24 #include <asm/firmware.h>
25 #include <asm/vdso_datapage.h>
26 #include <asm/cputhreads.h>
27 #include <asm/xics.h>
28 #include <asm/xive.h>
29 #include <asm/opal.h>
30 #include <asm/runlatch.h>
31 #include <asm/code-patching.h>
32 #include <asm/dbell.h>
33 #include <asm/kvm_ppc.h>
34 #include <asm/ppc-opcode.h>
35 #include <asm/cpuidle.h>
36 #include <asm/kexec.h>
37 #include <asm/reg.h>
38 #include <asm/powernv.h>
39 
40 #include "powernv.h"
41 
42 #ifdef DEBUG
43 #include <asm/udbg.h>
44 #define DBG(fmt...) udbg_printf(fmt)
45 #else
46 #define DBG(fmt...) do { } while (0)
47 #endif
48 
49 static void pnv_smp_setup_cpu(int cpu)
50 {
51 	/*
52 	 * P9 workaround for CI vector load (see traps.c),
53 	 * enable the corresponding HMI interrupt
54 	 */
55 	if (pvr_version_is(PVR_POWER9))
56 		mtspr(SPRN_HMEER, mfspr(SPRN_HMEER) | PPC_BIT(17));
57 
58 	if (xive_enabled())
59 		xive_smp_setup_cpu();
60 	else if (cpu != boot_cpuid)
61 		xics_setup_cpu();
62 }
63 
64 static int pnv_smp_kick_cpu(int nr)
65 {
66 	unsigned int pcpu;
67 	unsigned long start_here =
68 			__pa(ppc_function_entry(generic_secondary_smp_init));
69 	long rc;
70 	uint8_t status;
71 
72 	if (nr < 0 || nr >= nr_cpu_ids)
73 		return -EINVAL;
74 
75 	pcpu = get_hard_smp_processor_id(nr);
76 	/*
77 	 * If we already started or OPAL is not supported, we just
78 	 * kick the CPU via the PACA
79 	 */
80 	if (paca_ptrs[nr]->cpu_start || !firmware_has_feature(FW_FEATURE_OPAL))
81 		goto kick;
82 
83 	/*
84 	 * At this point, the CPU can either be spinning on the way in
85 	 * from kexec or be inside OPAL waiting to be started for the
86 	 * first time. OPAL v3 allows us to query OPAL to know if it
87 	 * has the CPUs, so we do that
88 	 */
89 	rc = opal_query_cpu_status(pcpu, &status);
90 	if (rc != OPAL_SUCCESS) {
91 		pr_warn("OPAL Error %ld querying CPU %d state\n", rc, nr);
92 		return -ENODEV;
93 	}
94 
95 	/*
96 	 * Already started, just kick it, probably coming from
97 	 * kexec and spinning
98 	 */
99 	if (status == OPAL_THREAD_STARTED)
100 		goto kick;
101 
102 	/*
103 	 * Available/inactive, let's kick it
104 	 */
105 	if (status == OPAL_THREAD_INACTIVE) {
106 		pr_devel("OPAL: Starting CPU %d (HW 0x%x)...\n", nr, pcpu);
107 		rc = opal_start_cpu(pcpu, start_here);
108 		if (rc != OPAL_SUCCESS) {
109 			pr_warn("OPAL Error %ld starting CPU %d\n", rc, nr);
110 			return -ENODEV;
111 		}
112 	} else {
113 		/*
114 		 * An unavailable CPU (or any other unknown status)
115 		 * shouldn't be started. It should also
116 		 * not be in the possible map but currently it can
117 		 * happen
118 		 */
119 		pr_devel("OPAL: CPU %d (HW 0x%x) is unavailable"
120 			 " (status %d)...\n", nr, pcpu, status);
121 		return -ENODEV;
122 	}
123 
124 kick:
125 	return smp_generic_kick_cpu(nr);
126 }
127 
128 #ifdef CONFIG_HOTPLUG_CPU
129 
130 static int pnv_smp_cpu_disable(void)
131 {
132 	int cpu = smp_processor_id();
133 
134 	/* This is identical to pSeries... might consolidate by
135 	 * moving migrate_irqs_away to a ppc_md with default to
136 	 * the generic fixup_irqs. --BenH.
137 	 */
138 	set_cpu_online(cpu, false);
139 	vdso_data->processorCount--;
140 	if (cpu == boot_cpuid)
141 		boot_cpuid = cpumask_any(cpu_online_mask);
142 	if (xive_enabled())
143 		xive_smp_disable_cpu();
144 	else
145 		xics_migrate_irqs_away();
146 
147 	cleanup_cpu_mmu_context();
148 
149 	return 0;
150 }
151 
152 static void pnv_flush_interrupts(void)
153 {
154 	if (cpu_has_feature(CPU_FTR_ARCH_300)) {
155 		if (xive_enabled())
156 			xive_flush_interrupt();
157 		else
158 			icp_opal_flush_interrupt();
159 	} else {
160 		icp_native_flush_interrupt();
161 	}
162 }
163 
164 static void pnv_cpu_offline_self(void)
165 {
166 	unsigned long srr1, unexpected_mask, wmask;
167 	unsigned int cpu;
168 	u64 lpcr_val;
169 
170 	/* Standard hot unplug procedure */
171 
172 	idle_task_exit();
173 	cpu = smp_processor_id();
174 	DBG("CPU%d offline\n", cpu);
175 	generic_set_cpu_dead(cpu);
176 	smp_wmb();
177 
178 	wmask = SRR1_WAKEMASK;
179 	if (cpu_has_feature(CPU_FTR_ARCH_207S))
180 		wmask = SRR1_WAKEMASK_P8;
181 
182 	/*
183 	 * This turns the irq soft-disabled state we're called with, into a
184 	 * hard-disabled state with pending irq_happened interrupts cleared.
185 	 *
186 	 * PACA_IRQ_DEC   - Decrementer should be ignored.
187 	 * PACA_IRQ_HMI   - Can be ignored, processing is done in real mode.
188 	 * PACA_IRQ_DBELL, EE, PMI - Unexpected.
189 	 */
190 	hard_irq_disable();
191 	if (generic_check_cpu_restart(cpu))
192 		goto out;
193 
194 	unexpected_mask = ~(PACA_IRQ_DEC | PACA_IRQ_HMI | PACA_IRQ_HARD_DIS);
195 	if (local_paca->irq_happened & unexpected_mask) {
196 		if (local_paca->irq_happened & PACA_IRQ_EE)
197 			pnv_flush_interrupts();
198 		DBG("CPU%d Unexpected exit while offline irq_happened=%lx!\n",
199 				cpu, local_paca->irq_happened);
200 	}
201 	local_paca->irq_happened = PACA_IRQ_HARD_DIS;
202 
203 	/*
204 	 * We don't want to take decrementer interrupts while we are
205 	 * offline, so clear LPCR:PECE1. We keep PECE2 (and
206 	 * LPCR_PECE_HVEE on P9) enabled so as to let IPIs in.
207 	 *
208 	 * If the CPU gets woken up by a special wakeup, ensure that
209 	 * the SLW engine sets LPCR with decrementer bit cleared, else
210 	 * the CPU will come back to the kernel due to a spurious
211 	 * wakeup.
212 	 */
213 	lpcr_val = mfspr(SPRN_LPCR) & ~(u64)LPCR_PECE1;
214 	pnv_program_cpu_hotplug_lpcr(cpu, lpcr_val);
215 
216 	while (!generic_check_cpu_restart(cpu)) {
217 		/*
218 		 * Clear IPI flag, since we don't handle IPIs while
219 		 * offline, except for those when changing micro-threading
220 		 * mode, which are handled explicitly below, and those
221 		 * for coming online, which are handled via
222 		 * generic_check_cpu_restart() calls.
223 		 */
224 		kvmppc_clear_host_ipi(cpu);
225 
226 		srr1 = pnv_cpu_offline(cpu);
227 
228 		WARN_ON_ONCE(!irqs_disabled());
229 		WARN_ON(lazy_irq_pending());
230 
231 		/*
232 		 * If the SRR1 value indicates that we woke up due to
233 		 * an external interrupt, then clear the interrupt.
234 		 * We clear the interrupt before checking for the
235 		 * reason, so as to avoid a race where we wake up for
236 		 * some other reason, find nothing and clear the interrupt
237 		 * just as some other cpu is sending us an interrupt.
238 		 * If we returned from power7_nap as a result of
239 		 * having finished executing in a KVM guest, then srr1
240 		 * contains 0.
241 		 */
242 		if (((srr1 & wmask) == SRR1_WAKEEE) ||
243 		    ((srr1 & wmask) == SRR1_WAKEHVI)) {
244 			pnv_flush_interrupts();
245 		} else if ((srr1 & wmask) == SRR1_WAKEHDBELL) {
246 			unsigned long msg = PPC_DBELL_TYPE(PPC_DBELL_SERVER);
247 			asm volatile(PPC_MSGCLR(%0) : : "r" (msg));
248 		} else if ((srr1 & wmask) == SRR1_WAKERESET) {
249 			irq_set_pending_from_srr1(srr1);
250 			/* Does not return */
251 		}
252 
253 		smp_mb();
254 
255 		/*
256 		 * For kdump kernels, we process the ipi and jump to
257 		 * crash_ipi_callback
258 		 */
259 		if (kdump_in_progress()) {
260 			/*
261 			 * If we got to this point, we've not used
262 			 * NMI's, otherwise we would have gone
263 			 * via the SRR1_WAKERESET path. We are
264 			 * using regular IPI's for waking up offline
265 			 * threads.
266 			 */
267 			struct pt_regs regs;
268 
269 			ppc_save_regs(&regs);
270 			crash_ipi_callback(&regs);
271 			/* Does not return */
272 		}
273 
274 		if (cpu_core_split_required())
275 			continue;
276 
277 		if (srr1 && !generic_check_cpu_restart(cpu))
278 			DBG("CPU%d Unexpected exit while offline srr1=%lx!\n",
279 					cpu, srr1);
280 
281 	}
282 
283 	/*
284 	 * Re-enable decrementer interrupts in LPCR.
285 	 *
286 	 * Further, we want stop states to be woken up by decrementer
287 	 * for non-hotplug cases. So program the LPCR via stop api as
288 	 * well.
289 	 */
290 	lpcr_val = mfspr(SPRN_LPCR) | (u64)LPCR_PECE1;
291 	pnv_program_cpu_hotplug_lpcr(cpu, lpcr_val);
292 out:
293 	DBG("CPU%d coming online...\n", cpu);
294 }
295 
296 #endif /* CONFIG_HOTPLUG_CPU */
297 
298 static int pnv_cpu_bootable(unsigned int nr)
299 {
300 	/*
301 	 * Starting with POWER8, the subcore logic relies on all threads of a
302 	 * core being booted so that they can participate in split mode
303 	 * switches. So on those machines we ignore the smt_enabled_at_boot
304 	 * setting (smt-enabled on the kernel command line).
305 	 */
306 	if (cpu_has_feature(CPU_FTR_ARCH_207S))
307 		return 1;
308 
309 	return smp_generic_cpu_bootable(nr);
310 }
311 
312 static int pnv_smp_prepare_cpu(int cpu)
313 {
314 	if (xive_enabled())
315 		return xive_smp_prepare_cpu(cpu);
316 	return 0;
317 }
318 
319 /* Cause IPI as setup by the interrupt controller (xics or xive) */
320 static void (*ic_cause_ipi)(int cpu);
321 
322 static void pnv_cause_ipi(int cpu)
323 {
324 	if (doorbell_try_core_ipi(cpu))
325 		return;
326 
327 	ic_cause_ipi(cpu);
328 }
329 
330 static void __init pnv_smp_probe(void)
331 {
332 	if (xive_enabled())
333 		xive_smp_probe();
334 	else
335 		xics_smp_probe();
336 
337 	if (cpu_has_feature(CPU_FTR_DBELL)) {
338 		ic_cause_ipi = smp_ops->cause_ipi;
339 		WARN_ON(!ic_cause_ipi);
340 
341 		if (cpu_has_feature(CPU_FTR_ARCH_300))
342 			smp_ops->cause_ipi = doorbell_global_ipi;
343 		else
344 			smp_ops->cause_ipi = pnv_cause_ipi;
345 	}
346 }
347 
348 noinstr static int pnv_system_reset_exception(struct pt_regs *regs)
349 {
350 	if (smp_handle_nmi_ipi(regs))
351 		return 1;
352 	return 0;
353 }
354 
355 static int pnv_cause_nmi_ipi(int cpu)
356 {
357 	int64_t rc;
358 
359 	if (cpu >= 0) {
360 		int h = get_hard_smp_processor_id(cpu);
361 
362 		if (opal_check_token(OPAL_QUIESCE))
363 			opal_quiesce(QUIESCE_HOLD, h);
364 
365 		rc = opal_signal_system_reset(h);
366 
367 		if (opal_check_token(OPAL_QUIESCE))
368 			opal_quiesce(QUIESCE_RESUME, h);
369 
370 		if (rc != OPAL_SUCCESS)
371 			return 0;
372 		return 1;
373 
374 	} else if (cpu == NMI_IPI_ALL_OTHERS) {
375 		bool success = true;
376 		int c;
377 
378 		if (opal_check_token(OPAL_QUIESCE))
379 			opal_quiesce(QUIESCE_HOLD, -1);
380 
381 		/*
382 		 * We do not use broadcasts (yet), because it's not clear
383 		 * exactly what semantics Linux wants or the firmware should
384 		 * provide.
385 		 */
386 		for_each_online_cpu(c) {
387 			if (c == smp_processor_id())
388 				continue;
389 
390 			rc = opal_signal_system_reset(
391 						get_hard_smp_processor_id(c));
392 			if (rc != OPAL_SUCCESS)
393 				success = false;
394 		}
395 
396 		if (opal_check_token(OPAL_QUIESCE))
397 			opal_quiesce(QUIESCE_RESUME, -1);
398 
399 		if (success)
400 			return 1;
401 
402 		/*
403 		 * Caller will fall back to doorbells, which may pick
404 		 * up the remainders.
405 		 */
406 	}
407 
408 	return 0;
409 }
410 
411 static struct smp_ops_t pnv_smp_ops = {
412 	.message_pass	= NULL, /* Use smp_muxed_ipi_message_pass */
413 	.cause_ipi	= NULL,	/* Filled at runtime by pnv_smp_probe() */
414 	.cause_nmi_ipi	= NULL,
415 	.probe		= pnv_smp_probe,
416 	.prepare_cpu	= pnv_smp_prepare_cpu,
417 	.kick_cpu	= pnv_smp_kick_cpu,
418 	.setup_cpu	= pnv_smp_setup_cpu,
419 	.cpu_bootable	= pnv_cpu_bootable,
420 #ifdef CONFIG_HOTPLUG_CPU
421 	.cpu_disable	= pnv_smp_cpu_disable,
422 	.cpu_die	= generic_cpu_die,
423 	.cpu_offline_self = pnv_cpu_offline_self,
424 #endif /* CONFIG_HOTPLUG_CPU */
425 };
426 
427 /* This is called very early during platform setup_arch */
428 void __init pnv_smp_init(void)
429 {
430 	if (opal_check_token(OPAL_SIGNAL_SYSTEM_RESET)) {
431 		ppc_md.system_reset_exception = pnv_system_reset_exception;
432 		pnv_smp_ops.cause_nmi_ipi = pnv_cause_nmi_ipi;
433 	}
434 	smp_ops = &pnv_smp_ops;
435 
436 #ifdef CONFIG_HOTPLUG_CPU
437 #ifdef CONFIG_KEXEC_CORE
438 	crash_wake_offline = 1;
439 #endif
440 #endif
441 }
442