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 */
53static cpumask_var_t of_spin_mask;
54
55/* Query where a cpu is now.  Return codes #defined in plpar_wrappers.h */
56int 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 */
88static 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
125static 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
138static 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
156static 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) */
164static void (*ic_cause_ipi)(int cpu) __ro_after_init;
165
166/* Use msgsndp doorbells target is a sibling, else use interrupt controller */
167static 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
175static 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
196static __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
243static 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 */
255void __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