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 */
52static cpumask_var_t of_spin_mask;
53
54/* Query where a cpu is now.  Return codes #defined in plpar_wrappers.h */
55int 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 */
87static 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
124static 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
137static 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
155static 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) */
163static void (*ic_cause_ipi)(int cpu) __ro_after_init;
164
165/* Use msgsndp doorbells target is a sibling, else use interrupt controller */
166static 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
174static 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
195static __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
242static 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 */
254void __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