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