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 */ 53 static cpumask_var_t of_spin_mask; 54 55 /* Query where a cpu is now. Return codes #defined in plpar_wrappers.h */ 56 int 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 */ 88 static 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 /* Fixup atomic count: it exited inside IRQ handler. */ 109 task_thread_info(paca_ptrs[lcpu]->__current)->preempt_count = 0; 110 111 /* 112 * If the RTAS start-cpu token does not exist then presume the 113 * cpu is already spinning. 114 */ 115 start_cpu = rtas_token("start-cpu"); 116 if (start_cpu == RTAS_UNKNOWN_SERVICE) 117 return 1; 118 119 status = rtas_call(start_cpu, 3, 1, NULL, pcpu, start_here, pcpu); 120 if (status != 0) { 121 printk(KERN_ERR "start-cpu failed: %i\n", status); 122 return 0; 123 } 124 125 return 1; 126 } 127 128 static void smp_setup_cpu(int cpu) 129 { 130 if (xive_enabled()) 131 xive_smp_setup_cpu(); 132 else if (cpu != boot_cpuid) 133 xics_setup_cpu(); 134 135 if (firmware_has_feature(FW_FEATURE_SPLPAR)) 136 vpa_init(cpu); 137 138 cpumask_clear_cpu(cpu, of_spin_mask); 139 } 140 141 static int smp_pSeries_kick_cpu(int nr) 142 { 143 if (nr < 0 || nr >= nr_cpu_ids) 144 return -EINVAL; 145 146 if (!smp_startup_cpu(nr)) 147 return -ENOENT; 148 149 /* 150 * The processor is currently spinning, waiting for the 151 * cpu_start field to become non-zero After we set cpu_start, 152 * the processor will continue on to secondary_start 153 */ 154 paca_ptrs[nr]->cpu_start = 1; 155 156 return 0; 157 } 158 159 static int pseries_smp_prepare_cpu(int cpu) 160 { 161 if (xive_enabled()) 162 return xive_smp_prepare_cpu(cpu); 163 return 0; 164 } 165 166 /* Cause IPI as setup by the interrupt controller (xics or xive) */ 167 static void (*ic_cause_ipi)(int cpu) __ro_after_init; 168 169 /* Use msgsndp doorbells target is a sibling, else use interrupt controller */ 170 static void dbell_or_ic_cause_ipi(int cpu) 171 { 172 if (doorbell_try_core_ipi(cpu)) 173 return; 174 175 ic_cause_ipi(cpu); 176 } 177 178 static int pseries_cause_nmi_ipi(int cpu) 179 { 180 int hwcpu; 181 182 if (cpu == NMI_IPI_ALL_OTHERS) { 183 hwcpu = H_SIGNAL_SYS_RESET_ALL_OTHERS; 184 } else { 185 if (cpu < 0) { 186 WARN_ONCE(true, "incorrect cpu parameter %d", cpu); 187 return 0; 188 } 189 190 hwcpu = get_hard_smp_processor_id(cpu); 191 } 192 193 if (plpar_signal_sys_reset(hwcpu) == H_SUCCESS) 194 return 1; 195 196 return 0; 197 } 198 199 static __init void pSeries_smp_probe(void) 200 { 201 if (xive_enabled()) 202 xive_smp_probe(); 203 else 204 xics_smp_probe(); 205 206 /* No doorbell facility, must use the interrupt controller for IPIs */ 207 if (!cpu_has_feature(CPU_FTR_DBELL)) 208 return; 209 210 /* Doorbells can only be used for IPIs between SMT siblings */ 211 if (!cpu_has_feature(CPU_FTR_SMT)) 212 return; 213 214 if (check_kvm_guest()) { 215 /* 216 * KVM emulates doorbells by disabling FSCR[MSGP] so msgsndp 217 * faults to the hypervisor which then reads the instruction 218 * from guest memory, which tends to be slower than using XIVE. 219 */ 220 if (xive_enabled()) 221 return; 222 223 /* 224 * XICS hcalls aren't as fast, so we can use msgsndp (which 225 * also helps exercise KVM emulation), however KVM can't 226 * emulate secure guests because it can't read the instruction 227 * out of their memory. 228 */ 229 if (is_secure_guest()) 230 return; 231 } 232 233 /* 234 * Under PowerVM, FSCR[MSGP] is enabled as guest vCPU siblings are 235 * gang scheduled on the same physical core, so doorbells are always 236 * faster than the interrupt controller, and they can be used by 237 * secure guests. 238 */ 239 240 ic_cause_ipi = smp_ops->cause_ipi; 241 smp_ops->cause_ipi = dbell_or_ic_cause_ipi; 242 } 243 244 static struct smp_ops_t pseries_smp_ops = { 245 .message_pass = NULL, /* Use smp_muxed_ipi_message_pass */ 246 .cause_ipi = NULL, /* Filled at runtime by pSeries_smp_probe() */ 247 .cause_nmi_ipi = pseries_cause_nmi_ipi, 248 .probe = pSeries_smp_probe, 249 .prepare_cpu = pseries_smp_prepare_cpu, 250 .kick_cpu = smp_pSeries_kick_cpu, 251 .setup_cpu = smp_setup_cpu, 252 .cpu_bootable = smp_generic_cpu_bootable, 253 }; 254 255 /* This is called very early */ 256 void __init smp_init_pseries(void) 257 { 258 int i; 259 260 pr_debug(" -> smp_init_pSeries()\n"); 261 smp_ops = &pseries_smp_ops; 262 263 alloc_bootmem_cpumask_var(&of_spin_mask); 264 265 /* 266 * Mark threads which are still spinning in hold loops 267 * 268 * We know prom_init will not have started them if RTAS supports 269 * query-cpu-stopped-state. 270 */ 271 if (rtas_token("query-cpu-stopped-state") == RTAS_UNKNOWN_SERVICE) { 272 if (cpu_has_feature(CPU_FTR_SMT)) { 273 for_each_present_cpu(i) { 274 if (cpu_thread_in_core(i) == 0) 275 cpumask_set_cpu(i, of_spin_mask); 276 } 277 } else 278 cpumask_copy(of_spin_mask, cpu_present_mask); 279 280 cpumask_clear_cpu(boot_cpuid, of_spin_mask); 281 } 282 283 /* Non-lpar has additional take/give timebase */ 284 if (rtas_token("freeze-time-base") != RTAS_UNKNOWN_SERVICE) { 285 smp_ops->give_timebase = rtas_give_timebase; 286 smp_ops->take_timebase = rtas_take_timebase; 287 } 288 289 pr_debug(" <- smp_init_pSeries()\n"); 290 } 291