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Linux/arch/powerpc/platforms/pseries/hotplug-cpu.c

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  1 /*
  2  * pseries CPU Hotplug infrastructure.
  3  *
  4  * Split out from arch/powerpc/platforms/pseries/setup.c
  5  *  arch/powerpc/kernel/rtas.c, and arch/powerpc/platforms/pseries/smp.c
  6  *
  7  * Peter Bergner, IBM   March 2001.
  8  * Copyright (C) 2001 IBM.
  9  * Dave Engebretsen, Peter Bergner, and
 10  * Mike Corrigan {engebret|bergner|mikec}@us.ibm.com
 11  * Plus various changes from other IBM teams...
 12  *
 13  * Copyright (C) 2006 Michael Ellerman, IBM Corporation
 14  *
 15  *      This program is free software; you can redistribute it and/or
 16  *      modify it under the terms of the GNU General Public License
 17  *      as published by the Free Software Foundation; either version
 18  *      2 of the License, or (at your option) any later version.
 19  */
 20 
 21 #include <linux/kernel.h>
 22 #include <linux/interrupt.h>
 23 #include <linux/delay.h>
 24 #include <linux/sched.h>        /* for idle_task_exit */
 25 #include <linux/cpu.h>
 26 #include <linux/of.h>
 27 #include <asm/prom.h>
 28 #include <asm/rtas.h>
 29 #include <asm/firmware.h>
 30 #include <asm/machdep.h>
 31 #include <asm/vdso_datapage.h>
 32 #include <asm/xics.h>
 33 #include <asm/plpar_wrappers.h>
 34 
 35 #include "offline_states.h"
 36 
 37 /* This version can't take the spinlock, because it never returns */
 38 static int rtas_stop_self_token = RTAS_UNKNOWN_SERVICE;
 39 
 40 static DEFINE_PER_CPU(enum cpu_state_vals, preferred_offline_state) =
 41                                                         CPU_STATE_OFFLINE;
 42 static DEFINE_PER_CPU(enum cpu_state_vals, current_state) = CPU_STATE_OFFLINE;
 43 
 44 static enum cpu_state_vals default_offline_state = CPU_STATE_OFFLINE;
 45 
 46 static int cede_offline_enabled __read_mostly = 1;
 47 
 48 /*
 49  * Enable/disable cede_offline when available.
 50  */
 51 static int __init setup_cede_offline(char *str)
 52 {
 53         if (!strcmp(str, "off"))
 54                 cede_offline_enabled = 0;
 55         else if (!strcmp(str, "on"))
 56                 cede_offline_enabled = 1;
 57         else
 58                 return 0;
 59         return 1;
 60 }
 61 
 62 __setup("cede_offline=", setup_cede_offline);
 63 
 64 enum cpu_state_vals get_cpu_current_state(int cpu)
 65 {
 66         return per_cpu(current_state, cpu);
 67 }
 68 
 69 void set_cpu_current_state(int cpu, enum cpu_state_vals state)
 70 {
 71         per_cpu(current_state, cpu) = state;
 72 }
 73 
 74 enum cpu_state_vals get_preferred_offline_state(int cpu)
 75 {
 76         return per_cpu(preferred_offline_state, cpu);
 77 }
 78 
 79 void set_preferred_offline_state(int cpu, enum cpu_state_vals state)
 80 {
 81         per_cpu(preferred_offline_state, cpu) = state;
 82 }
 83 
 84 void set_default_offline_state(int cpu)
 85 {
 86         per_cpu(preferred_offline_state, cpu) = default_offline_state;
 87 }
 88 
 89 static void rtas_stop_self(void)
 90 {
 91         static struct rtas_args args = {
 92                 .nargs = 0,
 93                 .nret = cpu_to_be32(1),
 94                 .rets = &args.args[0],
 95         };
 96 
 97         args.token = cpu_to_be32(rtas_stop_self_token);
 98 
 99         local_irq_disable();
100 
101         BUG_ON(rtas_stop_self_token == RTAS_UNKNOWN_SERVICE);
102 
103         printk("cpu %u (hwid %u) Ready to die...\n",
104                smp_processor_id(), hard_smp_processor_id());
105         enter_rtas(__pa(&args));
106 
107         panic("Alas, I survived.\n");
108 }
109 
110 static void pseries_mach_cpu_die(void)
111 {
112         unsigned int cpu = smp_processor_id();
113         unsigned int hwcpu = hard_smp_processor_id();
114         u8 cede_latency_hint = 0;
115 
116         local_irq_disable();
117         idle_task_exit();
118         xics_teardown_cpu();
119 
120         if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
121                 set_cpu_current_state(cpu, CPU_STATE_INACTIVE);
122                 if (ppc_md.suspend_disable_cpu)
123                         ppc_md.suspend_disable_cpu();
124 
125                 cede_latency_hint = 2;
126 
127                 get_lppaca()->idle = 1;
128                 if (!lppaca_shared_proc(get_lppaca()))
129                         get_lppaca()->donate_dedicated_cpu = 1;
130 
131                 while (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
132                         while (!prep_irq_for_idle()) {
133                                 local_irq_enable();
134                                 local_irq_disable();
135                         }
136 
137                         extended_cede_processor(cede_latency_hint);
138                 }
139 
140                 local_irq_disable();
141 
142                 if (!lppaca_shared_proc(get_lppaca()))
143                         get_lppaca()->donate_dedicated_cpu = 0;
144                 get_lppaca()->idle = 0;
145 
146                 if (get_preferred_offline_state(cpu) == CPU_STATE_ONLINE) {
147                         unregister_slb_shadow(hwcpu);
148 
149                         hard_irq_disable();
150                         /*
151                          * Call to start_secondary_resume() will not return.
152                          * Kernel stack will be reset and start_secondary()
153                          * will be called to continue the online operation.
154                          */
155                         start_secondary_resume();
156                 }
157         }
158 
159         /* Requested state is CPU_STATE_OFFLINE at this point */
160         WARN_ON(get_preferred_offline_state(cpu) != CPU_STATE_OFFLINE);
161 
162         set_cpu_current_state(cpu, CPU_STATE_OFFLINE);
163         unregister_slb_shadow(hwcpu);
164         rtas_stop_self();
165 
166         /* Should never get here... */
167         BUG();
168         for(;;);
169 }
170 
171 static int pseries_cpu_disable(void)
172 {
173         int cpu = smp_processor_id();
174 
175         set_cpu_online(cpu, false);
176         vdso_data->processorCount--;
177 
178         /*fix boot_cpuid here*/
179         if (cpu == boot_cpuid)
180                 boot_cpuid = cpumask_any(cpu_online_mask);
181 
182         /* FIXME: abstract this to not be platform specific later on */
183         xics_migrate_irqs_away();
184         return 0;
185 }
186 
187 /*
188  * pseries_cpu_die: Wait for the cpu to die.
189  * @cpu: logical processor id of the CPU whose death we're awaiting.
190  *
191  * This function is called from the context of the thread which is performing
192  * the cpu-offline. Here we wait for long enough to allow the cpu in question
193  * to self-destroy so that the cpu-offline thread can send the CPU_DEAD
194  * notifications.
195  *
196  * OTOH, pseries_mach_cpu_die() is called by the @cpu when it wants to
197  * self-destruct.
198  */
199 static void pseries_cpu_die(unsigned int cpu)
200 {
201         int tries;
202         int cpu_status = 1;
203         unsigned int pcpu = get_hard_smp_processor_id(cpu);
204 
205         if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
206                 cpu_status = 1;
207                 for (tries = 0; tries < 5000; tries++) {
208                         if (get_cpu_current_state(cpu) == CPU_STATE_INACTIVE) {
209                                 cpu_status = 0;
210                                 break;
211                         }
212                         msleep(1);
213                 }
214         } else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) {
215 
216                 for (tries = 0; tries < 25; tries++) {
217                         cpu_status = smp_query_cpu_stopped(pcpu);
218                         if (cpu_status == QCSS_STOPPED ||
219                             cpu_status == QCSS_HARDWARE_ERROR)
220                                 break;
221                         cpu_relax();
222                 }
223         }
224 
225         if (cpu_status != 0) {
226                 printk("Querying DEAD? cpu %i (%i) shows %i\n",
227                        cpu, pcpu, cpu_status);
228         }
229 
230         /* Isolation and deallocation are definitely done by
231          * drslot_chrp_cpu.  If they were not they would be
232          * done here.  Change isolate state to Isolate and
233          * change allocation-state to Unusable.
234          */
235         paca[cpu].cpu_start = 0;
236 }
237 
238 /*
239  * Update cpu_present_mask and paca(s) for a new cpu node.  The wrinkle
240  * here is that a cpu device node may represent up to two logical cpus
241  * in the SMT case.  We must honor the assumption in other code that
242  * the logical ids for sibling SMT threads x and y are adjacent, such
243  * that x^1 == y and y^1 == x.
244  */
245 static int pseries_add_processor(struct device_node *np)
246 {
247         unsigned int cpu;
248         cpumask_var_t candidate_mask, tmp;
249         int err = -ENOSPC, len, nthreads, i;
250         const __be32 *intserv;
251 
252         intserv = of_get_property(np, "ibm,ppc-interrupt-server#s", &len);
253         if (!intserv)
254                 return 0;
255 
256         zalloc_cpumask_var(&candidate_mask, GFP_KERNEL);
257         zalloc_cpumask_var(&tmp, GFP_KERNEL);
258 
259         nthreads = len / sizeof(u32);
260         for (i = 0; i < nthreads; i++)
261                 cpumask_set_cpu(i, tmp);
262 
263         cpu_maps_update_begin();
264 
265         BUG_ON(!cpumask_subset(cpu_present_mask, cpu_possible_mask));
266 
267         /* Get a bitmap of unoccupied slots. */
268         cpumask_xor(candidate_mask, cpu_possible_mask, cpu_present_mask);
269         if (cpumask_empty(candidate_mask)) {
270                 /* If we get here, it most likely means that NR_CPUS is
271                  * less than the partition's max processors setting.
272                  */
273                 printk(KERN_ERR "Cannot add cpu %s; this system configuration"
274                        " supports %d logical cpus.\n", np->full_name,
275                        num_possible_cpus());
276                 goto out_unlock;
277         }
278 
279         while (!cpumask_empty(tmp))
280                 if (cpumask_subset(tmp, candidate_mask))
281                         /* Found a range where we can insert the new cpu(s) */
282                         break;
283                 else
284                         cpumask_shift_left(tmp, tmp, nthreads);
285 
286         if (cpumask_empty(tmp)) {
287                 printk(KERN_ERR "Unable to find space in cpu_present_mask for"
288                        " processor %s with %d thread(s)\n", np->name,
289                        nthreads);
290                 goto out_unlock;
291         }
292 
293         for_each_cpu(cpu, tmp) {
294                 BUG_ON(cpu_present(cpu));
295                 set_cpu_present(cpu, true);
296                 set_hard_smp_processor_id(cpu, be32_to_cpu(*intserv++));
297         }
298         err = 0;
299 out_unlock:
300         cpu_maps_update_done();
301         free_cpumask_var(candidate_mask);
302         free_cpumask_var(tmp);
303         return err;
304 }
305 
306 /*
307  * Update the present map for a cpu node which is going away, and set
308  * the hard id in the paca(s) to -1 to be consistent with boot time
309  * convention for non-present cpus.
310  */
311 static void pseries_remove_processor(struct device_node *np)
312 {
313         unsigned int cpu;
314         int len, nthreads, i;
315         const __be32 *intserv;
316         u32 thread;
317 
318         intserv = of_get_property(np, "ibm,ppc-interrupt-server#s", &len);
319         if (!intserv)
320                 return;
321 
322         nthreads = len / sizeof(u32);
323 
324         cpu_maps_update_begin();
325         for (i = 0; i < nthreads; i++) {
326                 thread = be32_to_cpu(intserv[i]);
327                 for_each_present_cpu(cpu) {
328                         if (get_hard_smp_processor_id(cpu) != thread)
329                                 continue;
330                         BUG_ON(cpu_online(cpu));
331                         set_cpu_present(cpu, false);
332                         set_hard_smp_processor_id(cpu, -1);
333                         break;
334                 }
335                 if (cpu >= nr_cpu_ids)
336                         printk(KERN_WARNING "Could not find cpu to remove "
337                                "with physical id 0x%x\n", thread);
338         }
339         cpu_maps_update_done();
340 }
341 
342 static int pseries_smp_notifier(struct notifier_block *nb,
343                                 unsigned long action, void *data)
344 {
345         struct of_reconfig_data *rd = data;
346         int err = 0;
347 
348         switch (action) {
349         case OF_RECONFIG_ATTACH_NODE:
350                 err = pseries_add_processor(rd->dn);
351                 break;
352         case OF_RECONFIG_DETACH_NODE:
353                 pseries_remove_processor(rd->dn);
354                 break;
355         }
356         return notifier_from_errno(err);
357 }
358 
359 static struct notifier_block pseries_smp_nb = {
360         .notifier_call = pseries_smp_notifier,
361 };
362 
363 #define MAX_CEDE_LATENCY_LEVELS         4
364 #define CEDE_LATENCY_PARAM_LENGTH       10
365 #define CEDE_LATENCY_PARAM_MAX_LENGTH   \
366         (MAX_CEDE_LATENCY_LEVELS * CEDE_LATENCY_PARAM_LENGTH * sizeof(char))
367 #define CEDE_LATENCY_TOKEN              45
368 
369 static char cede_parameters[CEDE_LATENCY_PARAM_MAX_LENGTH];
370 
371 static int parse_cede_parameters(void)
372 {
373         memset(cede_parameters, 0, CEDE_LATENCY_PARAM_MAX_LENGTH);
374         return rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
375                          NULL,
376                          CEDE_LATENCY_TOKEN,
377                          __pa(cede_parameters),
378                          CEDE_LATENCY_PARAM_MAX_LENGTH);
379 }
380 
381 static int __init pseries_cpu_hotplug_init(void)
382 {
383         struct device_node *np;
384         const char *typep;
385         int cpu;
386         int qcss_tok;
387 
388         for_each_node_by_name(np, "interrupt-controller") {
389                 typep = of_get_property(np, "compatible", NULL);
390                 if (strstr(typep, "open-pic")) {
391                         of_node_put(np);
392 
393                         printk(KERN_INFO "CPU Hotplug not supported on "
394                                 "systems using MPIC\n");
395                         return 0;
396                 }
397         }
398 
399         rtas_stop_self_token = rtas_token("stop-self");
400         qcss_tok = rtas_token("query-cpu-stopped-state");
401 
402         if (rtas_stop_self_token == RTAS_UNKNOWN_SERVICE ||
403                         qcss_tok == RTAS_UNKNOWN_SERVICE) {
404                 printk(KERN_INFO "CPU Hotplug not supported by firmware "
405                                 "- disabling.\n");
406                 return 0;
407         }
408 
409         ppc_md.cpu_die = pseries_mach_cpu_die;
410         smp_ops->cpu_disable = pseries_cpu_disable;
411         smp_ops->cpu_die = pseries_cpu_die;
412 
413         /* Processors can be added/removed only on LPAR */
414         if (firmware_has_feature(FW_FEATURE_LPAR)) {
415                 of_reconfig_notifier_register(&pseries_smp_nb);
416                 cpu_maps_update_begin();
417                 if (cede_offline_enabled && parse_cede_parameters() == 0) {
418                         default_offline_state = CPU_STATE_INACTIVE;
419                         for_each_online_cpu(cpu)
420                                 set_default_offline_state(cpu);
421                 }
422                 cpu_maps_update_done();
423         }
424 
425         return 0;
426 }
427 machine_arch_initcall(pseries, pseries_cpu_hotplug_init);
428 

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