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1 /*
2  * Xen SMP support
3  *
4  * This file implements the Xen versions of smp_ops.  SMP under Xen is
5  * very straightforward.  Bringing a CPU up is simply a matter of
6  * loading its initial context and setting it running.
7  *
8  * IPIs are handled through the Xen event mechanism.
9  *
10  * Because virtual CPUs can be scheduled onto any real CPU, there's no
11  * useful topology information for the kernel to make use of.  As a
12  * result, all CPUs are treated as if they're single-core and
13  * single-threaded.
14  */
15 #include <linux/sched.h>
16 #include <linux/err.h>
17 #include <linux/smp.h>
18 
19 #include <asm/paravirt.h>
20 #include <asm/desc.h>
21 #include <asm/pgtable.h>
22 #include <asm/cpu.h>
23 
24 #include <xen/interface/xen.h>
25 #include <xen/interface/vcpu.h>
26 
27 #include <asm/xen/interface.h>
28 #include <asm/xen/hypercall.h>
29 
30 #include <xen/page.h>
31 #include <xen/events.h>
32 
33 #include "xen-ops.h"
34 #include "mmu.h"
35 
36 cpumask_var_t xen_cpu_initialized_map;
37 
38 static DEFINE_PER_CPU(int, resched_irq);
39 static DEFINE_PER_CPU(int, callfunc_irq);
40 static DEFINE_PER_CPU(int, callfuncsingle_irq);
41 static DEFINE_PER_CPU(int, debug_irq) = -1;
42 
43 static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id);
44 static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id);
45 
46 /*
47  * Reschedule call back. Nothing to do,
48  * all the work is done automatically when
49  * we return from the interrupt.
50  */
xen_reschedule_interrupt(int irq,void * dev_id)51 static irqreturn_t xen_reschedule_interrupt(int irq, void *dev_id)
52 {
53 #ifdef CONFIG_X86_32
54 	__get_cpu_var(irq_stat).irq_resched_count++;
55 #else
56 	add_pda(irq_resched_count, 1);
57 #endif
58 
59 	return IRQ_HANDLED;
60 }
61 
cpu_bringup(void)62 static __cpuinit void cpu_bringup(void)
63 {
64 	int cpu = smp_processor_id();
65 
66 	cpu_init();
67 	touch_softlockup_watchdog();
68 	preempt_disable();
69 
70 	xen_enable_sysenter();
71 	xen_enable_syscall();
72 
73 	cpu = smp_processor_id();
74 	smp_store_cpu_info(cpu);
75 	cpu_data(cpu).x86_max_cores = 1;
76 	set_cpu_sibling_map(cpu);
77 
78 	xen_setup_cpu_clockevents();
79 
80 	cpu_set(cpu, cpu_online_map);
81 	x86_write_percpu(cpu_state, CPU_ONLINE);
82 	wmb();
83 
84 	/* We can take interrupts now: we're officially "up". */
85 	local_irq_enable();
86 
87 	wmb();			/* make sure everything is out */
88 }
89 
cpu_bringup_and_idle(void)90 static __cpuinit void cpu_bringup_and_idle(void)
91 {
92 	cpu_bringup();
93 	cpu_idle();
94 }
95 
xen_smp_intr_init(unsigned int cpu)96 static int xen_smp_intr_init(unsigned int cpu)
97 {
98 	int rc;
99 	const char *resched_name, *callfunc_name, *debug_name;
100 
101 	resched_name = kasprintf(GFP_KERNEL, "resched%d", cpu);
102 	rc = bind_ipi_to_irqhandler(XEN_RESCHEDULE_VECTOR,
103 				    cpu,
104 				    xen_reschedule_interrupt,
105 				    IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
106 				    resched_name,
107 				    NULL);
108 	if (rc < 0)
109 		goto fail;
110 	per_cpu(resched_irq, cpu) = rc;
111 
112 	callfunc_name = kasprintf(GFP_KERNEL, "callfunc%d", cpu);
113 	rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_VECTOR,
114 				    cpu,
115 				    xen_call_function_interrupt,
116 				    IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
117 				    callfunc_name,
118 				    NULL);
119 	if (rc < 0)
120 		goto fail;
121 	per_cpu(callfunc_irq, cpu) = rc;
122 
123 	debug_name = kasprintf(GFP_KERNEL, "debug%d", cpu);
124 	rc = bind_virq_to_irqhandler(VIRQ_DEBUG, cpu, xen_debug_interrupt,
125 				     IRQF_DISABLED | IRQF_PERCPU | IRQF_NOBALANCING,
126 				     debug_name, NULL);
127 	if (rc < 0)
128 		goto fail;
129 	per_cpu(debug_irq, cpu) = rc;
130 
131 	callfunc_name = kasprintf(GFP_KERNEL, "callfuncsingle%d", cpu);
132 	rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_SINGLE_VECTOR,
133 				    cpu,
134 				    xen_call_function_single_interrupt,
135 				    IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
136 				    callfunc_name,
137 				    NULL);
138 	if (rc < 0)
139 		goto fail;
140 	per_cpu(callfuncsingle_irq, cpu) = rc;
141 
142 	return 0;
143 
144  fail:
145 	if (per_cpu(resched_irq, cpu) >= 0)
146 		unbind_from_irqhandler(per_cpu(resched_irq, cpu), NULL);
147 	if (per_cpu(callfunc_irq, cpu) >= 0)
148 		unbind_from_irqhandler(per_cpu(callfunc_irq, cpu), NULL);
149 	if (per_cpu(debug_irq, cpu) >= 0)
150 		unbind_from_irqhandler(per_cpu(debug_irq, cpu), NULL);
151 	if (per_cpu(callfuncsingle_irq, cpu) >= 0)
152 		unbind_from_irqhandler(per_cpu(callfuncsingle_irq, cpu), NULL);
153 
154 	return rc;
155 }
156 
xen_fill_possible_map(void)157 static void __init xen_fill_possible_map(void)
158 {
159 	int i, rc;
160 
161 	for (i = 0; i < nr_cpu_ids; i++) {
162 		rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
163 		if (rc >= 0) {
164 			num_processors++;
165 			cpu_set(i, cpu_possible_map);
166 		}
167 	}
168 }
169 
xen_smp_prepare_boot_cpu(void)170 static void __init xen_smp_prepare_boot_cpu(void)
171 {
172 	BUG_ON(smp_processor_id() != 0);
173 	native_smp_prepare_boot_cpu();
174 
175 	/* We've switched to the "real" per-cpu gdt, so make sure the
176 	   old memory can be recycled */
177 	make_lowmem_page_readwrite(&per_cpu_var(gdt_page));
178 
179 	xen_setup_vcpu_info_placement();
180 }
181 
xen_smp_prepare_cpus(unsigned int max_cpus)182 static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
183 {
184 	unsigned cpu;
185 
186 	xen_init_lock_cpu(0);
187 
188 	smp_store_cpu_info(0);
189 	cpu_data(0).x86_max_cores = 1;
190 	set_cpu_sibling_map(0);
191 
192 	if (xen_smp_intr_init(0))
193 		BUG();
194 
195 	if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
196 		panic("could not allocate xen_cpu_initialized_map\n");
197 
198 	cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
199 
200 	/* Restrict the possible_map according to max_cpus. */
201 	while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
202 		for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
203 			continue;
204 		cpu_clear(cpu, cpu_possible_map);
205 	}
206 
207 	for_each_possible_cpu (cpu) {
208 		struct task_struct *idle;
209 
210 		if (cpu == 0)
211 			continue;
212 
213 		idle = fork_idle(cpu);
214 		if (IS_ERR(idle))
215 			panic("failed fork for CPU %d", cpu);
216 
217 		cpu_set(cpu, cpu_present_map);
218 	}
219 }
220 
221 static __cpuinit int
cpu_initialize_context(unsigned int cpu,struct task_struct * idle)222 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
223 {
224 	struct vcpu_guest_context *ctxt;
225 	struct desc_struct *gdt;
226 
227 	if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
228 		return 0;
229 
230 	ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
231 	if (ctxt == NULL)
232 		return -ENOMEM;
233 
234 	gdt = get_cpu_gdt_table(cpu);
235 
236 	ctxt->flags = VGCF_IN_KERNEL;
237 	ctxt->user_regs.ds = __USER_DS;
238 	ctxt->user_regs.es = __USER_DS;
239 	ctxt->user_regs.ss = __KERNEL_DS;
240 #ifdef CONFIG_X86_32
241 	ctxt->user_regs.fs = __KERNEL_PERCPU;
242 #endif
243 	ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
244 	ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
245 
246 	memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
247 
248 	xen_copy_trap_info(ctxt->trap_ctxt);
249 
250 	ctxt->ldt_ents = 0;
251 
252 	BUG_ON((unsigned long)gdt & ~PAGE_MASK);
253 	make_lowmem_page_readonly(gdt);
254 
255 	ctxt->gdt_frames[0] = virt_to_mfn(gdt);
256 	ctxt->gdt_ents      = GDT_ENTRIES;
257 
258 	ctxt->user_regs.cs = __KERNEL_CS;
259 	ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);
260 
261 	ctxt->kernel_ss = __KERNEL_DS;
262 	ctxt->kernel_sp = idle->thread.sp0;
263 
264 #ifdef CONFIG_X86_32
265 	ctxt->event_callback_cs     = __KERNEL_CS;
266 	ctxt->failsafe_callback_cs  = __KERNEL_CS;
267 #endif
268 	ctxt->event_callback_eip    = (unsigned long)xen_hypervisor_callback;
269 	ctxt->failsafe_callback_eip = (unsigned long)xen_failsafe_callback;
270 
271 	per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
272 	ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
273 
274 	if (HYPERVISOR_vcpu_op(VCPUOP_initialise, cpu, ctxt))
275 		BUG();
276 
277 	kfree(ctxt);
278 	return 0;
279 }
280 
xen_cpu_up(unsigned int cpu)281 static int __cpuinit xen_cpu_up(unsigned int cpu)
282 {
283 	struct task_struct *idle = idle_task(cpu);
284 	int rc;
285 
286 #ifdef CONFIG_X86_64
287 	/* Allocate node local memory for AP pdas */
288 	WARN_ON(cpu == 0);
289 	if (cpu > 0) {
290 		rc = get_local_pda(cpu);
291 		if (rc)
292 			return rc;
293 	}
294 #endif
295 
296 #ifdef CONFIG_X86_32
297 	init_gdt(cpu);
298 	per_cpu(current_task, cpu) = idle;
299 	irq_ctx_init(cpu);
300 #else
301 	cpu_pda(cpu)->pcurrent = idle;
302 	clear_tsk_thread_flag(idle, TIF_FORK);
303 #endif
304 	xen_setup_timer(cpu);
305 	xen_init_lock_cpu(cpu);
306 
307 	per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
308 
309 	/* make sure interrupts start blocked */
310 	per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
311 
312 	rc = cpu_initialize_context(cpu, idle);
313 	if (rc)
314 		return rc;
315 
316 	if (num_online_cpus() == 1)
317 		alternatives_smp_switch(1);
318 
319 	rc = xen_smp_intr_init(cpu);
320 	if (rc)
321 		return rc;
322 
323 	rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
324 	BUG_ON(rc);
325 
326 	while(per_cpu(cpu_state, cpu) != CPU_ONLINE) {
327 		HYPERVISOR_sched_op(SCHEDOP_yield, 0);
328 		barrier();
329 	}
330 
331 	return 0;
332 }
333 
xen_smp_cpus_done(unsigned int max_cpus)334 static void xen_smp_cpus_done(unsigned int max_cpus)
335 {
336 }
337 
338 #ifdef CONFIG_HOTPLUG_CPU
xen_cpu_disable(void)339 static int xen_cpu_disable(void)
340 {
341 	unsigned int cpu = smp_processor_id();
342 	if (cpu == 0)
343 		return -EBUSY;
344 
345 	cpu_disable_common();
346 
347 	load_cr3(swapper_pg_dir);
348 	return 0;
349 }
350 
xen_cpu_die(unsigned int cpu)351 static void xen_cpu_die(unsigned int cpu)
352 {
353 	while (HYPERVISOR_vcpu_op(VCPUOP_is_up, cpu, NULL)) {
354 		current->state = TASK_UNINTERRUPTIBLE;
355 		schedule_timeout(HZ/10);
356 	}
357 	unbind_from_irqhandler(per_cpu(resched_irq, cpu), NULL);
358 	unbind_from_irqhandler(per_cpu(callfunc_irq, cpu), NULL);
359 	unbind_from_irqhandler(per_cpu(debug_irq, cpu), NULL);
360 	unbind_from_irqhandler(per_cpu(callfuncsingle_irq, cpu), NULL);
361 	xen_uninit_lock_cpu(cpu);
362 	xen_teardown_timer(cpu);
363 
364 	if (num_online_cpus() == 1)
365 		alternatives_smp_switch(0);
366 }
367 
xen_play_dead(void)368 static void __cpuinit xen_play_dead(void) /* used only with CPU_HOTPLUG */
369 {
370 	play_dead_common();
371 	HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
372 	cpu_bringup();
373 }
374 
375 #else /* !CONFIG_HOTPLUG_CPU */
xen_cpu_disable(void)376 static int xen_cpu_disable(void)
377 {
378 	return -ENOSYS;
379 }
380 
xen_cpu_die(unsigned int cpu)381 static void xen_cpu_die(unsigned int cpu)
382 {
383 	BUG();
384 }
385 
xen_play_dead(void)386 static void xen_play_dead(void)
387 {
388 	BUG();
389 }
390 
391 #endif
stop_self(void * v)392 static void stop_self(void *v)
393 {
394 	int cpu = smp_processor_id();
395 
396 	/* make sure we're not pinning something down */
397 	load_cr3(swapper_pg_dir);
398 	/* should set up a minimal gdt */
399 
400 	HYPERVISOR_vcpu_op(VCPUOP_down, cpu, NULL);
401 	BUG();
402 }
403 
xen_smp_send_stop(void)404 static void xen_smp_send_stop(void)
405 {
406 	smp_call_function(stop_self, NULL, 0);
407 }
408 
xen_smp_send_reschedule(int cpu)409 static void xen_smp_send_reschedule(int cpu)
410 {
411 	xen_send_IPI_one(cpu, XEN_RESCHEDULE_VECTOR);
412 }
413 
xen_send_IPI_mask(const struct cpumask * mask,enum ipi_vector vector)414 static void xen_send_IPI_mask(const struct cpumask *mask,
415 			      enum ipi_vector vector)
416 {
417 	unsigned cpu;
418 
419 	for_each_cpu_and(cpu, mask, cpu_online_mask)
420 		xen_send_IPI_one(cpu, vector);
421 }
422 
xen_smp_send_call_function_ipi(const struct cpumask * mask)423 static void xen_smp_send_call_function_ipi(const struct cpumask *mask)
424 {
425 	int cpu;
426 
427 	xen_send_IPI_mask(mask, XEN_CALL_FUNCTION_VECTOR);
428 
429 	/* Make sure other vcpus get a chance to run if they need to. */
430 	for_each_cpu(cpu, mask) {
431 		if (xen_vcpu_stolen(cpu)) {
432 			HYPERVISOR_sched_op(SCHEDOP_yield, 0);
433 			break;
434 		}
435 	}
436 }
437 
xen_smp_send_call_function_single_ipi(int cpu)438 static void xen_smp_send_call_function_single_ipi(int cpu)
439 {
440 	xen_send_IPI_mask(cpumask_of(cpu),
441 			  XEN_CALL_FUNCTION_SINGLE_VECTOR);
442 }
443 
xen_call_function_interrupt(int irq,void * dev_id)444 static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id)
445 {
446 	irq_enter();
447 	generic_smp_call_function_interrupt();
448 #ifdef CONFIG_X86_32
449 	__get_cpu_var(irq_stat).irq_call_count++;
450 #else
451 	add_pda(irq_call_count, 1);
452 #endif
453 	irq_exit();
454 
455 	return IRQ_HANDLED;
456 }
457 
xen_call_function_single_interrupt(int irq,void * dev_id)458 static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id)
459 {
460 	irq_enter();
461 	generic_smp_call_function_single_interrupt();
462 #ifdef CONFIG_X86_32
463 	__get_cpu_var(irq_stat).irq_call_count++;
464 #else
465 	add_pda(irq_call_count, 1);
466 #endif
467 	irq_exit();
468 
469 	return IRQ_HANDLED;
470 }
471 
472 static const struct smp_ops xen_smp_ops __initdata = {
473 	.smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu,
474 	.smp_prepare_cpus = xen_smp_prepare_cpus,
475 	.smp_cpus_done = xen_smp_cpus_done,
476 
477 	.cpu_up = xen_cpu_up,
478 	.cpu_die = xen_cpu_die,
479 	.cpu_disable = xen_cpu_disable,
480 	.play_dead = xen_play_dead,
481 
482 	.smp_send_stop = xen_smp_send_stop,
483 	.smp_send_reschedule = xen_smp_send_reschedule,
484 
485 	.send_call_func_ipi = xen_smp_send_call_function_ipi,
486 	.send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
487 };
488 
xen_smp_init(void)489 void __init xen_smp_init(void)
490 {
491 	smp_ops = xen_smp_ops;
492 	xen_fill_possible_map();
493 	xen_init_spinlocks();
494 }
495