xref: /openbmc/linux/arch/x86/xen/smp_pv.c (revision fe3e0a13e597c1c8617814bf9b42ab732db5c26e)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Xen SMP support
4  *
5  * This file implements the Xen versions of smp_ops.  SMP under Xen is
6  * very straightforward.  Bringing a CPU up is simply a matter of
7  * loading its initial context and setting it running.
8  *
9  * IPIs are handled through the Xen event mechanism.
10  *
11  * Because virtual CPUs can be scheduled onto any real CPU, there's no
12  * useful topology information for the kernel to make use of.  As a
13  * result, all CPUs are treated as if they're single-core and
14  * single-threaded.
15  */
16 #include <linux/sched.h>
17 #include <linux/sched/task_stack.h>
18 #include <linux/err.h>
19 #include <linux/slab.h>
20 #include <linux/smp.h>
21 #include <linux/irq_work.h>
22 #include <linux/tick.h>
23 #include <linux/nmi.h>
24 #include <linux/cpuhotplug.h>
25 #include <linux/stackprotector.h>
26 #include <linux/pgtable.h>
27 
28 #include <asm/paravirt.h>
29 #include <asm/idtentry.h>
30 #include <asm/desc.h>
31 #include <asm/cpu.h>
32 #include <asm/io_apic.h>
33 
34 #include <xen/interface/xen.h>
35 #include <xen/interface/vcpu.h>
36 #include <xen/interface/xenpmu.h>
37 
38 #include <asm/spec-ctrl.h>
39 #include <asm/xen/interface.h>
40 #include <asm/xen/hypercall.h>
41 
42 #include <xen/xen.h>
43 #include <xen/page.h>
44 #include <xen/events.h>
45 
46 #include <xen/hvc-console.h>
47 #include "xen-ops.h"
48 #include "mmu.h"
49 #include "smp.h"
50 #include "pmu.h"
51 
52 cpumask_var_t xen_cpu_initialized_map;
53 
54 static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
55 static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
56 
57 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
58 void asm_cpu_bringup_and_idle(void);
59 
60 static void cpu_bringup(void)
61 {
62 	int cpu;
63 
64 	cr4_init();
65 	cpu_init();
66 	fpu__init_cpu();
67 	touch_softlockup_watchdog();
68 
69 	/* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
70 	if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
71 		xen_enable_sysenter();
72 		xen_enable_syscall();
73 	}
74 	cpu = smp_processor_id();
75 	smp_store_cpu_info(cpu);
76 	cpu_data(cpu).x86_max_cores = 1;
77 	set_cpu_sibling_map(cpu);
78 
79 	speculative_store_bypass_ht_init();
80 
81 	xen_setup_cpu_clockevents();
82 
83 	notify_cpu_starting(cpu);
84 
85 	set_cpu_online(cpu, true);
86 
87 	cpu_set_state_online(cpu);  /* Implies full memory barrier. */
88 
89 	/* We can take interrupts now: we're officially "up". */
90 	local_irq_enable();
91 }
92 
93 asmlinkage __visible void cpu_bringup_and_idle(void)
94 {
95 	cpu_bringup();
96 	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
97 }
98 
99 void xen_smp_intr_free_pv(unsigned int cpu)
100 {
101 	kfree(per_cpu(xen_irq_work, cpu).name);
102 	per_cpu(xen_irq_work, cpu).name = NULL;
103 	if (per_cpu(xen_irq_work, cpu).irq >= 0) {
104 		unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
105 		per_cpu(xen_irq_work, cpu).irq = -1;
106 	}
107 
108 	kfree(per_cpu(xen_pmu_irq, cpu).name);
109 	per_cpu(xen_pmu_irq, cpu).name = NULL;
110 	if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
111 		unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
112 		per_cpu(xen_pmu_irq, cpu).irq = -1;
113 	}
114 }
115 
116 int xen_smp_intr_init_pv(unsigned int cpu)
117 {
118 	int rc;
119 	char *callfunc_name, *pmu_name;
120 
121 	callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
122 	per_cpu(xen_irq_work, cpu).name = callfunc_name;
123 	rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
124 				    cpu,
125 				    xen_irq_work_interrupt,
126 				    IRQF_PERCPU|IRQF_NOBALANCING,
127 				    callfunc_name,
128 				    NULL);
129 	if (rc < 0)
130 		goto fail;
131 	per_cpu(xen_irq_work, cpu).irq = rc;
132 
133 	if (is_xen_pmu) {
134 		pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
135 		per_cpu(xen_pmu_irq, cpu).name = pmu_name;
136 		rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
137 					     xen_pmu_irq_handler,
138 					     IRQF_PERCPU|IRQF_NOBALANCING,
139 					     pmu_name, NULL);
140 		if (rc < 0)
141 			goto fail;
142 		per_cpu(xen_pmu_irq, cpu).irq = rc;
143 	}
144 
145 	return 0;
146 
147  fail:
148 	xen_smp_intr_free_pv(cpu);
149 	return rc;
150 }
151 
152 static void __init _get_smp_config(unsigned int early)
153 {
154 	int i, rc;
155 	unsigned int subtract = 0;
156 
157 	if (early)
158 		return;
159 
160 	num_processors = 0;
161 	disabled_cpus = 0;
162 	for (i = 0; i < nr_cpu_ids; i++) {
163 		rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
164 		if (rc >= 0) {
165 			num_processors++;
166 			set_cpu_possible(i, true);
167 		} else {
168 			set_cpu_possible(i, false);
169 			set_cpu_present(i, false);
170 			subtract++;
171 		}
172 	}
173 #ifdef CONFIG_HOTPLUG_CPU
174 	/* This is akin to using 'nr_cpus' on the Linux command line.
175 	 * Which is OK as when we use 'dom0_max_vcpus=X' we can only
176 	 * have up to X, while nr_cpu_ids is greater than X. This
177 	 * normally is not a problem, except when CPU hotplugging
178 	 * is involved and then there might be more than X CPUs
179 	 * in the guest - which will not work as there is no
180 	 * hypercall to expand the max number of VCPUs an already
181 	 * running guest has. So cap it up to X. */
182 	if (subtract)
183 		set_nr_cpu_ids(nr_cpu_ids - subtract);
184 #endif
185 
186 }
187 
188 static void __init xen_pv_smp_prepare_boot_cpu(void)
189 {
190 	BUG_ON(smp_processor_id() != 0);
191 	native_smp_prepare_boot_cpu();
192 
193 	if (!xen_feature(XENFEAT_writable_page_tables))
194 		/* We've switched to the "real" per-cpu gdt, so make
195 		 * sure the old memory can be recycled. */
196 		make_lowmem_page_readwrite(xen_initial_gdt);
197 
198 	xen_setup_vcpu_info_placement();
199 
200 	/*
201 	 * The alternative logic (which patches the unlock/lock) runs before
202 	 * the smp bootup up code is activated. Hence we need to set this up
203 	 * the core kernel is being patched. Otherwise we will have only
204 	 * modules patched but not core code.
205 	 */
206 	xen_init_spinlocks();
207 }
208 
209 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
210 {
211 	unsigned cpu;
212 
213 	if (skip_ioapic_setup) {
214 		char *m = (max_cpus == 0) ?
215 			"The nosmp parameter is incompatible with Xen; " \
216 			"use Xen dom0_max_vcpus=1 parameter" :
217 			"The noapic parameter is incompatible with Xen";
218 
219 		xen_raw_printk(m);
220 		panic(m);
221 	}
222 	xen_init_lock_cpu(0);
223 
224 	smp_prepare_cpus_common();
225 
226 	cpu_data(0).x86_max_cores = 1;
227 
228 	speculative_store_bypass_ht_init();
229 
230 	xen_pmu_init(0);
231 
232 	if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
233 		BUG();
234 
235 	if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
236 		panic("could not allocate xen_cpu_initialized_map\n");
237 
238 	cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
239 
240 	/* Restrict the possible_map according to max_cpus. */
241 	while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
242 		for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
243 			continue;
244 		set_cpu_possible(cpu, false);
245 	}
246 
247 	for_each_possible_cpu(cpu)
248 		set_cpu_present(cpu, true);
249 }
250 
251 static int
252 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
253 {
254 	struct vcpu_guest_context *ctxt;
255 	struct desc_struct *gdt;
256 	unsigned long gdt_mfn;
257 
258 	/* used to tell cpu_init() that it can proceed with initialization */
259 	cpumask_set_cpu(cpu, cpu_callout_mask);
260 	if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
261 		return 0;
262 
263 	ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
264 	if (ctxt == NULL) {
265 		cpumask_clear_cpu(cpu, xen_cpu_initialized_map);
266 		cpumask_clear_cpu(cpu, cpu_callout_mask);
267 		return -ENOMEM;
268 	}
269 
270 	gdt = get_cpu_gdt_rw(cpu);
271 
272 	/*
273 	 * Bring up the CPU in cpu_bringup_and_idle() with the stack
274 	 * pointing just below where pt_regs would be if it were a normal
275 	 * kernel entry.
276 	 */
277 	ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle;
278 	ctxt->flags = VGCF_IN_KERNEL;
279 	ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
280 	ctxt->user_regs.ds = __USER_DS;
281 	ctxt->user_regs.es = __USER_DS;
282 	ctxt->user_regs.ss = __KERNEL_DS;
283 	ctxt->user_regs.cs = __KERNEL_CS;
284 	ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
285 
286 	xen_copy_trap_info(ctxt->trap_ctxt);
287 
288 	BUG_ON((unsigned long)gdt & ~PAGE_MASK);
289 
290 	gdt_mfn = arbitrary_virt_to_mfn(gdt);
291 	make_lowmem_page_readonly(gdt);
292 	make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
293 
294 	ctxt->gdt_frames[0] = gdt_mfn;
295 	ctxt->gdt_ents      = GDT_ENTRIES;
296 
297 	/*
298 	 * Set SS:SP that Xen will use when entering guest kernel mode
299 	 * from guest user mode.  Subsequent calls to load_sp0() can
300 	 * change this value.
301 	 */
302 	ctxt->kernel_ss = __KERNEL_DS;
303 	ctxt->kernel_sp = task_top_of_stack(idle);
304 
305 	ctxt->gs_base_kernel = per_cpu_offset(cpu);
306 	ctxt->event_callback_eip    =
307 		(unsigned long)xen_asm_exc_xen_hypervisor_callback;
308 	ctxt->failsafe_callback_eip =
309 		(unsigned long)xen_failsafe_callback;
310 	per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
311 
312 	ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
313 	if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
314 		BUG();
315 
316 	kfree(ctxt);
317 	return 0;
318 }
319 
320 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
321 {
322 	int rc;
323 
324 	rc = common_cpu_up(cpu, idle);
325 	if (rc)
326 		return rc;
327 
328 	xen_setup_runstate_info(cpu);
329 
330 	/*
331 	 * PV VCPUs are always successfully taken down (see 'while' loop
332 	 * in xen_cpu_die()), so -EBUSY is an error.
333 	 */
334 	rc = cpu_check_up_prepare(cpu);
335 	if (rc)
336 		return rc;
337 
338 	/* make sure interrupts start blocked */
339 	per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
340 
341 	rc = cpu_initialize_context(cpu, idle);
342 	if (rc)
343 		return rc;
344 
345 	xen_pmu_init(cpu);
346 
347 	rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
348 	BUG_ON(rc);
349 
350 	while (cpu_report_state(cpu) != CPU_ONLINE)
351 		HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
352 
353 	return 0;
354 }
355 
356 #ifdef CONFIG_HOTPLUG_CPU
357 static int xen_pv_cpu_disable(void)
358 {
359 	unsigned int cpu = smp_processor_id();
360 	if (cpu == 0)
361 		return -EBUSY;
362 
363 	cpu_disable_common();
364 
365 	load_cr3(swapper_pg_dir);
366 	return 0;
367 }
368 
369 static void xen_pv_cpu_die(unsigned int cpu)
370 {
371 	while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
372 				  xen_vcpu_nr(cpu), NULL)) {
373 		__set_current_state(TASK_UNINTERRUPTIBLE);
374 		schedule_timeout(HZ/10);
375 	}
376 
377 	if (common_cpu_die(cpu) == 0) {
378 		xen_smp_intr_free(cpu);
379 		xen_uninit_lock_cpu(cpu);
380 		xen_teardown_timer(cpu);
381 		xen_pmu_finish(cpu);
382 	}
383 }
384 
385 static void __noreturn xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
386 {
387 	play_dead_common();
388 	HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
389 	xen_cpu_bringup_again((unsigned long)task_pt_regs(current));
390 	BUG();
391 }
392 
393 #else /* !CONFIG_HOTPLUG_CPU */
394 static int xen_pv_cpu_disable(void)
395 {
396 	return -ENOSYS;
397 }
398 
399 static void xen_pv_cpu_die(unsigned int cpu)
400 {
401 	BUG();
402 }
403 
404 static void __noreturn xen_pv_play_dead(void)
405 {
406 	BUG();
407 }
408 
409 #endif
410 static void stop_self(void *v)
411 {
412 	int cpu = smp_processor_id();
413 
414 	/* make sure we're not pinning something down */
415 	load_cr3(swapper_pg_dir);
416 	/* should set up a minimal gdt */
417 
418 	set_cpu_online(cpu, false);
419 
420 	HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
421 	BUG();
422 }
423 
424 static void xen_pv_stop_other_cpus(int wait)
425 {
426 	smp_call_function(stop_self, NULL, wait);
427 }
428 
429 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
430 {
431 	irq_work_run();
432 	inc_irq_stat(apic_irq_work_irqs);
433 
434 	return IRQ_HANDLED;
435 }
436 
437 static const struct smp_ops xen_smp_ops __initconst = {
438 	.smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
439 	.smp_prepare_cpus = xen_pv_smp_prepare_cpus,
440 	.smp_cpus_done = xen_smp_cpus_done,
441 
442 	.cpu_up = xen_pv_cpu_up,
443 	.cpu_die = xen_pv_cpu_die,
444 	.cpu_disable = xen_pv_cpu_disable,
445 	.play_dead = xen_pv_play_dead,
446 
447 	.stop_other_cpus = xen_pv_stop_other_cpus,
448 	.smp_send_reschedule = xen_smp_send_reschedule,
449 
450 	.send_call_func_ipi = xen_smp_send_call_function_ipi,
451 	.send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
452 };
453 
454 void __init xen_smp_init(void)
455 {
456 	smp_ops = xen_smp_ops;
457 
458 	/* Avoid searching for BIOS MP tables */
459 	x86_init.mpparse.find_smp_config = x86_init_noop;
460 	x86_init.mpparse.get_smp_config = _get_smp_config;
461 }
462