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
cpu_bringup(void)60 static void cpu_bringup(void)
61 {
62 int cpu;
63
64 cr4_init();
65 cpu_init();
66 touch_softlockup_watchdog();
67 preempt_disable();
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
cpu_bringup_and_idle(void)93 asmlinkage __visible void cpu_bringup_and_idle(void)
94 {
95 cpu_bringup();
96 cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
97 }
98
xen_smp_intr_free_pv(unsigned int cpu)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
xen_smp_intr_init_pv(unsigned int cpu)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
_get_smp_config(unsigned int early)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 nr_cpu_ids = nr_cpu_ids - subtract;
184 #endif
185
186 }
187
xen_pv_smp_prepare_boot_cpu(void)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
xen_pv_smp_prepare_cpus(unsigned int max_cpus)209 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
210 {
211 unsigned cpu;
212 unsigned int i;
213
214 if (skip_ioapic_setup) {
215 char *m = (max_cpus == 0) ?
216 "The nosmp parameter is incompatible with Xen; " \
217 "use Xen dom0_max_vcpus=1 parameter" :
218 "The noapic parameter is incompatible with Xen";
219
220 xen_raw_printk(m);
221 panic(m);
222 }
223 xen_init_lock_cpu(0);
224
225 smp_store_boot_cpu_info();
226 cpu_data(0).x86_max_cores = 1;
227
228 for_each_possible_cpu(i) {
229 zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
230 zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
231 zalloc_cpumask_var(&per_cpu(cpu_die_map, i), GFP_KERNEL);
232 zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
233 }
234 set_cpu_sibling_map(0);
235
236 speculative_store_bypass_ht_init();
237
238 xen_pmu_init(0);
239
240 if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
241 BUG();
242
243 if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
244 panic("could not allocate xen_cpu_initialized_map\n");
245
246 cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
247
248 /* Restrict the possible_map according to max_cpus. */
249 while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
250 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
251 continue;
252 set_cpu_possible(cpu, false);
253 }
254
255 for_each_possible_cpu(cpu)
256 set_cpu_present(cpu, true);
257 }
258
259 static int
cpu_initialize_context(unsigned int cpu,struct task_struct * idle)260 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
261 {
262 struct vcpu_guest_context *ctxt;
263 struct desc_struct *gdt;
264 unsigned long gdt_mfn;
265
266 /* used to tell cpu_init() that it can proceed with initialization */
267 cpumask_set_cpu(cpu, cpu_callout_mask);
268 if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
269 return 0;
270
271 ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
272 if (ctxt == NULL)
273 return -ENOMEM;
274
275 gdt = get_cpu_gdt_rw(cpu);
276
277 memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
278
279 /*
280 * Bring up the CPU in cpu_bringup_and_idle() with the stack
281 * pointing just below where pt_regs would be if it were a normal
282 * kernel entry.
283 */
284 ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle;
285 ctxt->flags = VGCF_IN_KERNEL;
286 ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
287 ctxt->user_regs.ds = __USER_DS;
288 ctxt->user_regs.es = __USER_DS;
289 ctxt->user_regs.ss = __KERNEL_DS;
290 ctxt->user_regs.cs = __KERNEL_CS;
291 ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
292
293 xen_copy_trap_info(ctxt->trap_ctxt);
294
295 ctxt->ldt_ents = 0;
296
297 BUG_ON((unsigned long)gdt & ~PAGE_MASK);
298
299 gdt_mfn = arbitrary_virt_to_mfn(gdt);
300 make_lowmem_page_readonly(gdt);
301 make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
302
303 ctxt->gdt_frames[0] = gdt_mfn;
304 ctxt->gdt_ents = GDT_ENTRIES;
305
306 /*
307 * Set SS:SP that Xen will use when entering guest kernel mode
308 * from guest user mode. Subsequent calls to load_sp0() can
309 * change this value.
310 */
311 ctxt->kernel_ss = __KERNEL_DS;
312 ctxt->kernel_sp = task_top_of_stack(idle);
313
314 ctxt->gs_base_kernel = per_cpu_offset(cpu);
315 ctxt->event_callback_eip =
316 (unsigned long)xen_asm_exc_xen_hypervisor_callback;
317 ctxt->failsafe_callback_eip =
318 (unsigned long)xen_failsafe_callback;
319 per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
320
321 ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
322 if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
323 BUG();
324
325 kfree(ctxt);
326 return 0;
327 }
328
xen_pv_cpu_up(unsigned int cpu,struct task_struct * idle)329 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
330 {
331 int rc;
332
333 rc = common_cpu_up(cpu, idle);
334 if (rc)
335 return rc;
336
337 xen_setup_runstate_info(cpu);
338
339 /*
340 * PV VCPUs are always successfully taken down (see 'while' loop
341 * in xen_cpu_die()), so -EBUSY is an error.
342 */
343 rc = cpu_check_up_prepare(cpu);
344 if (rc)
345 return rc;
346
347 /* make sure interrupts start blocked */
348 per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
349
350 rc = cpu_initialize_context(cpu, idle);
351 if (rc)
352 return rc;
353
354 xen_pmu_init(cpu);
355
356 rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
357 BUG_ON(rc);
358
359 while (cpu_report_state(cpu) != CPU_ONLINE)
360 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
361
362 return 0;
363 }
364
365 #ifdef CONFIG_HOTPLUG_CPU
xen_pv_cpu_disable(void)366 static int xen_pv_cpu_disable(void)
367 {
368 unsigned int cpu = smp_processor_id();
369 if (cpu == 0)
370 return -EBUSY;
371
372 cpu_disable_common();
373
374 load_cr3(swapper_pg_dir);
375 return 0;
376 }
377
xen_pv_cpu_die(unsigned int cpu)378 static void xen_pv_cpu_die(unsigned int cpu)
379 {
380 while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
381 xen_vcpu_nr(cpu), NULL)) {
382 __set_current_state(TASK_UNINTERRUPTIBLE);
383 schedule_timeout(HZ/10);
384 }
385
386 if (common_cpu_die(cpu) == 0) {
387 xen_smp_intr_free(cpu);
388 xen_uninit_lock_cpu(cpu);
389 xen_teardown_timer(cpu);
390 xen_pmu_finish(cpu);
391 }
392 }
393
xen_pv_play_dead(void)394 static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
395 {
396 play_dead_common();
397 HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
398 cpu_bringup();
399 /*
400 * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
401 * clears certain data that the cpu_idle loop (which called us
402 * and that we return from) expects. The only way to get that
403 * data back is to call:
404 */
405 tick_nohz_idle_enter();
406 tick_nohz_idle_stop_tick_protected();
407
408 cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE);
409 }
410
411 #else /* !CONFIG_HOTPLUG_CPU */
xen_pv_cpu_disable(void)412 static int xen_pv_cpu_disable(void)
413 {
414 return -ENOSYS;
415 }
416
xen_pv_cpu_die(unsigned int cpu)417 static void xen_pv_cpu_die(unsigned int cpu)
418 {
419 BUG();
420 }
421
xen_pv_play_dead(void)422 static void xen_pv_play_dead(void)
423 {
424 BUG();
425 }
426
427 #endif
stop_self(void * v)428 static void stop_self(void *v)
429 {
430 int cpu = smp_processor_id();
431
432 /* make sure we're not pinning something down */
433 load_cr3(swapper_pg_dir);
434 /* should set up a minimal gdt */
435
436 set_cpu_online(cpu, false);
437
438 HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
439 BUG();
440 }
441
xen_pv_stop_other_cpus(int wait)442 static void xen_pv_stop_other_cpus(int wait)
443 {
444 smp_call_function(stop_self, NULL, wait);
445 }
446
xen_irq_work_interrupt(int irq,void * dev_id)447 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
448 {
449 irq_enter();
450 irq_work_run();
451 inc_irq_stat(apic_irq_work_irqs);
452 irq_exit();
453
454 return IRQ_HANDLED;
455 }
456
457 static const struct smp_ops xen_smp_ops __initconst = {
458 .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
459 .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
460 .smp_cpus_done = xen_smp_cpus_done,
461
462 .cpu_up = xen_pv_cpu_up,
463 .cpu_die = xen_pv_cpu_die,
464 .cpu_disable = xen_pv_cpu_disable,
465 .play_dead = xen_pv_play_dead,
466
467 .stop_other_cpus = xen_pv_stop_other_cpus,
468 .smp_send_reschedule = xen_smp_send_reschedule,
469
470 .send_call_func_ipi = xen_smp_send_call_function_ipi,
471 .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
472 };
473
xen_smp_init(void)474 void __init xen_smp_init(void)
475 {
476 smp_ops = xen_smp_ops;
477
478 /* Avoid searching for BIOS MP tables */
479 x86_init.mpparse.find_smp_config = x86_init_noop;
480 x86_init.mpparse.get_smp_config = _get_smp_config;
481 }
482