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 #include <asm/fpu/internal.h>
34
35 #include <xen/interface/xen.h>
36 #include <xen/interface/vcpu.h>
37 #include <xen/interface/xenpmu.h>
38
39 #include <asm/spec-ctrl.h>
40 #include <asm/xen/interface.h>
41 #include <asm/xen/hypercall.h>
42
43 #include <xen/xen.h>
44 #include <xen/page.h>
45 #include <xen/events.h>
46
47 #include <xen/hvc-console.h>
48 #include "xen-ops.h"
49 #include "mmu.h"
50 #include "smp.h"
51 #include "pmu.h"
52
53 cpumask_var_t xen_cpu_initialized_map;
54
55 static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
56 static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
57
58 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
59 void asm_cpu_bringup_and_idle(void);
60
cpu_bringup(void)61 static void cpu_bringup(void)
62 {
63 int cpu;
64
65 cr4_init();
66 cpu_init();
67 fpu__init_cpu();
68 touch_softlockup_watchdog();
69 preempt_disable();
70
71 /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
72 if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
73 xen_enable_sysenter();
74 xen_enable_syscall();
75 }
76 cpu = smp_processor_id();
77 smp_store_cpu_info(cpu);
78 cpu_data(cpu).x86_max_cores = 1;
79 set_cpu_sibling_map(cpu);
80
81 speculative_store_bypass_ht_init();
82
83 xen_setup_cpu_clockevents();
84
85 notify_cpu_starting(cpu);
86
87 set_cpu_online(cpu, true);
88
89 cpu_set_state_online(cpu); /* Implies full memory barrier. */
90
91 /* We can take interrupts now: we're officially "up". */
92 local_irq_enable();
93 }
94
cpu_bringup_and_idle(void)95 asmlinkage __visible void cpu_bringup_and_idle(void)
96 {
97 cpu_bringup();
98 cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
99 }
100
xen_smp_intr_free_pv(unsigned int cpu)101 void xen_smp_intr_free_pv(unsigned int cpu)
102 {
103 kfree(per_cpu(xen_irq_work, cpu).name);
104 per_cpu(xen_irq_work, cpu).name = NULL;
105 if (per_cpu(xen_irq_work, cpu).irq >= 0) {
106 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
107 per_cpu(xen_irq_work, cpu).irq = -1;
108 }
109
110 kfree(per_cpu(xen_pmu_irq, cpu).name);
111 per_cpu(xen_pmu_irq, cpu).name = NULL;
112 if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
113 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
114 per_cpu(xen_pmu_irq, cpu).irq = -1;
115 }
116 }
117
xen_smp_intr_init_pv(unsigned int cpu)118 int xen_smp_intr_init_pv(unsigned int cpu)
119 {
120 int rc;
121 char *callfunc_name, *pmu_name;
122
123 callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
124 per_cpu(xen_irq_work, cpu).name = callfunc_name;
125 rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
126 cpu,
127 xen_irq_work_interrupt,
128 IRQF_PERCPU|IRQF_NOBALANCING,
129 callfunc_name,
130 NULL);
131 if (rc < 0)
132 goto fail;
133 per_cpu(xen_irq_work, cpu).irq = rc;
134
135 if (is_xen_pmu) {
136 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
137 per_cpu(xen_pmu_irq, cpu).name = pmu_name;
138 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
139 xen_pmu_irq_handler,
140 IRQF_PERCPU|IRQF_NOBALANCING,
141 pmu_name, NULL);
142 if (rc < 0)
143 goto fail;
144 per_cpu(xen_pmu_irq, cpu).irq = rc;
145 }
146
147 return 0;
148
149 fail:
150 xen_smp_intr_free_pv(cpu);
151 return rc;
152 }
153
_get_smp_config(unsigned int early)154 static void __init _get_smp_config(unsigned int early)
155 {
156 int i, rc;
157 unsigned int subtract = 0;
158
159 if (early)
160 return;
161
162 num_processors = 0;
163 disabled_cpus = 0;
164 for (i = 0; i < nr_cpu_ids; i++) {
165 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
166 if (rc >= 0) {
167 num_processors++;
168 set_cpu_possible(i, true);
169 } else {
170 set_cpu_possible(i, false);
171 set_cpu_present(i, false);
172 subtract++;
173 }
174 }
175 #ifdef CONFIG_HOTPLUG_CPU
176 /* This is akin to using 'nr_cpus' on the Linux command line.
177 * Which is OK as when we use 'dom0_max_vcpus=X' we can only
178 * have up to X, while nr_cpu_ids is greater than X. This
179 * normally is not a problem, except when CPU hotplugging
180 * is involved and then there might be more than X CPUs
181 * in the guest - which will not work as there is no
182 * hypercall to expand the max number of VCPUs an already
183 * running guest has. So cap it up to X. */
184 if (subtract)
185 nr_cpu_ids = nr_cpu_ids - subtract;
186 #endif
187
188 }
189
xen_pv_smp_prepare_boot_cpu(void)190 static void __init xen_pv_smp_prepare_boot_cpu(void)
191 {
192 BUG_ON(smp_processor_id() != 0);
193 native_smp_prepare_boot_cpu();
194
195 if (!xen_feature(XENFEAT_writable_page_tables))
196 /* We've switched to the "real" per-cpu gdt, so make
197 * sure the old memory can be recycled. */
198 make_lowmem_page_readwrite(xen_initial_gdt);
199
200 xen_setup_vcpu_info_placement();
201
202 /*
203 * The alternative logic (which patches the unlock/lock) runs before
204 * the smp bootup up code is activated. Hence we need to set this up
205 * the core kernel is being patched. Otherwise we will have only
206 * modules patched but not core code.
207 */
208 xen_init_spinlocks();
209 }
210
xen_pv_smp_prepare_cpus(unsigned int max_cpus)211 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
212 {
213 unsigned cpu;
214 unsigned int i;
215
216 if (skip_ioapic_setup) {
217 char *m = (max_cpus == 0) ?
218 "The nosmp parameter is incompatible with Xen; " \
219 "use Xen dom0_max_vcpus=1 parameter" :
220 "The noapic parameter is incompatible with Xen";
221
222 xen_raw_printk(m);
223 panic(m);
224 }
225 xen_init_lock_cpu(0);
226
227 smp_store_boot_cpu_info();
228 cpu_data(0).x86_max_cores = 1;
229
230 for_each_possible_cpu(i) {
231 zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
232 zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
233 zalloc_cpumask_var(&per_cpu(cpu_die_map, i), GFP_KERNEL);
234 zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
235 }
236 set_cpu_sibling_map(0);
237
238 speculative_store_bypass_ht_init();
239
240 xen_pmu_init(0);
241
242 if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
243 BUG();
244
245 if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
246 panic("could not allocate xen_cpu_initialized_map\n");
247
248 cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
249
250 /* Restrict the possible_map according to max_cpus. */
251 while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
252 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
253 continue;
254 set_cpu_possible(cpu, false);
255 }
256
257 for_each_possible_cpu(cpu)
258 set_cpu_present(cpu, true);
259 }
260
261 static int
cpu_initialize_context(unsigned int cpu,struct task_struct * idle)262 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
263 {
264 struct vcpu_guest_context *ctxt;
265 struct desc_struct *gdt;
266 unsigned long gdt_mfn;
267
268 /* used to tell cpu_init() that it can proceed with initialization */
269 cpumask_set_cpu(cpu, cpu_callout_mask);
270 if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
271 return 0;
272
273 ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
274 if (ctxt == NULL)
275 return -ENOMEM;
276
277 gdt = get_cpu_gdt_rw(cpu);
278
279 memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
280
281 /*
282 * Bring up the CPU in cpu_bringup_and_idle() with the stack
283 * pointing just below where pt_regs would be if it were a normal
284 * kernel entry.
285 */
286 ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle;
287 ctxt->flags = VGCF_IN_KERNEL;
288 ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
289 ctxt->user_regs.ds = __USER_DS;
290 ctxt->user_regs.es = __USER_DS;
291 ctxt->user_regs.ss = __KERNEL_DS;
292 ctxt->user_regs.cs = __KERNEL_CS;
293 ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
294
295 xen_copy_trap_info(ctxt->trap_ctxt);
296
297 ctxt->ldt_ents = 0;
298
299 BUG_ON((unsigned long)gdt & ~PAGE_MASK);
300
301 gdt_mfn = arbitrary_virt_to_mfn(gdt);
302 make_lowmem_page_readonly(gdt);
303 make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
304
305 ctxt->gdt_frames[0] = gdt_mfn;
306 ctxt->gdt_ents = GDT_ENTRIES;
307
308 /*
309 * Set SS:SP that Xen will use when entering guest kernel mode
310 * from guest user mode. Subsequent calls to load_sp0() can
311 * change this value.
312 */
313 ctxt->kernel_ss = __KERNEL_DS;
314 ctxt->kernel_sp = task_top_of_stack(idle);
315
316 ctxt->gs_base_kernel = per_cpu_offset(cpu);
317 ctxt->event_callback_eip =
318 (unsigned long)xen_asm_exc_xen_hypervisor_callback;
319 ctxt->failsafe_callback_eip =
320 (unsigned long)xen_failsafe_callback;
321 per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
322
323 ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
324 if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
325 BUG();
326
327 kfree(ctxt);
328 return 0;
329 }
330
xen_pv_cpu_up(unsigned int cpu,struct task_struct * idle)331 static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
332 {
333 int rc;
334
335 rc = common_cpu_up(cpu, idle);
336 if (rc)
337 return rc;
338
339 xen_setup_runstate_info(cpu);
340
341 /*
342 * PV VCPUs are always successfully taken down (see 'while' loop
343 * in xen_cpu_die()), so -EBUSY is an error.
344 */
345 rc = cpu_check_up_prepare(cpu);
346 if (rc)
347 return rc;
348
349 /* make sure interrupts start blocked */
350 per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
351
352 rc = cpu_initialize_context(cpu, idle);
353 if (rc)
354 return rc;
355
356 xen_pmu_init(cpu);
357
358 rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
359 BUG_ON(rc);
360
361 while (cpu_report_state(cpu) != CPU_ONLINE)
362 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
363
364 return 0;
365 }
366
367 #ifdef CONFIG_HOTPLUG_CPU
xen_pv_cpu_disable(void)368 static int xen_pv_cpu_disable(void)
369 {
370 unsigned int cpu = smp_processor_id();
371 if (cpu == 0)
372 return -EBUSY;
373
374 cpu_disable_common();
375
376 load_cr3(swapper_pg_dir);
377 return 0;
378 }
379
xen_pv_cpu_die(unsigned int cpu)380 static void xen_pv_cpu_die(unsigned int cpu)
381 {
382 while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
383 xen_vcpu_nr(cpu), NULL)) {
384 __set_current_state(TASK_UNINTERRUPTIBLE);
385 schedule_timeout(HZ/10);
386 }
387
388 if (common_cpu_die(cpu) == 0) {
389 xen_smp_intr_free(cpu);
390 xen_uninit_lock_cpu(cpu);
391 xen_teardown_timer(cpu);
392 xen_pmu_finish(cpu);
393 }
394 }
395
xen_pv_play_dead(void)396 static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
397 {
398 play_dead_common();
399 HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
400 cpu_bringup();
401 /*
402 * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
403 * clears certain data that the cpu_idle loop (which called us
404 * and that we return from) expects. The only way to get that
405 * data back is to call:
406 */
407 tick_nohz_idle_enter();
408 tick_nohz_idle_stop_tick_protected();
409
410 cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE);
411 }
412
413 #else /* !CONFIG_HOTPLUG_CPU */
xen_pv_cpu_disable(void)414 static int xen_pv_cpu_disable(void)
415 {
416 return -ENOSYS;
417 }
418
xen_pv_cpu_die(unsigned int cpu)419 static void xen_pv_cpu_die(unsigned int cpu)
420 {
421 BUG();
422 }
423
xen_pv_play_dead(void)424 static void xen_pv_play_dead(void)
425 {
426 BUG();
427 }
428
429 #endif
stop_self(void * v)430 static void stop_self(void *v)
431 {
432 int cpu = smp_processor_id();
433
434 /* make sure we're not pinning something down */
435 load_cr3(swapper_pg_dir);
436 /* should set up a minimal gdt */
437
438 set_cpu_online(cpu, false);
439
440 HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
441 BUG();
442 }
443
xen_pv_stop_other_cpus(int wait)444 static void xen_pv_stop_other_cpus(int wait)
445 {
446 smp_call_function(stop_self, NULL, wait);
447 }
448
xen_irq_work_interrupt(int irq,void * dev_id)449 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
450 {
451 irq_enter();
452 irq_work_run();
453 inc_irq_stat(apic_irq_work_irqs);
454 irq_exit();
455
456 return IRQ_HANDLED;
457 }
458
459 static const struct smp_ops xen_smp_ops __initconst = {
460 .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
461 .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
462 .smp_cpus_done = xen_smp_cpus_done,
463
464 .cpu_up = xen_pv_cpu_up,
465 .cpu_die = xen_pv_cpu_die,
466 .cpu_disable = xen_pv_cpu_disable,
467 .play_dead = xen_pv_play_dead,
468
469 .stop_other_cpus = xen_pv_stop_other_cpus,
470 .smp_send_reschedule = xen_smp_send_reschedule,
471
472 .send_call_func_ipi = xen_smp_send_call_function_ipi,
473 .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
474 };
475
xen_smp_init(void)476 void __init xen_smp_init(void)
477 {
478 smp_ops = xen_smp_ops;
479
480 /* Avoid searching for BIOS MP tables */
481 x86_init.mpparse.find_smp_config = x86_init_noop;
482 x86_init.mpparse.get_smp_config = _get_smp_config;
483 }
484