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/apic.h>
33#include <asm/io_apic.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
53cpumask_var_t xen_cpu_initialized_map;
54
55static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
56static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
57
58static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
59
60static void cpu_bringup(void)
61{
62 int cpu;
63
64 cr4_init();
65 cpuhp_ap_sync_alive();
66 cpu_init();
67 fpu__init_cpu();
68 touch_softlockup_watchdog();
69
70 /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
71 if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
72 xen_enable_sysenter();
73 xen_enable_syscall();
74 }
75 cpu = smp_processor_id();
76 smp_store_cpu_info(id: cpu);
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, online: true);
86
87 smp_mb();
88
89 /* We can take interrupts now: we're officially "up". */
90 local_irq_enable();
91}
92
93asmlinkage __visible void cpu_bringup_and_idle(void)
94{
95 cpu_bringup();
96 cpu_startup_entry(state: CPUHP_AP_ONLINE_IDLE);
97}
98
99void 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
116int 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, fmt: "irqwork%d", cpu);
122 per_cpu(xen_irq_work, cpu).name = callfunc_name;
123 rc = bind_ipi_to_irqhandler(ipi: XEN_IRQ_WORK_VECTOR,
124 cpu,
125 handler: xen_irq_work_interrupt,
126 IRQF_PERCPU|IRQF_NOBALANCING,
127 devname: 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, fmt: "pmu%d", cpu);
135 per_cpu(xen_pmu_irq, cpu).name = pmu_name;
136 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
137 handler: xen_pmu_irq_handler,
138 IRQF_PERCPU|IRQF_NOBALANCING,
139 devname: 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
152static void __init xen_pv_smp_config(void)
153{
154 u32 apicid = 0;
155 int i;
156
157 topology_register_boot_apic(apic_id: apicid++);
158
159 for (i = 1; i < nr_cpu_ids; i++)
160 topology_register_apic(apic_id: apicid++, CPU_ACPIID_INVALID, present: true);
161
162 /* Pretend to be a proper enumerated system */
163 smp_found_config = 1;
164}
165
166static void __init xen_pv_smp_prepare_boot_cpu(void)
167{
168 BUG_ON(smp_processor_id() != 0);
169 native_smp_prepare_boot_cpu();
170
171 if (!xen_feature(XENFEAT_writable_page_tables))
172 /* We've switched to the "real" per-cpu gdt, so make
173 * sure the old memory can be recycled. */
174 make_lowmem_page_readwrite(vaddr: xen_initial_gdt);
175
176 xen_setup_vcpu_info_placement();
177
178 /*
179 * The alternative logic (which patches the unlock/lock) runs before
180 * the smp bootup up code is activated. Hence we need to set this up
181 * the core kernel is being patched. Otherwise we will have only
182 * modules patched but not core code.
183 */
184 xen_init_spinlocks();
185}
186
187static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
188{
189 unsigned cpu;
190
191 if (ioapic_is_disabled) {
192 char *m = (max_cpus == 0) ?
193 "The nosmp parameter is incompatible with Xen; " \
194 "use Xen dom0_max_vcpus=1 parameter" :
195 "The noapic parameter is incompatible with Xen";
196
197 xen_raw_printk(fmt: m);
198 panic(fmt: m);
199 }
200 xen_init_lock_cpu(cpu: 0);
201
202 smp_prepare_cpus_common();
203
204 speculative_store_bypass_ht_init();
205
206 xen_pmu_init(cpu: 0);
207
208 if (xen_smp_intr_init(cpu: 0) || xen_smp_intr_init_pv(cpu: 0))
209 BUG();
210
211 if (!alloc_cpumask_var(mask: &xen_cpu_initialized_map, GFP_KERNEL))
212 panic(fmt: "could not allocate xen_cpu_initialized_map\n");
213
214 cpumask_copy(dstp: xen_cpu_initialized_map, cpumask_of(0));
215
216 /* Restrict the possible_map according to max_cpus. */
217 while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
218 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
219 continue;
220 set_cpu_possible(cpu, possible: false);
221 }
222
223 for_each_possible_cpu(cpu)
224 set_cpu_present(cpu, present: true);
225}
226
227static int
228cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
229{
230 struct vcpu_guest_context *ctxt;
231 struct desc_struct *gdt;
232 unsigned long gdt_mfn;
233
234 if (cpumask_test_and_set_cpu(cpu, cpumask: xen_cpu_initialized_map))
235 return 0;
236
237 ctxt = kzalloc(size: sizeof(*ctxt), GFP_KERNEL);
238 if (ctxt == NULL) {
239 cpumask_clear_cpu(cpu, dstp: xen_cpu_initialized_map);
240 return -ENOMEM;
241 }
242
243 gdt = get_cpu_gdt_rw(cpu);
244
245 /*
246 * Bring up the CPU in cpu_bringup_and_idle() with the stack
247 * pointing just below where pt_regs would be if it were a normal
248 * kernel entry.
249 */
250 ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle;
251 ctxt->flags = VGCF_IN_KERNEL;
252 ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
253 ctxt->user_regs.ds = __USER_DS;
254 ctxt->user_regs.es = __USER_DS;
255 ctxt->user_regs.ss = __KERNEL_DS;
256 ctxt->user_regs.cs = __KERNEL_CS;
257 ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
258
259 xen_copy_trap_info(traps: ctxt->trap_ctxt);
260
261 BUG_ON((unsigned long)gdt & ~PAGE_MASK);
262
263 gdt_mfn = arbitrary_virt_to_mfn(vaddr: gdt);
264 make_lowmem_page_readonly(vaddr: gdt);
265 make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
266
267 ctxt->gdt_frames[0] = gdt_mfn;
268 ctxt->gdt_ents = GDT_ENTRIES;
269
270 /*
271 * Set SS:SP that Xen will use when entering guest kernel mode
272 * from guest user mode. Subsequent calls to load_sp0() can
273 * change this value.
274 */
275 ctxt->kernel_ss = __KERNEL_DS;
276 ctxt->kernel_sp = task_top_of_stack(idle);
277
278 ctxt->gs_base_kernel = per_cpu_offset(cpu);
279 ctxt->event_callback_eip =
280 (unsigned long)xen_asm_exc_xen_hypervisor_callback;
281 ctxt->failsafe_callback_eip =
282 (unsigned long)xen_failsafe_callback;
283 per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
284
285 ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
286 if (HYPERVISOR_vcpu_op(VCPUOP_initialise, vcpuid: xen_vcpu_nr(cpu), extra_args: ctxt))
287 BUG();
288
289 kfree(objp: ctxt);
290 return 0;
291}
292
293static int xen_pv_kick_ap(unsigned int cpu, struct task_struct *idle)
294{
295 int rc;
296
297 rc = common_cpu_up(cpunum: cpu, tidle: idle);
298 if (rc)
299 return rc;
300
301 xen_setup_runstate_info(cpu);
302
303 /* make sure interrupts start blocked */
304 per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
305
306 rc = cpu_initialize_context(cpu, idle);
307 if (rc)
308 return rc;
309
310 xen_pmu_init(cpu);
311
312 /*
313 * Why is this a BUG? If the hypercall fails then everything can be
314 * rolled back, no?
315 */
316 BUG_ON(HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL));
317
318 return 0;
319}
320
321static void xen_pv_poll_sync_state(void)
322{
323 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
324}
325
326#ifdef CONFIG_HOTPLUG_CPU
327static int xen_pv_cpu_disable(void)
328{
329 unsigned int cpu = smp_processor_id();
330 if (cpu == 0)
331 return -EBUSY;
332
333 cpu_disable_common();
334
335 load_cr3(swapper_pg_dir);
336 return 0;
337}
338
339static void xen_pv_cpu_die(unsigned int cpu)
340{
341 while (HYPERVISOR_vcpu_op(VCPUOP_is_up, vcpuid: xen_vcpu_nr(cpu), NULL)) {
342 __set_current_state(TASK_UNINTERRUPTIBLE);
343 schedule_timeout(HZ/10);
344 }
345}
346
347static void xen_pv_cleanup_dead_cpu(unsigned int cpu)
348{
349 xen_smp_intr_free(cpu);
350 xen_uninit_lock_cpu(cpu);
351 xen_teardown_timer(cpu);
352 xen_pmu_finish(cpu);
353}
354
355static void __noreturn xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
356{
357 play_dead_common();
358 HYPERVISOR_vcpu_op(VCPUOP_down, vcpuid: xen_vcpu_nr(smp_processor_id()), NULL);
359 xen_cpu_bringup_again(stack: (unsigned long)task_pt_regs(current));
360 BUG();
361}
362
363#else /* !CONFIG_HOTPLUG_CPU */
364static int xen_pv_cpu_disable(void)
365{
366 return -ENOSYS;
367}
368
369static void xen_pv_cpu_die(unsigned int cpu)
370{
371 BUG();
372}
373
374static void xen_pv_cleanup_dead_cpu(unsigned int cpu)
375{
376 BUG();
377}
378
379static void __noreturn xen_pv_play_dead(void)
380{
381 BUG();
382}
383
384#endif
385static void stop_self(void *v)
386{
387 int cpu = smp_processor_id();
388
389 /* make sure we're not pinning something down */
390 load_cr3(swapper_pg_dir);
391 /* should set up a minimal gdt */
392
393 set_cpu_online(cpu, online: false);
394
395 HYPERVISOR_vcpu_op(VCPUOP_down, vcpuid: xen_vcpu_nr(cpu), NULL);
396 BUG();
397}
398
399static void xen_pv_stop_other_cpus(int wait)
400{
401 smp_call_function(func: stop_self, NULL, wait);
402}
403
404static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
405{
406 irq_work_run();
407 inc_irq_stat(apic_irq_work_irqs);
408
409 return IRQ_HANDLED;
410}
411
412void __init xen_smp_count_cpus(void)
413{
414 unsigned int cpus;
415
416 for (cpus = 0; cpus < nr_cpu_ids; cpus++) {
417 if (HYPERVISOR_vcpu_op(VCPUOP_is_up, vcpuid: cpus, NULL) < 0)
418 break;
419 }
420
421 pr_info("Xen PV: Detected %u vCPUS\n", cpus);
422 if (cpus < nr_cpu_ids)
423 set_nr_cpu_ids(cpus);
424}
425
426static const struct smp_ops xen_smp_ops __initconst = {
427 .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
428 .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
429 .smp_cpus_done = xen_smp_cpus_done,
430
431 .kick_ap_alive = xen_pv_kick_ap,
432 .cpu_die = xen_pv_cpu_die,
433 .cleanup_dead_cpu = xen_pv_cleanup_dead_cpu,
434 .poll_sync_state = xen_pv_poll_sync_state,
435 .cpu_disable = xen_pv_cpu_disable,
436 .play_dead = xen_pv_play_dead,
437
438 .stop_other_cpus = xen_pv_stop_other_cpus,
439 .smp_send_reschedule = xen_smp_send_reschedule,
440
441 .send_call_func_ipi = xen_smp_send_call_function_ipi,
442 .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
443};
444
445void __init xen_smp_init(void)
446{
447 smp_ops = xen_smp_ops;
448
449 /* Avoid searching for BIOS MP tables */
450 x86_init.mpparse.find_mptable = x86_init_noop;
451 x86_init.mpparse.early_parse_smp_cfg = x86_init_noop;
452
453 /* XEN/PV Dom0 has halfways sane topology information via CPUID/MADT */
454 if (xen_initial_domain())
455 x86_init.mpparse.parse_smp_cfg = x86_init_noop;
456 else
457 x86_init.mpparse.parse_smp_cfg = xen_pv_smp_config;
458}
459

source code of linux/arch/x86/xen/smp_pv.c