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(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, 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(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, "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
152static void __init xen_pv_smp_config(void)
153{
154	u32 apicid = 0;
155	int i;
156
157	topology_register_boot_apic(apicid++);
158
159	for (i = 1; i < nr_cpu_ids; i++)
160		topology_register_apic(apicid++, CPU_ACPIID_INVALID, 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(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(m);
198		panic(m);
199	}
200	xen_init_lock_cpu(0);
201
202	smp_prepare_cpus_common();
203
204	speculative_store_bypass_ht_init();
205
206	xen_pmu_init(0);
207
208	if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
209		BUG();
210
211	if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
212		panic("could not allocate xen_cpu_initialized_map\n");
213
214	cpumask_copy(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, false);
221	}
222
223	for_each_possible_cpu(cpu)
224		set_cpu_present(cpu, 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, xen_cpu_initialized_map))
235		return 0;
236
237	ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
238	if (ctxt == NULL) {
239		cpumask_clear_cpu(cpu, 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(ctxt->trap_ctxt);
260
261	BUG_ON((unsigned long)gdt & ~PAGE_MASK);
262
263	gdt_mfn = arbitrary_virt_to_mfn(gdt);
264	make_lowmem_page_readonly(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, xen_vcpu_nr(cpu), ctxt))
287		BUG();
288
289	kfree(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(cpu, 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, 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, xen_vcpu_nr(smp_processor_id()), NULL);
359	xen_cpu_bringup_again((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, false);
394
395	HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
396	BUG();
397}
398
399static void xen_pv_stop_other_cpus(int wait)
400{
401	smp_call_function(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, 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