1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * HyperV Detection code.
4 *
5 * Copyright (C) 2010, Novell, Inc.
6 * Author : K. Y. Srinivasan <ksrinivasan@novell.com>
7 */
8
9#include <linux/types.h>
10#include <linux/time.h>
11#include <linux/clocksource.h>
12#include <linux/init.h>
13#include <linux/export.h>
14#include <linux/hardirq.h>
15#include <linux/efi.h>
16#include <linux/interrupt.h>
17#include <linux/irq.h>
18#include <linux/kexec.h>
19#include <linux/random.h>
20#include <asm/processor.h>
21#include <asm/hypervisor.h>
22#include <hyperv/hvhdk.h>
23#include <asm/mshyperv.h>
24#include <asm/desc.h>
25#include <asm/idtentry.h>
26#include <asm/irq_regs.h>
27#include <asm/i8259.h>
28#include <asm/apic.h>
29#include <asm/timer.h>
30#include <asm/reboot.h>
31#include <asm/msr.h>
32#include <asm/nmi.h>
33#include <clocksource/hyperv_timer.h>
34#include <asm/numa.h>
35#include <asm/svm.h>
36
37/* Is Linux running on nested Microsoft Hypervisor */
38bool hv_nested;
39struct ms_hyperv_info ms_hyperv;
40
41#if IS_ENABLED(CONFIG_HYPERV)
42/*
43 * When running with the paravisor, controls proxying the synthetic interrupts
44 * from the host
45 */
46static bool hv_para_sint_proxy;
47
48static inline unsigned int hv_get_nested_msr(unsigned int reg)
49{
50 if (hv_is_sint_msr(reg))
51 return reg - HV_X64_MSR_SINT0 + HV_X64_MSR_NESTED_SINT0;
52
53 switch (reg) {
54 case HV_X64_MSR_SIMP:
55 return HV_X64_MSR_NESTED_SIMP;
56 case HV_X64_MSR_SIEFP:
57 return HV_X64_MSR_NESTED_SIEFP;
58 case HV_X64_MSR_SVERSION:
59 return HV_X64_MSR_NESTED_SVERSION;
60 case HV_X64_MSR_SCONTROL:
61 return HV_X64_MSR_NESTED_SCONTROL;
62 case HV_X64_MSR_EOM:
63 return HV_X64_MSR_NESTED_EOM;
64 default:
65 return reg;
66 }
67}
68
69u64 hv_get_non_nested_msr(unsigned int reg)
70{
71 u64 value;
72
73 if (hv_is_synic_msr(reg) && ms_hyperv.paravisor_present)
74 hv_ivm_msr_read(msr: reg, value: &value);
75 else
76 rdmsrq(reg, value);
77 return value;
78}
79EXPORT_SYMBOL_GPL(hv_get_non_nested_msr);
80
81void hv_set_non_nested_msr(unsigned int reg, u64 value)
82{
83 if (hv_is_synic_msr(reg) && ms_hyperv.paravisor_present) {
84 /* The hypervisor will get the intercept. */
85 hv_ivm_msr_write(msr: reg, value);
86
87 /* Using wrmsrq so the following goes to the paravisor. */
88 if (hv_is_sint_msr(reg)) {
89 union hv_synic_sint sint = { .as_uint64 = value };
90
91 sint.proxy = hv_para_sint_proxy;
92 native_wrmsrq(reg, sint.as_uint64);
93 }
94 } else {
95 native_wrmsrq(reg, value);
96 }
97}
98EXPORT_SYMBOL_GPL(hv_set_non_nested_msr);
99
100/*
101 * Enable or disable proxying synthetic interrupts
102 * to the paravisor.
103 */
104void hv_para_set_sint_proxy(bool enable)
105{
106 hv_para_sint_proxy = enable;
107}
108
109/*
110 * Get the SynIC register value from the paravisor.
111 */
112u64 hv_para_get_synic_register(unsigned int reg)
113{
114 if (WARN_ON(!ms_hyperv.paravisor_present || !hv_is_synic_msr(reg)))
115 return ~0ULL;
116 return native_read_msr(msr: reg);
117}
118
119/*
120 * Set the SynIC register value with the paravisor.
121 */
122void hv_para_set_synic_register(unsigned int reg, u64 val)
123{
124 if (WARN_ON(!ms_hyperv.paravisor_present || !hv_is_synic_msr(reg)))
125 return;
126 native_write_msr(msr: reg, val);
127}
128
129u64 hv_get_msr(unsigned int reg)
130{
131 if (hv_nested)
132 reg = hv_get_nested_msr(reg);
133
134 return hv_get_non_nested_msr(reg);
135}
136EXPORT_SYMBOL_GPL(hv_get_msr);
137
138void hv_set_msr(unsigned int reg, u64 value)
139{
140 if (hv_nested)
141 reg = hv_get_nested_msr(reg);
142
143 hv_set_non_nested_msr(reg, value);
144}
145EXPORT_SYMBOL_GPL(hv_set_msr);
146
147static void (*mshv_handler)(void);
148static void (*vmbus_handler)(void);
149static void (*hv_stimer0_handler)(void);
150static void (*hv_kexec_handler)(void);
151static void (*hv_crash_handler)(struct pt_regs *regs);
152
153DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_callback)
154{
155 struct pt_regs *old_regs = set_irq_regs(regs);
156
157 inc_irq_stat(irq_hv_callback_count);
158 if (mshv_handler)
159 mshv_handler();
160
161 if (vmbus_handler)
162 vmbus_handler();
163
164 if (ms_hyperv.hints & HV_DEPRECATING_AEOI_RECOMMENDED)
165 apic_eoi();
166
167 set_irq_regs(old_regs);
168}
169
170void hv_setup_mshv_handler(void (*handler)(void))
171{
172 mshv_handler = handler;
173}
174
175void hv_setup_vmbus_handler(void (*handler)(void))
176{
177 vmbus_handler = handler;
178}
179
180void hv_remove_vmbus_handler(void)
181{
182 /* We have no way to deallocate the interrupt gate */
183 vmbus_handler = NULL;
184}
185
186/*
187 * Routines to do per-architecture handling of stimer0
188 * interrupts when in Direct Mode
189 */
190DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_stimer0)
191{
192 struct pt_regs *old_regs = set_irq_regs(regs);
193
194 inc_irq_stat(hyperv_stimer0_count);
195 if (hv_stimer0_handler)
196 hv_stimer0_handler();
197 add_interrupt_randomness(HYPERV_STIMER0_VECTOR);
198 apic_eoi();
199
200 set_irq_regs(old_regs);
201}
202
203/* For x86/x64, override weak placeholders in hyperv_timer.c */
204void hv_setup_stimer0_handler(void (*handler)(void))
205{
206 hv_stimer0_handler = handler;
207}
208
209void hv_remove_stimer0_handler(void)
210{
211 /* We have no way to deallocate the interrupt gate */
212 hv_stimer0_handler = NULL;
213}
214
215void hv_setup_kexec_handler(void (*handler)(void))
216{
217 hv_kexec_handler = handler;
218}
219
220void hv_remove_kexec_handler(void)
221{
222 hv_kexec_handler = NULL;
223}
224
225void hv_setup_crash_handler(void (*handler)(struct pt_regs *regs))
226{
227 hv_crash_handler = handler;
228}
229
230void hv_remove_crash_handler(void)
231{
232 hv_crash_handler = NULL;
233}
234
235#ifdef CONFIG_KEXEC_CORE
236static void hv_machine_shutdown(void)
237{
238 if (kexec_in_progress && hv_kexec_handler)
239 hv_kexec_handler();
240
241 /*
242 * Call hv_cpu_die() on all the CPUs, otherwise later the hypervisor
243 * corrupts the old VP Assist Pages and can crash the kexec kernel.
244 */
245 if (kexec_in_progress)
246 cpuhp_remove_state(state: CPUHP_AP_HYPERV_ONLINE);
247
248 /* The function calls stop_other_cpus(). */
249 native_machine_shutdown();
250
251 /* Disable the hypercall page when there is only 1 active CPU. */
252 if (kexec_in_progress)
253 hyperv_cleanup();
254}
255#endif /* CONFIG_KEXEC_CORE */
256
257#ifdef CONFIG_CRASH_DUMP
258static void hv_guest_crash_shutdown(struct pt_regs *regs)
259{
260 if (hv_crash_handler)
261 hv_crash_handler(regs);
262
263 /* The function calls crash_smp_send_stop(). */
264 native_machine_crash_shutdown(regs);
265
266 /* Disable the hypercall page when there is only 1 active CPU. */
267 hyperv_cleanup();
268}
269#endif /* CONFIG_CRASH_DUMP */
270
271static u64 hv_ref_counter_at_suspend;
272static void (*old_save_sched_clock_state)(void);
273static void (*old_restore_sched_clock_state)(void);
274
275/*
276 * Hyper-V clock counter resets during hibernation. Save and restore clock
277 * offset during suspend/resume, while also considering the time passed
278 * before suspend. This is to make sure that sched_clock using hv tsc page
279 * based clocksource, proceeds from where it left off during suspend and
280 * it shows correct time for the timestamps of kernel messages after resume.
281 */
282static void save_hv_clock_tsc_state(void)
283{
284 hv_ref_counter_at_suspend = hv_read_reference_counter();
285}
286
287static void restore_hv_clock_tsc_state(void)
288{
289 /*
290 * Adjust the offsets used by hv tsc clocksource to
291 * account for the time spent before hibernation.
292 * adjusted value = reference counter (time) at suspend
293 * - reference counter (time) now.
294 */
295 hv_adj_sched_clock_offset(offset: hv_ref_counter_at_suspend - hv_read_reference_counter());
296}
297
298/*
299 * Functions to override save_sched_clock_state and restore_sched_clock_state
300 * functions of x86_platform. The Hyper-V clock counter is reset during
301 * suspend-resume and the offset used to measure time needs to be
302 * corrected, post resume.
303 */
304static void hv_save_sched_clock_state(void)
305{
306 old_save_sched_clock_state();
307 save_hv_clock_tsc_state();
308}
309
310static void hv_restore_sched_clock_state(void)
311{
312 restore_hv_clock_tsc_state();
313 old_restore_sched_clock_state();
314}
315
316static void __init x86_setup_ops_for_tsc_pg_clock(void)
317{
318 if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
319 return;
320
321 old_save_sched_clock_state = x86_platform.save_sched_clock_state;
322 x86_platform.save_sched_clock_state = hv_save_sched_clock_state;
323
324 old_restore_sched_clock_state = x86_platform.restore_sched_clock_state;
325 x86_platform.restore_sched_clock_state = hv_restore_sched_clock_state;
326}
327
328#ifdef CONFIG_X86_64
329DEFINE_STATIC_CALL(hv_hypercall, hv_std_hypercall);
330EXPORT_STATIC_CALL_TRAMP_GPL(hv_hypercall);
331#define hypercall_update(hc) static_call_update(hv_hypercall, hc)
332#endif
333#endif /* CONFIG_HYPERV */
334
335#ifndef hypercall_update
336#define hypercall_update(hc) (void)hc
337#endif
338
339static uint32_t __init ms_hyperv_platform(void)
340{
341 u32 eax;
342 u32 hyp_signature[3];
343
344 if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
345 return 0;
346
347 cpuid(HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS,
348 eax: &eax, ebx: &hyp_signature[0], ecx: &hyp_signature[1], edx: &hyp_signature[2]);
349
350 if (eax < HYPERV_CPUID_MIN || eax > HYPERV_CPUID_MAX ||
351 memcmp(p: "Microsoft Hv", q: hyp_signature, size: 12))
352 return 0;
353
354 /* HYPERCALL and VP_INDEX MSRs are mandatory for all features. */
355 eax = cpuid_eax(HYPERV_CPUID_FEATURES);
356 if (!(eax & HV_MSR_HYPERCALL_AVAILABLE)) {
357 pr_warn("x86/hyperv: HYPERCALL MSR not available.\n");
358 return 0;
359 }
360 if (!(eax & HV_MSR_VP_INDEX_AVAILABLE)) {
361 pr_warn("x86/hyperv: VP_INDEX MSR not available.\n");
362 return 0;
363 }
364
365 return HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS;
366}
367
368#ifdef CONFIG_X86_LOCAL_APIC
369/*
370 * Prior to WS2016 Debug-VM sends NMIs to all CPUs which makes
371 * it difficult to process CHANNELMSG_UNLOAD in case of crash. Handle
372 * unknown NMI on the first CPU which gets it.
373 */
374static int hv_nmi_unknown(unsigned int val, struct pt_regs *regs)
375{
376 static atomic_t nmi_cpu = ATOMIC_INIT(-1);
377 unsigned int old_cpu, this_cpu;
378
379 if (!unknown_nmi_panic)
380 return NMI_DONE;
381
382 old_cpu = -1;
383 this_cpu = raw_smp_processor_id();
384 if (!atomic_try_cmpxchg(v: &nmi_cpu, old: &old_cpu, new: this_cpu))
385 return NMI_HANDLED;
386
387 return NMI_DONE;
388}
389#endif
390
391static unsigned long hv_get_tsc_khz(void)
392{
393 unsigned long freq;
394
395 rdmsrq(HV_X64_MSR_TSC_FREQUENCY, freq);
396
397 return freq / 1000;
398}
399
400#if defined(CONFIG_SMP) && IS_ENABLED(CONFIG_HYPERV)
401static void __init hv_smp_prepare_boot_cpu(void)
402{
403 native_smp_prepare_boot_cpu();
404#if defined(CONFIG_X86_64) && defined(CONFIG_PARAVIRT_SPINLOCKS)
405 hv_init_spinlocks();
406#endif
407}
408
409static void __init hv_smp_prepare_cpus(unsigned int max_cpus)
410{
411#ifdef CONFIG_X86_64
412 int i;
413 int ret;
414#endif
415
416 native_smp_prepare_cpus(max_cpus);
417
418 /*
419 * Override wakeup_secondary_cpu_64 callback for SEV-SNP
420 * enlightened guest.
421 */
422 if (!ms_hyperv.paravisor_present && hv_isolation_type_snp()) {
423 apic->wakeup_secondary_cpu_64 = hv_snp_boot_ap;
424 return;
425 }
426
427#ifdef CONFIG_X86_64
428 for_each_present_cpu(i) {
429 if (i == 0)
430 continue;
431 ret = hv_call_add_logical_proc(node: numa_cpu_node(cpu: i), lp_index: i, cpu_physical_id(i));
432 BUG_ON(ret);
433 }
434
435 for_each_present_cpu(i) {
436 if (i == 0)
437 continue;
438 ret = hv_call_create_vp(node: numa_cpu_node(cpu: i), partition_id: hv_current_partition_id, vp_index: i, flags: i);
439 BUG_ON(ret);
440 }
441#endif
442}
443#endif
444
445/*
446 * When a fully enlightened TDX VM runs on Hyper-V, the firmware sets the
447 * HW_REDUCED flag: refer to acpi_tb_create_local_fadt(). Consequently ttyS0
448 * interrupts can't work because request_irq() -> ... -> irq_to_desc() returns
449 * NULL for ttyS0. This happens because mp_config_acpi_legacy_irqs() sees a
450 * nr_legacy_irqs() of 0, so it doesn't initialize the array 'mp_irqs[]', and
451 * later setup_IO_APIC_irqs() -> find_irq_entry() fails to find the legacy irqs
452 * from the array and hence doesn't create the necessary irq description info.
453 *
454 * Clone arch/x86/kernel/acpi/boot.c: acpi_generic_reduced_hw_init() here,
455 * except don't change 'legacy_pic', which keeps its default value
456 * 'default_legacy_pic'. This way, mp_config_acpi_legacy_irqs() sees a non-zero
457 * nr_legacy_irqs() and eventually serial console interrupts works properly.
458 */
459static void __init reduced_hw_init(void)
460{
461 x86_init.timers.timer_init = x86_init_noop;
462 x86_init.irqs.pre_vector_init = x86_init_noop;
463}
464
465int hv_get_hypervisor_version(union hv_hypervisor_version_info *info)
466{
467 unsigned int hv_max_functions;
468
469 hv_max_functions = cpuid_eax(HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS);
470 if (hv_max_functions < HYPERV_CPUID_VERSION) {
471 pr_err("%s: Could not detect Hyper-V version\n", __func__);
472 return -ENODEV;
473 }
474
475 cpuid(HYPERV_CPUID_VERSION, eax: &info->eax, ebx: &info->ebx, ecx: &info->ecx, edx: &info->edx);
476
477 return 0;
478}
479EXPORT_SYMBOL_GPL(hv_get_hypervisor_version);
480
481static void __init ms_hyperv_init_platform(void)
482{
483 int hv_max_functions_eax, eax;
484
485#ifdef CONFIG_PARAVIRT
486 pv_info.name = "Hyper-V";
487#endif
488
489 /*
490 * Extract the features and hints
491 */
492 ms_hyperv.features = cpuid_eax(HYPERV_CPUID_FEATURES);
493 ms_hyperv.priv_high = cpuid_ebx(HYPERV_CPUID_FEATURES);
494 ms_hyperv.ext_features = cpuid_ecx(HYPERV_CPUID_FEATURES);
495 ms_hyperv.misc_features = cpuid_edx(HYPERV_CPUID_FEATURES);
496 ms_hyperv.hints = cpuid_eax(HYPERV_CPUID_ENLIGHTMENT_INFO);
497
498 hv_max_functions_eax = cpuid_eax(HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS);
499
500 pr_info("Hyper-V: privilege flags low %#x, high %#x, ext %#x, hints %#x, misc %#x\n",
501 ms_hyperv.features, ms_hyperv.priv_high,
502 ms_hyperv.ext_features, ms_hyperv.hints,
503 ms_hyperv.misc_features);
504
505 ms_hyperv.max_vp_index = cpuid_eax(HYPERV_CPUID_IMPLEMENT_LIMITS);
506 ms_hyperv.max_lp_index = cpuid_ebx(HYPERV_CPUID_IMPLEMENT_LIMITS);
507
508 pr_debug("Hyper-V: max %u virtual processors, %u logical processors\n",
509 ms_hyperv.max_vp_index, ms_hyperv.max_lp_index);
510
511 hv_identify_partition_type();
512
513 if (cc_platform_has(attr: CC_ATTR_SNP_SECURE_AVIC))
514 ms_hyperv.hints |= HV_DEPRECATING_AEOI_RECOMMENDED;
515
516 if (ms_hyperv.hints & HV_X64_HYPERV_NESTED) {
517 hv_nested = true;
518 pr_info("Hyper-V: running on a nested hypervisor\n");
519 }
520
521 /*
522 * There is no check against the max function for HYPERV_CPUID_VIRT_STACK_* CPUID
523 * leaves as the hypervisor doesn't handle them. Even a nested root partition (L2
524 * root) will not get them because the nested (L1) hypervisor filters them out.
525 * These are handled through intercept processing by the Windows Hyper-V stack
526 * or the paravisor.
527 */
528 eax = cpuid_eax(HYPERV_CPUID_VIRT_STACK_PROPERTIES);
529 ms_hyperv.confidential_vmbus_available =
530 eax & HYPERV_VS_PROPERTIES_EAX_CONFIDENTIAL_VMBUS_AVAILABLE;
531 ms_hyperv.msi_ext_dest_id =
532 eax & HYPERV_VS_PROPERTIES_EAX_EXTENDED_IOAPIC_RTE;
533
534 if (ms_hyperv.features & HV_ACCESS_FREQUENCY_MSRS &&
535 ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) {
536 x86_platform.calibrate_tsc = hv_get_tsc_khz;
537 x86_platform.calibrate_cpu = hv_get_tsc_khz;
538 setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
539 }
540
541 if (ms_hyperv.priv_high & HV_ISOLATION) {
542 ms_hyperv.isolation_config_a = cpuid_eax(HYPERV_CPUID_ISOLATION_CONFIG);
543 ms_hyperv.isolation_config_b = cpuid_ebx(HYPERV_CPUID_ISOLATION_CONFIG);
544
545 if (ms_hyperv.shared_gpa_boundary_active)
546 ms_hyperv.shared_gpa_boundary =
547 BIT_ULL(ms_hyperv.shared_gpa_boundary_bits);
548
549 pr_info("Hyper-V: Isolation Config: Group A 0x%x, Group B 0x%x\n",
550 ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
551
552
553 if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP) {
554 static_branch_enable(&isolation_type_snp);
555 if (!ms_hyperv.paravisor_present)
556 hypercall_update(hv_snp_hypercall);
557 } else if (hv_get_isolation_type() == HV_ISOLATION_TYPE_TDX) {
558 static_branch_enable(&isolation_type_tdx);
559
560 /* A TDX VM must use x2APIC and doesn't use lazy EOI. */
561 ms_hyperv.hints &= ~HV_X64_APIC_ACCESS_RECOMMENDED;
562
563 if (!ms_hyperv.paravisor_present) {
564 hypercall_update(hv_tdx_hypercall);
565 /*
566 * Mark the Hyper-V TSC page feature as disabled
567 * in a TDX VM without paravisor so that the
568 * Invariant TSC, which is a better clocksource
569 * anyway, is used instead.
570 */
571 ms_hyperv.features &= ~HV_MSR_REFERENCE_TSC_AVAILABLE;
572
573 /*
574 * The Invariant TSC is expected to be available
575 * in a TDX VM without paravisor, but if not,
576 * print a warning message. The slower Hyper-V MSR-based
577 * Ref Counter should end up being the clocksource.
578 */
579 if (!(ms_hyperv.features & HV_ACCESS_TSC_INVARIANT))
580 pr_warn("Hyper-V: Invariant TSC is unavailable\n");
581
582 /* HV_MSR_CRASH_CTL is unsupported. */
583 ms_hyperv.misc_features &= ~HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE;
584
585 /* Don't trust Hyper-V's TLB-flushing hypercalls. */
586 ms_hyperv.hints &= ~HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED;
587
588 x86_init.acpi.reduced_hw_early_init = reduced_hw_init;
589 }
590 }
591 }
592
593 if (hv_max_functions_eax >= HYPERV_CPUID_NESTED_FEATURES) {
594 ms_hyperv.nested_features =
595 cpuid_eax(HYPERV_CPUID_NESTED_FEATURES);
596 pr_info("Hyper-V: Nested features: 0x%x\n",
597 ms_hyperv.nested_features);
598 }
599
600#ifdef CONFIG_X86_LOCAL_APIC
601 if (ms_hyperv.features & HV_ACCESS_FREQUENCY_MSRS &&
602 ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) {
603 /*
604 * Get the APIC frequency.
605 */
606 u64 hv_lapic_frequency;
607
608 rdmsrq(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
609 hv_lapic_frequency = div_u64(dividend: hv_lapic_frequency, HZ);
610 lapic_timer_period = hv_lapic_frequency;
611 pr_info("Hyper-V: LAPIC Timer Frequency: %#x\n",
612 lapic_timer_period);
613 }
614
615 register_nmi_handler(NMI_UNKNOWN, hv_nmi_unknown, NMI_FLAG_FIRST,
616 "hv_nmi_unknown");
617#endif
618
619#ifdef CONFIG_X86_IO_APIC
620 no_timer_check = 1;
621#endif
622
623#if IS_ENABLED(CONFIG_HYPERV)
624 if (hv_root_partition())
625 machine_ops.power_off = hv_machine_power_off;
626#if defined(CONFIG_KEXEC_CORE)
627 machine_ops.shutdown = hv_machine_shutdown;
628#endif
629#if defined(CONFIG_CRASH_DUMP)
630 if (!hv_root_partition())
631 machine_ops.crash_shutdown = hv_guest_crash_shutdown;
632#endif
633#endif
634 /*
635 * HV_ACCESS_TSC_INVARIANT is always zero for the root partition. Root
636 * partition doesn't need to write to synthetic MSR to enable invariant
637 * TSC feature. It sees what the hardware provides.
638 */
639 if (ms_hyperv.features & HV_ACCESS_TSC_INVARIANT) {
640 /*
641 * Writing to synthetic MSR 0x40000118 updates/changes the
642 * guest visible CPUIDs. Setting bit 0 of this MSR enables
643 * guests to report invariant TSC feature through CPUID
644 * instruction, CPUID 0x800000007/EDX, bit 8. See code in
645 * early_init_intel() where this bit is examined. The
646 * setting of this MSR bit should happen before init_intel()
647 * is called.
648 */
649 wrmsrq(HV_X64_MSR_TSC_INVARIANT_CONTROL, HV_EXPOSE_INVARIANT_TSC);
650 setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
651 }
652
653 /*
654 * Generation 2 instances don't support reading the NMI status from
655 * 0x61 port.
656 */
657 if (efi_enabled(EFI_BOOT))
658 x86_platform.get_nmi_reason = hv_get_nmi_reason;
659
660#if IS_ENABLED(CONFIG_HYPERV)
661 if ((hv_get_isolation_type() == HV_ISOLATION_TYPE_VBS) ||
662 ms_hyperv.paravisor_present)
663 hv_vtom_init();
664 /*
665 * Setup the hook to get control post apic initialization.
666 */
667 x86_platform.apic_post_init = hyperv_init;
668 hyperv_setup_mmu_ops();
669
670 /* Install system interrupt handler for hypervisor callback */
671 sysvec_install(HYPERVISOR_CALLBACK_VECTOR, sysvec_hyperv_callback);
672
673 /* Install system interrupt handler for reenlightenment notifications */
674 if (ms_hyperv.features & HV_ACCESS_REENLIGHTENMENT) {
675 sysvec_install(HYPERV_REENLIGHTENMENT_VECTOR, sysvec_hyperv_reenlightenment);
676 }
677
678 /* Install system interrupt handler for stimer0 */
679 if (ms_hyperv.misc_features & HV_STIMER_DIRECT_MODE_AVAILABLE) {
680 sysvec_install(HYPERV_STIMER0_VECTOR, sysvec_hyperv_stimer0);
681 }
682
683# ifdef CONFIG_SMP
684 smp_ops.smp_prepare_boot_cpu = hv_smp_prepare_boot_cpu;
685 if (hv_root_partition() ||
686 (!ms_hyperv.paravisor_present && hv_isolation_type_snp()))
687 smp_ops.smp_prepare_cpus = hv_smp_prepare_cpus;
688# endif
689
690 /*
691 * Hyper-V doesn't provide irq remapping for IO-APIC. To enable x2apic,
692 * set x2apic destination mode to physical mode when x2apic is available
693 * and Hyper-V IOMMU driver makes sure cpus assigned with IO-APIC irqs
694 * have 8-bit APIC id.
695 */
696# ifdef CONFIG_X86_X2APIC
697 if (x2apic_supported())
698 x2apic_phys = 1;
699# endif
700
701 /* Register Hyper-V specific clocksource */
702 hv_init_clocksource();
703 x86_setup_ops_for_tsc_pg_clock();
704 hv_vtl_init_platform();
705#endif
706 /*
707 * TSC should be marked as unstable only after Hyper-V
708 * clocksource has been initialized. This ensures that the
709 * stability of the sched_clock is not altered.
710 *
711 * HV_ACCESS_TSC_INVARIANT is always zero for the root partition. No
712 * need to check for it.
713 */
714 if (!hv_root_partition() &&
715 !(ms_hyperv.features & HV_ACCESS_TSC_INVARIANT))
716 mark_tsc_unstable(reason: "running on Hyper-V");
717
718 hardlockup_detector_disable();
719}
720
721static bool __init ms_hyperv_x2apic_available(void)
722{
723 return x2apic_supported();
724}
725
726/*
727 * If ms_hyperv_msi_ext_dest_id() returns true, hyperv_prepare_irq_remapping()
728 * returns -ENODEV and the Hyper-V IOMMU driver is not used; instead, the
729 * generic support of the 15-bit APIC ID is used: see __irq_msi_compose_msg().
730 *
731 * Note: for a VM on Hyper-V, the I/O-APIC is the only device which
732 * (logically) generates MSIs directly to the system APIC irq domain.
733 * There is no HPET, and PCI MSI/MSI-X interrupts are remapped by the
734 * pci-hyperv host bridge.
735 *
736 * Note: for a Hyper-V root partition, this will always return false.
737 */
738static bool __init ms_hyperv_msi_ext_dest_id(void)
739{
740 return ms_hyperv.msi_ext_dest_id;
741}
742
743#ifdef CONFIG_AMD_MEM_ENCRYPT
744static void hv_sev_es_hcall_prepare(struct ghcb *ghcb, struct pt_regs *regs)
745{
746 /* RAX and CPL are already in the GHCB */
747 ghcb_set_rcx(ghcb, value: regs->cx);
748 ghcb_set_rdx(ghcb, value: regs->dx);
749 ghcb_set_r8(ghcb, value: regs->r8);
750}
751
752static bool hv_sev_es_hcall_finish(struct ghcb *ghcb, struct pt_regs *regs)
753{
754 /* No checking of the return state needed */
755 return true;
756}
757#endif
758
759const __initconst struct hypervisor_x86 x86_hyper_ms_hyperv = {
760 .name = "Microsoft Hyper-V",
761 .detect = ms_hyperv_platform,
762 .type = X86_HYPER_MS_HYPERV,
763 .init.x2apic_available = ms_hyperv_x2apic_available,
764 .init.msi_ext_dest_id = ms_hyperv_msi_ext_dest_id,
765 .init.init_platform = ms_hyperv_init_platform,
766 .init.guest_late_init = ms_hyperv_late_init,
767#ifdef CONFIG_AMD_MEM_ENCRYPT
768 .runtime.sev_es_hcall_prepare = hv_sev_es_hcall_prepare,
769 .runtime.sev_es_hcall_finish = hv_sev_es_hcall_finish,
770#endif
771};
772

source code of linux/arch/x86/kernel/cpu/mshyperv.c