Merge tag 'icc-6.7-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/djakov/icc...
[linux-2.6-microblaze.git] / arch / x86 / kernel / cpu / mshyperv.c
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/i8253.h>
20 #include <linux/random.h>
21 #include <asm/processor.h>
22 #include <asm/hypervisor.h>
23 #include <asm/hyperv-tlfs.h>
24 #include <asm/mshyperv.h>
25 #include <asm/desc.h>
26 #include <asm/idtentry.h>
27 #include <asm/irq_regs.h>
28 #include <asm/i8259.h>
29 #include <asm/apic.h>
30 #include <asm/timer.h>
31 #include <asm/reboot.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 as the root partition? */
38 bool hv_root_partition;
39 /* Is Linux running on nested Microsoft Hypervisor */
40 bool hv_nested;
41 struct ms_hyperv_info ms_hyperv;
42
43 /* Used in modules via hv_do_hypercall(): see arch/x86/include/asm/mshyperv.h */
44 bool hyperv_paravisor_present __ro_after_init;
45 EXPORT_SYMBOL_GPL(hyperv_paravisor_present);
46
47 #if IS_ENABLED(CONFIG_HYPERV)
48 static inline unsigned int hv_get_nested_reg(unsigned int reg)
49 {
50         if (hv_is_sint_reg(reg))
51                 return reg - HV_REGISTER_SINT0 + HV_REGISTER_NESTED_SINT0;
52
53         switch (reg) {
54         case HV_REGISTER_SIMP:
55                 return HV_REGISTER_NESTED_SIMP;
56         case HV_REGISTER_SIEFP:
57                 return HV_REGISTER_NESTED_SIEFP;
58         case HV_REGISTER_SVERSION:
59                 return HV_REGISTER_NESTED_SVERSION;
60         case HV_REGISTER_SCONTROL:
61                 return HV_REGISTER_NESTED_SCONTROL;
62         case HV_REGISTER_EOM:
63                 return HV_REGISTER_NESTED_EOM;
64         default:
65                 return reg;
66         }
67 }
68
69 u64 hv_get_non_nested_register(unsigned int reg)
70 {
71         u64 value;
72
73         if (hv_is_synic_reg(reg) && ms_hyperv.paravisor_present)
74                 hv_ivm_msr_read(reg, &value);
75         else
76                 rdmsrl(reg, value);
77         return value;
78 }
79 EXPORT_SYMBOL_GPL(hv_get_non_nested_register);
80
81 void hv_set_non_nested_register(unsigned int reg, u64 value)
82 {
83         if (hv_is_synic_reg(reg) && ms_hyperv.paravisor_present) {
84                 hv_ivm_msr_write(reg, value);
85
86                 /* Write proxy bit via wrmsl instruction */
87                 if (hv_is_sint_reg(reg))
88                         wrmsrl(reg, value | 1 << 20);
89         } else {
90                 wrmsrl(reg, value);
91         }
92 }
93 EXPORT_SYMBOL_GPL(hv_set_non_nested_register);
94
95 u64 hv_get_register(unsigned int reg)
96 {
97         if (hv_nested)
98                 reg = hv_get_nested_reg(reg);
99
100         return hv_get_non_nested_register(reg);
101 }
102 EXPORT_SYMBOL_GPL(hv_get_register);
103
104 void hv_set_register(unsigned int reg, u64 value)
105 {
106         if (hv_nested)
107                 reg = hv_get_nested_reg(reg);
108
109         hv_set_non_nested_register(reg, value);
110 }
111 EXPORT_SYMBOL_GPL(hv_set_register);
112
113 static void (*vmbus_handler)(void);
114 static void (*hv_stimer0_handler)(void);
115 static void (*hv_kexec_handler)(void);
116 static void (*hv_crash_handler)(struct pt_regs *regs);
117
118 DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_callback)
119 {
120         struct pt_regs *old_regs = set_irq_regs(regs);
121
122         inc_irq_stat(irq_hv_callback_count);
123         if (vmbus_handler)
124                 vmbus_handler();
125
126         if (ms_hyperv.hints & HV_DEPRECATING_AEOI_RECOMMENDED)
127                 apic_eoi();
128
129         set_irq_regs(old_regs);
130 }
131
132 void hv_setup_vmbus_handler(void (*handler)(void))
133 {
134         vmbus_handler = handler;
135 }
136
137 void hv_remove_vmbus_handler(void)
138 {
139         /* We have no way to deallocate the interrupt gate */
140         vmbus_handler = NULL;
141 }
142
143 /*
144  * Routines to do per-architecture handling of stimer0
145  * interrupts when in Direct Mode
146  */
147 DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_stimer0)
148 {
149         struct pt_regs *old_regs = set_irq_regs(regs);
150
151         inc_irq_stat(hyperv_stimer0_count);
152         if (hv_stimer0_handler)
153                 hv_stimer0_handler();
154         add_interrupt_randomness(HYPERV_STIMER0_VECTOR);
155         apic_eoi();
156
157         set_irq_regs(old_regs);
158 }
159
160 /* For x86/x64, override weak placeholders in hyperv_timer.c */
161 void hv_setup_stimer0_handler(void (*handler)(void))
162 {
163         hv_stimer0_handler = handler;
164 }
165
166 void hv_remove_stimer0_handler(void)
167 {
168         /* We have no way to deallocate the interrupt gate */
169         hv_stimer0_handler = NULL;
170 }
171
172 void hv_setup_kexec_handler(void (*handler)(void))
173 {
174         hv_kexec_handler = handler;
175 }
176
177 void hv_remove_kexec_handler(void)
178 {
179         hv_kexec_handler = NULL;
180 }
181
182 void hv_setup_crash_handler(void (*handler)(struct pt_regs *regs))
183 {
184         hv_crash_handler = handler;
185 }
186
187 void hv_remove_crash_handler(void)
188 {
189         hv_crash_handler = NULL;
190 }
191
192 #ifdef CONFIG_KEXEC_CORE
193 static void hv_machine_shutdown(void)
194 {
195         if (kexec_in_progress && hv_kexec_handler)
196                 hv_kexec_handler();
197
198         /*
199          * Call hv_cpu_die() on all the CPUs, otherwise later the hypervisor
200          * corrupts the old VP Assist Pages and can crash the kexec kernel.
201          */
202         if (kexec_in_progress && hyperv_init_cpuhp > 0)
203                 cpuhp_remove_state(hyperv_init_cpuhp);
204
205         /* The function calls stop_other_cpus(). */
206         native_machine_shutdown();
207
208         /* Disable the hypercall page when there is only 1 active CPU. */
209         if (kexec_in_progress)
210                 hyperv_cleanup();
211 }
212
213 static void hv_machine_crash_shutdown(struct pt_regs *regs)
214 {
215         if (hv_crash_handler)
216                 hv_crash_handler(regs);
217
218         /* The function calls crash_smp_send_stop(). */
219         native_machine_crash_shutdown(regs);
220
221         /* Disable the hypercall page when there is only 1 active CPU. */
222         hyperv_cleanup();
223 }
224 #endif /* CONFIG_KEXEC_CORE */
225 #endif /* CONFIG_HYPERV */
226
227 static uint32_t  __init ms_hyperv_platform(void)
228 {
229         u32 eax;
230         u32 hyp_signature[3];
231
232         if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
233                 return 0;
234
235         cpuid(HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS,
236               &eax, &hyp_signature[0], &hyp_signature[1], &hyp_signature[2]);
237
238         if (eax < HYPERV_CPUID_MIN || eax > HYPERV_CPUID_MAX ||
239             memcmp("Microsoft Hv", hyp_signature, 12))
240                 return 0;
241
242         /* HYPERCALL and VP_INDEX MSRs are mandatory for all features. */
243         eax = cpuid_eax(HYPERV_CPUID_FEATURES);
244         if (!(eax & HV_MSR_HYPERCALL_AVAILABLE)) {
245                 pr_warn("x86/hyperv: HYPERCALL MSR not available.\n");
246                 return 0;
247         }
248         if (!(eax & HV_MSR_VP_INDEX_AVAILABLE)) {
249                 pr_warn("x86/hyperv: VP_INDEX MSR not available.\n");
250                 return 0;
251         }
252
253         return HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS;
254 }
255
256 #ifdef CONFIG_X86_LOCAL_APIC
257 /*
258  * Prior to WS2016 Debug-VM sends NMIs to all CPUs which makes
259  * it difficult to process CHANNELMSG_UNLOAD in case of crash. Handle
260  * unknown NMI on the first CPU which gets it.
261  */
262 static int hv_nmi_unknown(unsigned int val, struct pt_regs *regs)
263 {
264         static atomic_t nmi_cpu = ATOMIC_INIT(-1);
265         unsigned int old_cpu, this_cpu;
266
267         if (!unknown_nmi_panic)
268                 return NMI_DONE;
269
270         old_cpu = -1;
271         this_cpu = raw_smp_processor_id();
272         if (!atomic_try_cmpxchg(&nmi_cpu, &old_cpu, this_cpu))
273                 return NMI_HANDLED;
274
275         return NMI_DONE;
276 }
277 #endif
278
279 static unsigned long hv_get_tsc_khz(void)
280 {
281         unsigned long freq;
282
283         rdmsrl(HV_X64_MSR_TSC_FREQUENCY, freq);
284
285         return freq / 1000;
286 }
287
288 #if defined(CONFIG_SMP) && IS_ENABLED(CONFIG_HYPERV)
289 static void __init hv_smp_prepare_boot_cpu(void)
290 {
291         native_smp_prepare_boot_cpu();
292 #if defined(CONFIG_X86_64) && defined(CONFIG_PARAVIRT_SPINLOCKS)
293         hv_init_spinlocks();
294 #endif
295 }
296
297 static void __init hv_smp_prepare_cpus(unsigned int max_cpus)
298 {
299 #ifdef CONFIG_X86_64
300         int i;
301         int ret;
302 #endif
303
304         native_smp_prepare_cpus(max_cpus);
305
306         /*
307          *  Override wakeup_secondary_cpu_64 callback for SEV-SNP
308          *  enlightened guest.
309          */
310         if (!ms_hyperv.paravisor_present && hv_isolation_type_snp()) {
311                 apic->wakeup_secondary_cpu_64 = hv_snp_boot_ap;
312                 return;
313         }
314
315 #ifdef CONFIG_X86_64
316         for_each_present_cpu(i) {
317                 if (i == 0)
318                         continue;
319                 ret = hv_call_add_logical_proc(numa_cpu_node(i), i, cpu_physical_id(i));
320                 BUG_ON(ret);
321         }
322
323         for_each_present_cpu(i) {
324                 if (i == 0)
325                         continue;
326                 ret = hv_call_create_vp(numa_cpu_node(i), hv_current_partition_id, i, i);
327                 BUG_ON(ret);
328         }
329 #endif
330 }
331 #endif
332
333 /*
334  * When a fully enlightened TDX VM runs on Hyper-V, the firmware sets the
335  * HW_REDUCED flag: refer to acpi_tb_create_local_fadt(). Consequently ttyS0
336  * interrupts can't work because request_irq() -> ... -> irq_to_desc() returns
337  * NULL for ttyS0. This happens because mp_config_acpi_legacy_irqs() sees a
338  * nr_legacy_irqs() of 0, so it doesn't initialize the array 'mp_irqs[]', and
339  * later setup_IO_APIC_irqs() -> find_irq_entry() fails to find the legacy irqs
340  * from the array and hence doesn't create the necessary irq description info.
341  *
342  * Clone arch/x86/kernel/acpi/boot.c: acpi_generic_reduced_hw_init() here,
343  * except don't change 'legacy_pic', which keeps its default value
344  * 'default_legacy_pic'. This way, mp_config_acpi_legacy_irqs() sees a non-zero
345  * nr_legacy_irqs() and eventually serial console interrupts works properly.
346  */
347 static void __init reduced_hw_init(void)
348 {
349         x86_init.timers.timer_init      = x86_init_noop;
350         x86_init.irqs.pre_vector_init   = x86_init_noop;
351 }
352
353 static void __init ms_hyperv_init_platform(void)
354 {
355         int hv_max_functions_eax;
356         int hv_host_info_eax;
357         int hv_host_info_ebx;
358         int hv_host_info_ecx;
359         int hv_host_info_edx;
360
361 #ifdef CONFIG_PARAVIRT
362         pv_info.name = "Hyper-V";
363 #endif
364
365         /*
366          * Extract the features and hints
367          */
368         ms_hyperv.features = cpuid_eax(HYPERV_CPUID_FEATURES);
369         ms_hyperv.priv_high = cpuid_ebx(HYPERV_CPUID_FEATURES);
370         ms_hyperv.misc_features = cpuid_edx(HYPERV_CPUID_FEATURES);
371         ms_hyperv.hints    = cpuid_eax(HYPERV_CPUID_ENLIGHTMENT_INFO);
372
373         hv_max_functions_eax = cpuid_eax(HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS);
374
375         pr_info("Hyper-V: privilege flags low 0x%x, high 0x%x, hints 0x%x, misc 0x%x\n",
376                 ms_hyperv.features, ms_hyperv.priv_high, ms_hyperv.hints,
377                 ms_hyperv.misc_features);
378
379         ms_hyperv.max_vp_index = cpuid_eax(HYPERV_CPUID_IMPLEMENT_LIMITS);
380         ms_hyperv.max_lp_index = cpuid_ebx(HYPERV_CPUID_IMPLEMENT_LIMITS);
381
382         pr_debug("Hyper-V: max %u virtual processors, %u logical processors\n",
383                  ms_hyperv.max_vp_index, ms_hyperv.max_lp_index);
384
385         /*
386          * Check CPU management privilege.
387          *
388          * To mirror what Windows does we should extract CPU management
389          * features and use the ReservedIdentityBit to detect if Linux is the
390          * root partition. But that requires negotiating CPU management
391          * interface (a process to be finalized). For now, use the privilege
392          * flag as the indicator for running as root.
393          *
394          * Hyper-V should never specify running as root and as a Confidential
395          * VM. But to protect against a compromised/malicious Hyper-V trying
396          * to exploit root behavior to expose Confidential VM memory, ignore
397          * the root partition setting if also a Confidential VM.
398          */
399         if ((ms_hyperv.priv_high & HV_CPU_MANAGEMENT) &&
400             !(ms_hyperv.priv_high & HV_ISOLATION)) {
401                 hv_root_partition = true;
402                 pr_info("Hyper-V: running as root partition\n");
403         }
404
405         if (ms_hyperv.hints & HV_X64_HYPERV_NESTED) {
406                 hv_nested = true;
407                 pr_info("Hyper-V: running on a nested hypervisor\n");
408         }
409
410         /*
411          * Extract host information.
412          */
413         if (hv_max_functions_eax >= HYPERV_CPUID_VERSION) {
414                 hv_host_info_eax = cpuid_eax(HYPERV_CPUID_VERSION);
415                 hv_host_info_ebx = cpuid_ebx(HYPERV_CPUID_VERSION);
416                 hv_host_info_ecx = cpuid_ecx(HYPERV_CPUID_VERSION);
417                 hv_host_info_edx = cpuid_edx(HYPERV_CPUID_VERSION);
418
419                 pr_info("Hyper-V: Host Build %d.%d.%d.%d-%d-%d\n",
420                         hv_host_info_ebx >> 16, hv_host_info_ebx & 0xFFFF,
421                         hv_host_info_eax, hv_host_info_edx & 0xFFFFFF,
422                         hv_host_info_ecx, hv_host_info_edx >> 24);
423         }
424
425         if (ms_hyperv.features & HV_ACCESS_FREQUENCY_MSRS &&
426             ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) {
427                 x86_platform.calibrate_tsc = hv_get_tsc_khz;
428                 x86_platform.calibrate_cpu = hv_get_tsc_khz;
429         }
430
431         if (ms_hyperv.priv_high & HV_ISOLATION) {
432                 ms_hyperv.isolation_config_a = cpuid_eax(HYPERV_CPUID_ISOLATION_CONFIG);
433                 ms_hyperv.isolation_config_b = cpuid_ebx(HYPERV_CPUID_ISOLATION_CONFIG);
434
435                 if (ms_hyperv.shared_gpa_boundary_active)
436                         ms_hyperv.shared_gpa_boundary =
437                                 BIT_ULL(ms_hyperv.shared_gpa_boundary_bits);
438
439                 hyperv_paravisor_present = !!ms_hyperv.paravisor_present;
440
441                 pr_info("Hyper-V: Isolation Config: Group A 0x%x, Group B 0x%x\n",
442                         ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
443
444
445                 if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP) {
446                         static_branch_enable(&isolation_type_snp);
447                 } else if (hv_get_isolation_type() == HV_ISOLATION_TYPE_TDX) {
448                         static_branch_enable(&isolation_type_tdx);
449
450                         /* A TDX VM must use x2APIC and doesn't use lazy EOI. */
451                         ms_hyperv.hints &= ~HV_X64_APIC_ACCESS_RECOMMENDED;
452
453                         if (!ms_hyperv.paravisor_present) {
454                                 /* To be supported: more work is required.  */
455                                 ms_hyperv.features &= ~HV_MSR_REFERENCE_TSC_AVAILABLE;
456
457                                 /* HV_REGISTER_CRASH_CTL is unsupported. */
458                                 ms_hyperv.misc_features &= ~HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE;
459
460                                 /* Don't trust Hyper-V's TLB-flushing hypercalls. */
461                                 ms_hyperv.hints &= ~HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED;
462
463                                 x86_init.acpi.reduced_hw_early_init = reduced_hw_init;
464                         }
465                 }
466         }
467
468         if (hv_max_functions_eax >= HYPERV_CPUID_NESTED_FEATURES) {
469                 ms_hyperv.nested_features =
470                         cpuid_eax(HYPERV_CPUID_NESTED_FEATURES);
471                 pr_info("Hyper-V: Nested features: 0x%x\n",
472                         ms_hyperv.nested_features);
473         }
474
475 #ifdef CONFIG_X86_LOCAL_APIC
476         if (ms_hyperv.features & HV_ACCESS_FREQUENCY_MSRS &&
477             ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) {
478                 /*
479                  * Get the APIC frequency.
480                  */
481                 u64     hv_lapic_frequency;
482
483                 rdmsrl(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
484                 hv_lapic_frequency = div_u64(hv_lapic_frequency, HZ);
485                 lapic_timer_period = hv_lapic_frequency;
486                 pr_info("Hyper-V: LAPIC Timer Frequency: %#x\n",
487                         lapic_timer_period);
488         }
489
490         register_nmi_handler(NMI_UNKNOWN, hv_nmi_unknown, NMI_FLAG_FIRST,
491                              "hv_nmi_unknown");
492 #endif
493
494 #ifdef CONFIG_X86_IO_APIC
495         no_timer_check = 1;
496 #endif
497
498 #if IS_ENABLED(CONFIG_HYPERV) && defined(CONFIG_KEXEC_CORE)
499         machine_ops.shutdown = hv_machine_shutdown;
500         machine_ops.crash_shutdown = hv_machine_crash_shutdown;
501 #endif
502         if (ms_hyperv.features & HV_ACCESS_TSC_INVARIANT) {
503                 /*
504                  * Writing to synthetic MSR 0x40000118 updates/changes the
505                  * guest visible CPUIDs. Setting bit 0 of this MSR  enables
506                  * guests to report invariant TSC feature through CPUID
507                  * instruction, CPUID 0x800000007/EDX, bit 8. See code in
508                  * early_init_intel() where this bit is examined. The
509                  * setting of this MSR bit should happen before init_intel()
510                  * is called.
511                  */
512                 wrmsrl(HV_X64_MSR_TSC_INVARIANT_CONTROL, HV_EXPOSE_INVARIANT_TSC);
513                 setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
514         }
515
516         /*
517          * Generation 2 instances don't support reading the NMI status from
518          * 0x61 port.
519          */
520         if (efi_enabled(EFI_BOOT))
521                 x86_platform.get_nmi_reason = hv_get_nmi_reason;
522
523         /*
524          * Hyper-V VMs have a PIT emulation quirk such that zeroing the
525          * counter register during PIT shutdown restarts the PIT. So it
526          * continues to interrupt @18.2 HZ. Setting i8253_clear_counter
527          * to false tells pit_shutdown() not to zero the counter so that
528          * the PIT really is shutdown. Generation 2 VMs don't have a PIT,
529          * and setting this value has no effect.
530          */
531         i8253_clear_counter_on_shutdown = false;
532
533 #if IS_ENABLED(CONFIG_HYPERV)
534         if ((hv_get_isolation_type() == HV_ISOLATION_TYPE_VBS) ||
535             ms_hyperv.paravisor_present)
536                 hv_vtom_init();
537         /*
538          * Setup the hook to get control post apic initialization.
539          */
540         x86_platform.apic_post_init = hyperv_init;
541         hyperv_setup_mmu_ops();
542         /* Setup the IDT for hypervisor callback */
543         alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR, asm_sysvec_hyperv_callback);
544
545         /* Setup the IDT for reenlightenment notifications */
546         if (ms_hyperv.features & HV_ACCESS_REENLIGHTENMENT) {
547                 alloc_intr_gate(HYPERV_REENLIGHTENMENT_VECTOR,
548                                 asm_sysvec_hyperv_reenlightenment);
549         }
550
551         /* Setup the IDT for stimer0 */
552         if (ms_hyperv.misc_features & HV_STIMER_DIRECT_MODE_AVAILABLE) {
553                 alloc_intr_gate(HYPERV_STIMER0_VECTOR,
554                                 asm_sysvec_hyperv_stimer0);
555         }
556
557 # ifdef CONFIG_SMP
558         smp_ops.smp_prepare_boot_cpu = hv_smp_prepare_boot_cpu;
559         if (hv_root_partition ||
560             (!ms_hyperv.paravisor_present && hv_isolation_type_snp()))
561                 smp_ops.smp_prepare_cpus = hv_smp_prepare_cpus;
562 # endif
563
564         /*
565          * Hyper-V doesn't provide irq remapping for IO-APIC. To enable x2apic,
566          * set x2apic destination mode to physical mode when x2apic is available
567          * and Hyper-V IOMMU driver makes sure cpus assigned with IO-APIC irqs
568          * have 8-bit APIC id.
569          */
570 # ifdef CONFIG_X86_X2APIC
571         if (x2apic_supported())
572                 x2apic_phys = 1;
573 # endif
574
575         /* Register Hyper-V specific clocksource */
576         hv_init_clocksource();
577         hv_vtl_init_platform();
578 #endif
579         /*
580          * TSC should be marked as unstable only after Hyper-V
581          * clocksource has been initialized. This ensures that the
582          * stability of the sched_clock is not altered.
583          */
584         if (!(ms_hyperv.features & HV_ACCESS_TSC_INVARIANT))
585                 mark_tsc_unstable("running on Hyper-V");
586
587         hardlockup_detector_disable();
588 }
589
590 static bool __init ms_hyperv_x2apic_available(void)
591 {
592         return x2apic_supported();
593 }
594
595 /*
596  * If ms_hyperv_msi_ext_dest_id() returns true, hyperv_prepare_irq_remapping()
597  * returns -ENODEV and the Hyper-V IOMMU driver is not used; instead, the
598  * generic support of the 15-bit APIC ID is used: see __irq_msi_compose_msg().
599  *
600  * Note: for a VM on Hyper-V, the I/O-APIC is the only device which
601  * (logically) generates MSIs directly to the system APIC irq domain.
602  * There is no HPET, and PCI MSI/MSI-X interrupts are remapped by the
603  * pci-hyperv host bridge.
604  *
605  * Note: for a Hyper-V root partition, this will always return false.
606  * The hypervisor doesn't expose these HYPERV_CPUID_VIRT_STACK_* cpuids by
607  * default, they are implemented as intercepts by the Windows Hyper-V stack.
608  * Even a nested root partition (L2 root) will not get them because the
609  * nested (L1) hypervisor filters them out.
610  */
611 static bool __init ms_hyperv_msi_ext_dest_id(void)
612 {
613         u32 eax;
614
615         eax = cpuid_eax(HYPERV_CPUID_VIRT_STACK_INTERFACE);
616         if (eax != HYPERV_VS_INTERFACE_EAX_SIGNATURE)
617                 return false;
618
619         eax = cpuid_eax(HYPERV_CPUID_VIRT_STACK_PROPERTIES);
620         return eax & HYPERV_VS_PROPERTIES_EAX_EXTENDED_IOAPIC_RTE;
621 }
622
623 #ifdef CONFIG_AMD_MEM_ENCRYPT
624 static void hv_sev_es_hcall_prepare(struct ghcb *ghcb, struct pt_regs *regs)
625 {
626         /* RAX and CPL are already in the GHCB */
627         ghcb_set_rcx(ghcb, regs->cx);
628         ghcb_set_rdx(ghcb, regs->dx);
629         ghcb_set_r8(ghcb, regs->r8);
630 }
631
632 static bool hv_sev_es_hcall_finish(struct ghcb *ghcb, struct pt_regs *regs)
633 {
634         /* No checking of the return state needed */
635         return true;
636 }
637 #endif
638
639 const __initconst struct hypervisor_x86 x86_hyper_ms_hyperv = {
640         .name                   = "Microsoft Hyper-V",
641         .detect                 = ms_hyperv_platform,
642         .type                   = X86_HYPER_MS_HYPERV,
643         .init.x2apic_available  = ms_hyperv_x2apic_available,
644         .init.msi_ext_dest_id   = ms_hyperv_msi_ext_dest_id,
645         .init.init_platform     = ms_hyperv_init_platform,
646 #ifdef CONFIG_AMD_MEM_ENCRYPT
647         .runtime.sev_es_hcall_prepare = hv_sev_es_hcall_prepare,
648         .runtime.sev_es_hcall_finish = hv_sev_es_hcall_finish,
649 #endif
650 };