x86/hyperv/hv_init.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * X86 specific Hyper-V initialization code.
   4  *
   5  * Copyright (C) 2016, Microsoft, Inc.
   6  *
   7  * Author : K. Y. Srinivasan <kys@microsoft.com>
   8  */
   9
  10 #include <linux/efi.h>
  11 #include <linux/types.h>
  12 #include <linux/bitfield.h>
  13 #include <linux/io.h>
  14 #include <asm/apic.h>
  15 #include <asm/desc.h>
  16 #include <asm/e820/api.h>
  17 #include <asm/sev.h>
  18 #include <asm/ibt.h>
  19 #include <asm/hypervisor.h>
  20 #include <asm/hyperv-tlfs.h>
  21 #include <asm/mshyperv.h>
  22 #include <asm/idtentry.h>
  23 #include <linux/kexec.h>
  24 #include <linux/version.h>
  25 #include <linux/vmalloc.h>
  26 #include <linux/mm.h>
  27 #include <linux/hyperv.h>
  28 #include <linux/slab.h>
  29 #include <linux/kernel.h>
  30 #include <linux/cpuhotplug.h>
  31 #include <linux/syscore_ops.h>
  32 #include <clocksource/hyperv_timer.h>
  33 #include <linux/highmem.h>
  34 #include <linux/swiotlb.h>
  35
  36 int hyperv_init_cpuhp;
  37 u64 hv_current_partition_id = ~0ull;
  38 EXPORT_SYMBOL_GPL(hv_current_partition_id);
  39
  40 void *hv_hypercall_pg;
  41 EXPORT_SYMBOL_GPL(hv_hypercall_pg);
  42
  43 union hv_ghcb * __percpu *hv_ghcb_pg;
  44
  45 /* Storage to save the hypercall page temporarily for hibernation */
  46 static void *hv_hypercall_pg_saved;
  47
  48 struct hv_vp_assist_page **hv_vp_assist_page;
  49 EXPORT_SYMBOL_GPL(hv_vp_assist_page);
  50
  51 static int hyperv_init_ghcb(void)
  52 {
  53         u64 ghcb_gpa;
  54         void *ghcb_va;
  55         void **ghcb_base;
  56
  57         if (!hv_isolation_type_snp())
  58                 return 0;
  59
  60         if (!hv_ghcb_pg)
  61                 return -EINVAL;
  62
  63         /*
  64          * GHCB page is allocated by paravisor. The address
  65          * returned by MSR_AMD64_SEV_ES_GHCB is above shared
  66          * memory boundary and map it here.
  67          */
  68         rdmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
  69         ghcb_va = memremap(ghcb_gpa, HV_HYP_PAGE_SIZE, MEMREMAP_WB);
  70         if (!ghcb_va)
  71                 return -ENOMEM;
  72
  73         ghcb_base = (void **)this_cpu_ptr(hv_ghcb_pg);
  74         *ghcb_base = ghcb_va;
  75
  76         return 0;
  77 }
  78
  79 static int hv_cpu_init(unsigned int cpu)
  80 {
  81         union hv_vp_assist_msr_contents msr = { 0 };
  82         struct hv_vp_assist_page **hvp = &hv_vp_assist_page[cpu];
  83         int ret;
  84
  85         ret = hv_common_cpu_init(cpu);
  86         if (ret)
  87                 return ret;
  88
  89         if (!hv_vp_assist_page)
  90                 return 0;
  91
  92         if (hv_root_partition) {
  93                 /*
  94                  * For root partition we get the hypervisor provided VP assist
  95                  * page, instead of allocating a new page.
  96                  */
  97                 rdmsrl(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
  98                 *hvp = memremap(msr.pfn << HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT,
  99                                 PAGE_SIZE, MEMREMAP_WB);
 100         } else {
 101                 /*
 102                  * The VP assist page is an "overlay" page (see Hyper-V TLFS's
 103                  * Section 5.2.1 "GPA Overlay Pages"). Here it must be zeroed
 104                  * out to make sure we always write the EOI MSR in
 105                  * hv_apic_eoi_write() *after* the EOI optimization is disabled
 106                  * in hv_cpu_die(), otherwise a CPU may not be stopped in the
 107                  * case of CPU offlining and the VM will hang.
 108                  */
 109                 if (!*hvp)
 110                         *hvp = __vmalloc(PAGE_SIZE, GFP_KERNEL | __GFP_ZERO);
 111                 if (*hvp)
 112                         msr.pfn = vmalloc_to_pfn(*hvp);
 113
 114         }
 115         if (!WARN_ON(!(*hvp))) {
 116                 msr.enable = 1;
 117                 wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
 118         }
 119
 120         return hyperv_init_ghcb();
 121 }
 122
 123 static void (*hv_reenlightenment_cb)(void);
 124
 125 static void hv_reenlightenment_notify(struct work_struct *dummy)
 126 {
 127         struct hv_tsc_emulation_status emu_status;
 128
 129         rdmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, *(u64 *)&emu_status);
 130
 131         /* Don't issue the callback if TSC accesses are not emulated */
 132         if (hv_reenlightenment_cb && emu_status.inprogress)
 133                 hv_reenlightenment_cb();
 134 }
 135 static DECLARE_DELAYED_WORK(hv_reenlightenment_work, hv_reenlightenment_notify);
 136
 137 void hyperv_stop_tsc_emulation(void)
 138 {
 139         u64 freq;
 140         struct hv_tsc_emulation_status emu_status;
 141
 142         rdmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, *(u64 *)&emu_status);
 143         emu_status.inprogress = 0;
 144         wrmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, *(u64 *)&emu_status);
 145
 146         rdmsrl(HV_X64_MSR_TSC_FREQUENCY, freq);
 147         tsc_khz = div64_u64(freq, 1000);
 148 }
 149 EXPORT_SYMBOL_GPL(hyperv_stop_tsc_emulation);
 150
 151 static inline bool hv_reenlightenment_available(void)
 152 {
 153         /*
 154          * Check for required features and privileges to make TSC frequency
 155          * change notifications work.
 156          */
 157         return ms_hyperv.features & HV_ACCESS_FREQUENCY_MSRS &&
 158                 ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE &&
 159                 ms_hyperv.features & HV_ACCESS_REENLIGHTENMENT;
 160 }
 161
 162 DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_reenlightenment)
 163 {
 164         ack_APIC_irq();
 165         inc_irq_stat(irq_hv_reenlightenment_count);
 166         schedule_delayed_work(&hv_reenlightenment_work, HZ/10);
 167 }
 168
 169 void set_hv_tscchange_cb(void (*cb)(void))
 170 {
 171         struct hv_reenlightenment_control re_ctrl = {
 172                 .vector = HYPERV_REENLIGHTENMENT_VECTOR,
 173                 .enabled = 1,
 174         };
 175         struct hv_tsc_emulation_control emu_ctrl = {.enabled = 1};
 176
 177         if (!hv_reenlightenment_available()) {
 178                 pr_warn("Hyper-V: reenlightenment support is unavailable\n");
 179                 return;
 180         }
 181
 182         if (!hv_vp_index)
 183                 return;
 184
 185         hv_reenlightenment_cb = cb;
 186
 187         /* Make sure callback is registered before we write to MSRs */
 188         wmb();
 189
 190         re_ctrl.target_vp = hv_vp_index[get_cpu()];
 191
 192         wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *((u64 *)&re_ctrl));
 193         wrmsrl(HV_X64_MSR_TSC_EMULATION_CONTROL, *((u64 *)&emu_ctrl));
 194
 195         put_cpu();
 196 }
 197 EXPORT_SYMBOL_GPL(set_hv_tscchange_cb);
 198
 199 void clear_hv_tscchange_cb(void)
 200 {
 201         struct hv_reenlightenment_control re_ctrl;
 202
 203         if (!hv_reenlightenment_available())
 204                 return;
 205
 206         rdmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *(u64 *)&re_ctrl);
 207         re_ctrl.enabled = 0;
 208         wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *(u64 *)&re_ctrl);
 209
 210         hv_reenlightenment_cb = NULL;
 211 }
 212 EXPORT_SYMBOL_GPL(clear_hv_tscchange_cb);
 213
 214 static int hv_cpu_die(unsigned int cpu)
 215 {
 216         struct hv_reenlightenment_control re_ctrl;
 217         unsigned int new_cpu;
 218         void **ghcb_va;
 219
 220         if (hv_ghcb_pg) {
 221                 ghcb_va = (void **)this_cpu_ptr(hv_ghcb_pg);
 222                 if (*ghcb_va)
 223                         memunmap(*ghcb_va);
 224                 *ghcb_va = NULL;
 225         }
 226
 227         hv_common_cpu_die(cpu);
 228
 229         if (hv_vp_assist_page && hv_vp_assist_page[cpu]) {
 230                 union hv_vp_assist_msr_contents msr = { 0 };
 231                 if (hv_root_partition) {
 232                         /*
 233                          * For root partition the VP assist page is mapped to
 234                          * hypervisor provided page, and thus we unmap the
 235                          * page here and nullify it, so that in future we have
 236                          * correct page address mapped in hv_cpu_init.
 237                          */
 238                         memunmap(hv_vp_assist_page[cpu]);
 239                         hv_vp_assist_page[cpu] = NULL;
 240                         rdmsrl(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
 241                         msr.enable = 0;
 242                 }
 243                 wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
 244         }
 245
 246         if (hv_reenlightenment_cb == NULL)
 247                 return 0;
 248
 249         rdmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *((u64 *)&re_ctrl));
 250         if (re_ctrl.target_vp == hv_vp_index[cpu]) {
 251                 /*
 252                  * Reassign reenlightenment notifications to some other online
 253                  * CPU or just disable the feature if there are no online CPUs
 254                  * left (happens on hibernation).
 255                  */
 256                 new_cpu = cpumask_any_but(cpu_online_mask, cpu);
 257
 258                 if (new_cpu < nr_cpu_ids)
 259                         re_ctrl.target_vp = hv_vp_index[new_cpu];
 260                 else
 261                         re_ctrl.enabled = 0;
 262
 263                 wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *((u64 *)&re_ctrl));
 264         }
 265
 266         return 0;
 267 }
 268
 269 static int __init hv_pci_init(void)
 270 {
 271         bool gen2vm = efi_enabled(EFI_BOOT);
 272
 273         /*
 274          * A Generation-2 VM doesn't support legacy PCI/PCIe, so both
 275          * raw_pci_ops and raw_pci_ext_ops are NULL, and pci_subsys_init() ->
 276          * pcibios_init() doesn't call pcibios_resource_survey() ->
 277          * e820__reserve_resources_late(); as a result, any emulated persistent
 278          * memory of E820_TYPE_PRAM (12) via the kernel parameter
 279          * memmap=nn[KMG]!ss is not added into iomem_resource and hence can't be
 280          * detected by register_e820_pmem(). Fix this by directly calling
 281          * e820__reserve_resources_late() here: e820__reserve_resources_late()
 282          * depends on e820__reserve_resources(), which has been called earlier
 283          * from setup_arch(). Note: e820__reserve_resources_late() also adds
 284          * any memory of E820_TYPE_PMEM (7) into iomem_resource, and
 285          * acpi_nfit_register_region() -> acpi_nfit_insert_resource() ->
 286          * region_intersects() returns REGION_INTERSECTS, so the memory of
 287          * E820_TYPE_PMEM won't get added twice.
 288          *
 289          * We return 0 here so that pci_arch_init() won't print the warning:
 290          * "PCI: Fatal: No config space access function found"
 291          */
 292         if (gen2vm) {
 293                 e820__reserve_resources_late();
 294                 return 0;
 295         }
 296
 297         /* For Generation-1 VM, we'll proceed in pci_arch_init().  */
 298         return 1;
 299 }
 300
 301 static int hv_suspend(void)
 302 {
 303         union hv_x64_msr_hypercall_contents hypercall_msr;
 304         int ret;
 305
 306         if (hv_root_partition)
 307                 return -EPERM;
 308
 309         /*
 310          * Reset the hypercall page as it is going to be invalidated
 311          * across hibernation. Setting hv_hypercall_pg to NULL ensures
 312          * that any subsequent hypercall operation fails safely instead of
 313          * crashing due to an access of an invalid page. The hypercall page
 314          * pointer is restored on resume.
 315          */
 316         hv_hypercall_pg_saved = hv_hypercall_pg;
 317         hv_hypercall_pg = NULL;
 318
 319         /* Disable the hypercall page in the hypervisor */
 320         rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
 321         hypercall_msr.enable = 0;
 322         wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
 323
 324         ret = hv_cpu_die(0);
 325         return ret;
 326 }
 327
 328 static void hv_resume(void)
 329 {
 330         union hv_x64_msr_hypercall_contents hypercall_msr;
 331         int ret;
 332
 333         ret = hv_cpu_init(0);
 334         WARN_ON(ret);
 335
 336         /* Re-enable the hypercall page */
 337         rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
 338         hypercall_msr.enable = 1;
 339         hypercall_msr.guest_physical_address =
 340                 vmalloc_to_pfn(hv_hypercall_pg_saved);
 341         wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
 342
 343         hv_hypercall_pg = hv_hypercall_pg_saved;
 344         hv_hypercall_pg_saved = NULL;
 345
 346         /*
 347          * Reenlightenment notifications are disabled by hv_cpu_die(0),
 348          * reenable them here if hv_reenlightenment_cb was previously set.
 349          */
 350         if (hv_reenlightenment_cb)
 351                 set_hv_tscchange_cb(hv_reenlightenment_cb);
 352 }
 353
 354 /* Note: when the ops are called, only CPU0 is online and IRQs are disabled. */
 355 static struct syscore_ops hv_syscore_ops = {
 356         .suspend        = hv_suspend,
 357         .resume         = hv_resume,
 358 };
 359
 360 static void (* __initdata old_setup_percpu_clockev)(void);
 361
 362 static void __init hv_stimer_setup_percpu_clockev(void)
 363 {
 364         /*
 365          * Ignore any errors in setting up stimer clockevents
 366          * as we can run with the LAPIC timer as a fallback.
 367          */
 368         (void)hv_stimer_alloc(false);
 369
 370         /*
 371          * Still register the LAPIC timer, because the direct-mode STIMER is
 372          * not supported by old versions of Hyper-V. This also allows users
 373          * to switch to LAPIC timer via /sys, if they want to.
 374          */
 375         if (old_setup_percpu_clockev)
 376                 old_setup_percpu_clockev();
 377 }
 378
 379 static void __init hv_get_partition_id(void)
 380 {
 381         struct hv_get_partition_id *output_page;
 382         u64 status;
 383         unsigned long flags;
 384
 385         local_irq_save(flags);
 386         output_page = *this_cpu_ptr(hyperv_pcpu_output_arg);
 387         status = hv_do_hypercall(HVCALL_GET_PARTITION_ID, NULL, output_page);
 388         if (!hv_result_success(status)) {
 389                 /* No point in proceeding if this failed */
 390                 pr_err("Failed to get partition ID: %lld\n", status);
 391                 BUG();
 392         }
 393         hv_current_partition_id = output_page->partition_id;
 394         local_irq_restore(flags);
 395 }
 396
 397 /*
 398  * This function is to be invoked early in the boot sequence after the
 399  * hypervisor has been detected.
 400  *
 401  * 1. Setup the hypercall page.
 402  * 2. Register Hyper-V specific clocksource.
 403  * 3. Setup Hyper-V specific APIC entry points.
 404  */
 405 void __init hyperv_init(void)
 406 {
 407         u64 guest_id;
 408         union hv_x64_msr_hypercall_contents hypercall_msr;
 409         int cpuhp;
 410
 411         if (x86_hyper_type != X86_HYPER_MS_HYPERV)
 412                 return;
 413
 414         if (hv_common_init())
 415                 return;
 416
 417         hv_vp_assist_page = kcalloc(num_possible_cpus(),
 418                                     sizeof(*hv_vp_assist_page), GFP_KERNEL);
 419         if (!hv_vp_assist_page) {
 420                 ms_hyperv.hints &= ~HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
 421                 goto common_free;
 422         }
 423
 424         if (hv_isolation_type_snp()) {
 425                 /* Negotiate GHCB Version. */
 426                 if (!hv_ghcb_negotiate_protocol())
 427                         hv_ghcb_terminate(SEV_TERM_SET_GEN,
 428                                           GHCB_SEV_ES_PROT_UNSUPPORTED);
 429
 430                 hv_ghcb_pg = alloc_percpu(union hv_ghcb *);
 431                 if (!hv_ghcb_pg)
 432                         goto free_vp_assist_page;
 433         }
 434
 435         cpuhp = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/hyperv_init:online",
 436                                   hv_cpu_init, hv_cpu_die);
 437         if (cpuhp < 0)
 438                 goto free_ghcb_page;
 439
 440         /*
 441          * Setup the hypercall page and enable hypercalls.
 442          * 1. Register the guest ID
 443          * 2. Enable the hypercall and register the hypercall page
 444          */
 445         guest_id = hv_generate_guest_id(LINUX_VERSION_CODE);
 446         wrmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id);
 447
 448         /* Hyper-V requires to write guest os id via ghcb in SNP IVM. */
 449         hv_ghcb_msr_write(HV_X64_MSR_GUEST_OS_ID, guest_id);
 450
 451         hv_hypercall_pg = __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START,
 452                         VMALLOC_END, GFP_KERNEL, PAGE_KERNEL_ROX,
 453                         VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
 454                         __builtin_return_address(0));
 455         if (hv_hypercall_pg == NULL)
 456                 goto clean_guest_os_id;
 457
 458         rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
 459         hypercall_msr.enable = 1;
 460
 461         if (hv_root_partition) {
 462                 struct page *pg;
 463                 void *src;
 464
 465                 /*
 466                  * For the root partition, the hypervisor will set up its
 467                  * hypercall page. The hypervisor guarantees it will not show
 468                  * up in the root's address space. The root can't change the
 469                  * location of the hypercall page.
 470                  *
 471                  * Order is important here. We must enable the hypercall page
 472                  * so it is populated with code, then copy the code to an
 473                  * executable page.
 474                  */
 475                 wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
 476
 477                 pg = vmalloc_to_page(hv_hypercall_pg);
 478                 src = memremap(hypercall_msr.guest_physical_address << PAGE_SHIFT, PAGE_SIZE,
 479                                 MEMREMAP_WB);
 480                 BUG_ON(!src);
 481                 memcpy_to_page(pg, 0, src, HV_HYP_PAGE_SIZE);
 482                 memunmap(src);
 483         } else {
 484                 hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
 485                 wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
 486         }
 487
 488         /*
 489          * Some versions of Hyper-V that provide IBT in guest VMs have a bug
 490          * in that there's no ENDBR64 instruction at the entry to the
 491          * hypercall page. Because hypercalls are invoked via an indirect call
 492          * to the hypercall page, all hypercall attempts fail when IBT is
 493          * enabled, and Linux panics. For such buggy versions, disable IBT.
 494          *
 495          * Fixed versions of Hyper-V always provide ENDBR64 on the hypercall
 496          * page, so if future Linux kernel versions enable IBT for 32-bit
 497          * builds, additional hypercall page hackery will be required here
 498          * to provide an ENDBR32.
 499          */
 500 #ifdef CONFIG_X86_KERNEL_IBT
 501         if (cpu_feature_enabled(X86_FEATURE_IBT) &&
 502             *(u32 *)hv_hypercall_pg != gen_endbr()) {
 503                 setup_clear_cpu_cap(X86_FEATURE_IBT);
 504                 pr_warn("Hyper-V: Disabling IBT because of Hyper-V bug\n");
 505         }
 506 #endif
 507
 508         /*
 509          * hyperv_init() is called before LAPIC is initialized: see
 510          * apic_intr_mode_init() -> x86_platform.apic_post_init() and
 511          * apic_bsp_setup() -> setup_local_APIC(). The direct-mode STIMER
 512          * depends on LAPIC, so hv_stimer_alloc() should be called from
 513          * x86_init.timers.setup_percpu_clockev.
 514          */
 515         old_setup_percpu_clockev = x86_init.timers.setup_percpu_clockev;
 516         x86_init.timers.setup_percpu_clockev = hv_stimer_setup_percpu_clockev;
 517
 518         hv_apic_init();
 519
 520         x86_init.pci.arch_init = hv_pci_init;
 521
 522         register_syscore_ops(&hv_syscore_ops);
 523
 524         hyperv_init_cpuhp = cpuhp;
 525
 526         if (cpuid_ebx(HYPERV_CPUID_FEATURES) & HV_ACCESS_PARTITION_ID)
 527                 hv_get_partition_id();
 528
 529         BUG_ON(hv_root_partition && hv_current_partition_id == ~0ull);
 530
 531 #ifdef CONFIG_PCI_MSI
 532         /*
 533          * If we're running as root, we want to create our own PCI MSI domain.
 534          * We can't set this in hv_pci_init because that would be too late.
 535          */
 536         if (hv_root_partition)
 537                 x86_init.irqs.create_pci_msi_domain = hv_create_pci_msi_domain;
 538 #endif
 539
 540         /* Query the VMs extended capability once, so that it can be cached. */
 541         hv_query_ext_cap(0);
 542
 543 #ifdef CONFIG_SWIOTLB
 544         /*
 545          * Swiotlb bounce buffer needs to be mapped in extra address
 546          * space. Map function doesn't work in the early place and so
 547          * call swiotlb_update_mem_attributes() here.
 548          */
 549         if (hv_is_isolation_supported())
 550                 swiotlb_update_mem_attributes();
 551 #endif
 552
 553         return;
 554
 555 clean_guest_os_id:
 556         wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
 557         hv_ghcb_msr_write(HV_X64_MSR_GUEST_OS_ID, 0);
 558         cpuhp_remove_state(cpuhp);
 559 free_ghcb_page:
 560         free_percpu(hv_ghcb_pg);
 561 free_vp_assist_page:
 562         kfree(hv_vp_assist_page);
 563         hv_vp_assist_page = NULL;
 564 common_free:
 565         hv_common_free();
 566 }
 567
 568 /*
 569  * This routine is called before kexec/kdump, it does the required cleanup.
 570  */
 571 void hyperv_cleanup(void)
 572 {
 573         union hv_x64_msr_hypercall_contents hypercall_msr;
 574         union hv_reference_tsc_msr tsc_msr;
 575
 576         /* Reset our OS id */
 577         wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
 578         hv_ghcb_msr_write(HV_X64_MSR_GUEST_OS_ID, 0);
 579
 580         /*
 581          * Reset hypercall page reference before reset the page,
 582          * let hypercall operations fail safely rather than
 583          * panic the kernel for using invalid hypercall page
 584          */
 585         hv_hypercall_pg = NULL;
 586
 587         /* Reset the hypercall page */
 588         hypercall_msr.as_uint64 = hv_get_register(HV_X64_MSR_HYPERCALL);
 589         hypercall_msr.enable = 0;
 590         hv_set_register(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
 591
 592         /* Reset the TSC page */
 593         tsc_msr.as_uint64 = hv_get_register(HV_X64_MSR_REFERENCE_TSC);
 594         tsc_msr.enable = 0;
 595         hv_set_register(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
 596 }
 597
 598 void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die)
 599 {
 600         static bool panic_reported;
 601         u64 guest_id;
 602
 603         if (in_die && !panic_on_oops)
 604                 return;
 605
 606         /*
 607          * We prefer to report panic on 'die' chain as we have proper
 608          * registers to report, but if we miss it (e.g. on BUG()) we need
 609          * to report it on 'panic'.
 610          */
 611         if (panic_reported)
 612                 return;
 613         panic_reported = true;
 614
 615         rdmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id);
 616
 617         wrmsrl(HV_X64_MSR_CRASH_P0, err);
 618         wrmsrl(HV_X64_MSR_CRASH_P1, guest_id);
 619         wrmsrl(HV_X64_MSR_CRASH_P2, regs->ip);
 620         wrmsrl(HV_X64_MSR_CRASH_P3, regs->ax);
 621         wrmsrl(HV_X64_MSR_CRASH_P4, regs->sp);
 622
 623         /*
 624          * Let Hyper-V know there is crash data available
 625          */
 626         wrmsrl(HV_X64_MSR_CRASH_CTL, HV_CRASH_CTL_CRASH_NOTIFY);
 627 }
 628 EXPORT_SYMBOL_GPL(hyperv_report_panic);
 629
 630 bool hv_is_hyperv_initialized(void)
 631 {
 632         union hv_x64_msr_hypercall_contents hypercall_msr;
 633
 634         /*
 635          * Ensure that we're really on Hyper-V, and not a KVM or Xen
 636          * emulation of Hyper-V
 637          */
 638         if (x86_hyper_type != X86_HYPER_MS_HYPERV)
 639                 return false;
 640
 641         /*
 642          * Verify that earlier initialization succeeded by checking
 643          * that the hypercall page is setup
 644          */
 645         hypercall_msr.as_uint64 = 0;
 646         rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
 647
 648         return hypercall_msr.enable;
 649 }
 650 EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized);