arch/x86/hyperv/hv_init.c - linux/torvalds/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * X86 specific Hyper-V initialization code.
  *
  * Copyright (C) 2016, Microsoft, Inc.
  *
  * Author : K. Y. Srinivasan <kys@microsoft.com>
  */

 #include <linux/efi.h>
 #include <linux/types.h>
 #include <asm/apic.h>
 #include <asm/desc.h>
 #include <asm/hypervisor.h>
 #include <asm/hyperv-tlfs.h>
 #include <asm/mshyperv.h>
 #include <linux/version.h>
 #include <linux/vmalloc.h>
 #include <linux/mm.h>
 #include <linux/hyperv.h>
 #include <linux/slab.h>
 #include <linux/cpuhotplug.h>
 #include <clocksource/hyperv_timer.h>

 void *hv_hypercall_pg;
 EXPORT_SYMBOL_GPL(hv_hypercall_pg);

 u32 *hv_vp_index;
 EXPORT_SYMBOL_GPL(hv_vp_index);

 struct hv_vp_assist_page **hv_vp_assist_page;
 EXPORT_SYMBOL_GPL(hv_vp_assist_page);

 void  __percpu **hyperv_pcpu_input_arg;
 EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);

 u32 hv_max_vp_index;
 EXPORT_SYMBOL_GPL(hv_max_vp_index);

 static int hv_cpu_init(unsigned int cpu)
 {
 	u64 msr_vp_index;
 	struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
 	void **input_arg;
 	struct page *pg;

 	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
 	pg = alloc_page(GFP_KERNEL);
 	if (unlikely(!pg))
 		return -ENOMEM;
 	*input_arg = page_address(pg);

 	hv_get_vp_index(msr_vp_index);

 	hv_vp_index[smp_processor_id()] = msr_vp_index;

 	if (msr_vp_index > hv_max_vp_index)
 		hv_max_vp_index = msr_vp_index;

 	if (!hv_vp_assist_page)
 		return 0;

 	/*
 	 * The VP ASSIST PAGE is an "overlay" page (see Hyper-V TLFS's Section
 	 * 5.2.1 "GPA Overlay Pages"). Here it must be zeroed out to make sure
 	 * we always write the EOI MSR in hv_apic_eoi_write() *after* the
 	 * EOI optimization is disabled in hv_cpu_die(), otherwise a CPU may
 	 * not be stopped in the case of CPU offlining and the VM will hang.
 	 */
 	if (!*hvp) {
 		*hvp = __vmalloc(PAGE_SIZE, GFP_KERNEL | __GFP_ZERO,
 				 PAGE_KERNEL);
 	}

 	if (*hvp) {
 		u64 val;

 		val = vmalloc_to_pfn(*hvp);
 		val = (val << HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT) |
 			HV_X64_MSR_VP_ASSIST_PAGE_ENABLE;

 		wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, val);
 	}

 	return 0;
 }

 static void (*hv_reenlightenment_cb)(void);

 static void hv_reenlightenment_notify(struct work_struct *dummy)
 {
 	struct hv_tsc_emulation_status emu_status;

 	rdmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, *(u64 *)&emu_status);

 	/* Don't issue the callback if TSC accesses are not emulated */
 	if (hv_reenlightenment_cb && emu_status.inprogress)
 		hv_reenlightenment_cb();
 }
 static DECLARE_DELAYED_WORK(hv_reenlightenment_work, hv_reenlightenment_notify);

 void hyperv_stop_tsc_emulation(void)
 {
 	u64 freq;
 	struct hv_tsc_emulation_status emu_status;

 	rdmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, *(u64 *)&emu_status);
 	emu_status.inprogress = 0;
 	wrmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, *(u64 *)&emu_status);

 	rdmsrl(HV_X64_MSR_TSC_FREQUENCY, freq);
 	tsc_khz = div64_u64(freq, 1000);
 }
 EXPORT_SYMBOL_GPL(hyperv_stop_tsc_emulation);

 static inline bool hv_reenlightenment_available(void)
 {
 	/*
 	 * Check for required features and priviliges to make TSC frequency
 	 * change notifications work.
 	 */
 	return ms_hyperv.features & HV_X64_ACCESS_FREQUENCY_MSRS &&
 		ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE &&
 		ms_hyperv.features & HV_X64_ACCESS_REENLIGHTENMENT;
 }

 __visible void __irq_entry hyperv_reenlightenment_intr(struct pt_regs *regs)
 {
 	entering_ack_irq();

 	inc_irq_stat(irq_hv_reenlightenment_count);

 	schedule_delayed_work(&hv_reenlightenment_work, HZ/10);

 	exiting_irq();
 }

 void set_hv_tscchange_cb(void (*cb)(void))
 {
 	struct hv_reenlightenment_control re_ctrl = {
 		.vector = HYPERV_REENLIGHTENMENT_VECTOR,
 		.enabled = 1,
 		.target_vp = hv_vp_index[smp_processor_id()]
 	};
 	struct hv_tsc_emulation_control emu_ctrl = {.enabled = 1};

 	if (!hv_reenlightenment_available()) {
 		pr_warn("Hyper-V: reenlightenment support is unavailable\n");
 		return;
 	}

 	hv_reenlightenment_cb = cb;

 	/* Make sure callback is registered before we write to MSRs */
 	wmb();

 	wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *((u64 *)&re_ctrl));
 	wrmsrl(HV_X64_MSR_TSC_EMULATION_CONTROL, *((u64 *)&emu_ctrl));
 }
 EXPORT_SYMBOL_GPL(set_hv_tscchange_cb);

 void clear_hv_tscchange_cb(void)
 {
 	struct hv_reenlightenment_control re_ctrl;

 	if (!hv_reenlightenment_available())
 		return;

 	rdmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *(u64 *)&re_ctrl);
 	re_ctrl.enabled = 0;
 	wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *(u64 *)&re_ctrl);

 	hv_reenlightenment_cb = NULL;
 }
 EXPORT_SYMBOL_GPL(clear_hv_tscchange_cb);

 static int hv_cpu_die(unsigned int cpu)
 {
 	struct hv_reenlightenment_control re_ctrl;
 	unsigned int new_cpu;
 	unsigned long flags;
 	void **input_arg;
 	void *input_pg = NULL;

 	local_irq_save(flags);
 	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
 	input_pg = *input_arg;
 	*input_arg = NULL;
 	local_irq_restore(flags);
 	free_page((unsigned long)input_pg);

 	if (hv_vp_assist_page && hv_vp_assist_page[cpu])
 		wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, 0);

 	if (hv_reenlightenment_cb == NULL)
 		return 0;

 	rdmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *((u64 *)&re_ctrl));
 	if (re_ctrl.target_vp == hv_vp_index[cpu]) {
 		/* Reassign to some other online CPU */
 		new_cpu = cpumask_any_but(cpu_online_mask, cpu);

 		re_ctrl.target_vp = hv_vp_index[new_cpu];
 		wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *((u64 *)&re_ctrl));
 	}

 	return 0;
 }

 static int __init hv_pci_init(void)
 {
 	int gen2vm = efi_enabled(EFI_BOOT);

 	/*
 	 * For Generation-2 VM, we exit from pci_arch_init() by returning 0.
 	 * The purpose is to suppress the harmless warning:
 	 * "PCI: Fatal: No config space access function found"
 	 */
 	if (gen2vm)
 		return 0;

 	/* For Generation-1 VM, we'll proceed in pci_arch_init().  */
 	return 1;
 }

 /*
  * This function is to be invoked early in the boot sequence after the
  * hypervisor has been detected.
  *
  * 1. Setup the hypercall page.
  * 2. Register Hyper-V specific clocksource.
  * 3. Setup Hyper-V specific APIC entry points.
  */
 void __init hyperv_init(void)
 {
 	u64 guest_id, required_msrs;
 	union hv_x64_msr_hypercall_contents hypercall_msr;
 	int cpuhp, i;

 	if (x86_hyper_type != X86_HYPER_MS_HYPERV)
 		return;

 	/* Absolutely required MSRs */
 	required_msrs = HV_X64_MSR_HYPERCALL_AVAILABLE |
 		HV_X64_MSR_VP_INDEX_AVAILABLE;

 	if ((ms_hyperv.features & required_msrs) != required_msrs)
 		return;

 	/*
 	 * Allocate the per-CPU state for the hypercall input arg.
 	 * If this allocation fails, we will not be able to setup
 	 * (per-CPU) hypercall input page and thus this failure is
 	 * fatal on Hyper-V.
 	 */
 	hyperv_pcpu_input_arg = alloc_percpu(void  *);

 	BUG_ON(hyperv_pcpu_input_arg == NULL);

 	/* Allocate percpu VP index */
 	hv_vp_index = kmalloc_array(num_possible_cpus(), sizeof(*hv_vp_index),
 				    GFP_KERNEL);
 	if (!hv_vp_index)
 		return;

 	for (i = 0; i < num_possible_cpus(); i++)
 		hv_vp_index[i] = VP_INVAL;

 	hv_vp_assist_page = kcalloc(num_possible_cpus(),
 				    sizeof(*hv_vp_assist_page), GFP_KERNEL);
 	if (!hv_vp_assist_page) {
 		ms_hyperv.hints &= ~HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
 		goto free_vp_index;
 	}

 	cpuhp = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/hyperv_init:online",
 				  hv_cpu_init, hv_cpu_die);
 	if (cpuhp < 0)
 		goto free_vp_assist_page;

 	/*
 	 * Setup the hypercall page and enable hypercalls.
 	 * 1. Register the guest ID
 	 * 2. Enable the hypercall and register the hypercall page
 	 */
 	guest_id = generate_guest_id(0, LINUX_VERSION_CODE, 0);
 	wrmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id);

 	hv_hypercall_pg  = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL_RX);
 	if (hv_hypercall_pg == NULL) {
 		wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
 		goto remove_cpuhp_state;
 	}

 	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
 	hypercall_msr.enable = 1;
 	hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
 	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);

 	hv_apic_init();

 	x86_init.pci.arch_init = hv_pci_init;

 	/* Register Hyper-V specific clocksource */
 	hv_init_clocksource();
 	return;

 remove_cpuhp_state:
 	cpuhp_remove_state(cpuhp);
 free_vp_assist_page:
 	kfree(hv_vp_assist_page);
 	hv_vp_assist_page = NULL;
 free_vp_index:
 	kfree(hv_vp_index);
 	hv_vp_index = NULL;
 }

 /*
  * This routine is called before kexec/kdump, it does the required cleanup.
  */
 void hyperv_cleanup(void)
 {
 	union hv_x64_msr_hypercall_contents hypercall_msr;

 	/* Reset our OS id */
 	wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);

 	/*
 	 * Reset hypercall page reference before reset the page,
 	 * let hypercall operations fail safely rather than
 	 * panic the kernel for using invalid hypercall page
 	 */
 	hv_hypercall_pg = NULL;

 	/* Reset the hypercall page */
 	hypercall_msr.as_uint64 = 0;
 	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);

 	/* Reset the TSC page */
 	hypercall_msr.as_uint64 = 0;
 	wrmsrl(HV_X64_MSR_REFERENCE_TSC, hypercall_msr.as_uint64);
 }
 EXPORT_SYMBOL_GPL(hyperv_cleanup);

 void hyperv_report_panic(struct pt_regs *regs, long err)
 {
 	static bool panic_reported;
 	u64 guest_id;

 	/*
 	 * We prefer to report panic on 'die' chain as we have proper
 	 * registers to report, but if we miss it (e.g. on BUG()) we need
 	 * to report it on 'panic'.
 	 */
 	if (panic_reported)
 		return;
 	panic_reported = true;

 	rdmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id);

 	wrmsrl(HV_X64_MSR_CRASH_P0, err);
 	wrmsrl(HV_X64_MSR_CRASH_P1, guest_id);
 	wrmsrl(HV_X64_MSR_CRASH_P2, regs->ip);
 	wrmsrl(HV_X64_MSR_CRASH_P3, regs->ax);
 	wrmsrl(HV_X64_MSR_CRASH_P4, regs->sp);

 	/*
 	 * Let Hyper-V know there is crash data available
 	 */
 	wrmsrl(HV_X64_MSR_CRASH_CTL, HV_CRASH_CTL_CRASH_NOTIFY);
 }
 EXPORT_SYMBOL_GPL(hyperv_report_panic);

 /**
  * hyperv_report_panic_msg - report panic message to Hyper-V
  * @pa: physical address of the panic page containing the message
  * @size: size of the message in the page
  */
 void hyperv_report_panic_msg(phys_addr_t pa, size_t size)
 {
 	/*
 	 * P3 to contain the physical address of the panic page & P4 to
 	 * contain the size of the panic data in that page. Rest of the
 	 * registers are no-op when the NOTIFY_MSG flag is set.
 	 */
 	wrmsrl(HV_X64_MSR_CRASH_P0, 0);
 	wrmsrl(HV_X64_MSR_CRASH_P1, 0);
 	wrmsrl(HV_X64_MSR_CRASH_P2, 0);
 	wrmsrl(HV_X64_MSR_CRASH_P3, pa);
 	wrmsrl(HV_X64_MSR_CRASH_P4, size);

 	/*
 	 * Let Hyper-V know there is crash data available along with
 	 * the panic message.
 	 */
 	wrmsrl(HV_X64_MSR_CRASH_CTL,
 	       (HV_CRASH_CTL_CRASH_NOTIFY | HV_CRASH_CTL_CRASH_NOTIFY_MSG));
 }
 EXPORT_SYMBOL_GPL(hyperv_report_panic_msg);

 bool hv_is_hyperv_initialized(void)
 {
 	union hv_x64_msr_hypercall_contents hypercall_msr;

 	/*
 	 * Ensure that we're really on Hyper-V, and not a KVM or Xen
 	 * emulation of Hyper-V
 	 */
 	if (x86_hyper_type != X86_HYPER_MS_HYPERV)
 		return false;

 	/*
 	 * Verify that earlier initialization succeeded by checking
 	 * that the hypercall page is setup
 	 */
 	hypercall_msr.as_uint64 = 0;
 	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);

 	return hypercall_msr.enable;
 }
 EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized);
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* X86 specific Hyper-V initialization code.
	*
	* Copyright (C) 2016, Microsoft, Inc.
	*
	* Author : K. Y. Srinivasan <kys@microsoft.com>
	*/

	#include <linux/efi.h>
	#include <linux/types.h>
	#include <asm/apic.h>
	#include <asm/desc.h>
	#include <asm/hypervisor.h>
	#include <asm/hyperv-tlfs.h>
	#include <asm/mshyperv.h>
	#include <linux/version.h>
	#include <linux/vmalloc.h>
	#include <linux/mm.h>
	#include <linux/hyperv.h>
	#include <linux/slab.h>
	#include <linux/cpuhotplug.h>
	#include <clocksource/hyperv_timer.h>

	void *hv_hypercall_pg;
	EXPORT_SYMBOL_GPL(hv_hypercall_pg);

	u32 *hv_vp_index;
	EXPORT_SYMBOL_GPL(hv_vp_index);

	struct hv_vp_assist_page **hv_vp_assist_page;
	EXPORT_SYMBOL_GPL(hv_vp_assist_page);

	void __percpu **hyperv_pcpu_input_arg;
	EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);

	u32 hv_max_vp_index;
	EXPORT_SYMBOL_GPL(hv_max_vp_index);

	static int hv_cpu_init(unsigned int cpu)
	{
	u64 msr_vp_index;
	struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
	void **input_arg;
	struct page *pg;

	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
	pg = alloc_page(GFP_KERNEL);
	if (unlikely(!pg))
	return -ENOMEM;
	*input_arg = page_address(pg);

	hv_get_vp_index(msr_vp_index);

	hv_vp_index[smp_processor_id()] = msr_vp_index;

	if (msr_vp_index > hv_max_vp_index)
	hv_max_vp_index = msr_vp_index;

	if (!hv_vp_assist_page)
	return 0;

	/*
	* The VP ASSIST PAGE is an "overlay" page (see Hyper-V TLFS's Section
	* 5.2.1 "GPA Overlay Pages"). Here it must be zeroed out to make sure
	* we always write the EOI MSR in hv_apic_eoi_write() after the
	* EOI optimization is disabled in hv_cpu_die(), otherwise a CPU may
	* not be stopped in the case of CPU offlining and the VM will hang.
	*/
	if (!*hvp) {
	*hvp = __vmalloc(PAGE_SIZE, GFP_KERNEL \| __GFP_ZERO,
	PAGE_KERNEL);
	}

	if (*hvp) {
	u64 val;

	val = vmalloc_to_pfn(*hvp);
	val = (val << HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT) \|
	HV_X64_MSR_VP_ASSIST_PAGE_ENABLE;

	wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, val);
	}

	return 0;
	}

	static void (*hv_reenlightenment_cb)(void);

	static void hv_reenlightenment_notify(struct work_struct *dummy)
	{
	struct hv_tsc_emulation_status emu_status;

	rdmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, (u64 )&emu_status);

	/* Don't issue the callback if TSC accesses are not emulated */
	if (hv_reenlightenment_cb && emu_status.inprogress)
	hv_reenlightenment_cb();
	}
	static DECLARE_DELAYED_WORK(hv_reenlightenment_work, hv_reenlightenment_notify);

	void hyperv_stop_tsc_emulation(void)
	{
	u64 freq;
	struct hv_tsc_emulation_status emu_status;

	rdmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, (u64 )&emu_status);
	emu_status.inprogress = 0;
	wrmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, (u64 )&emu_status);

	rdmsrl(HV_X64_MSR_TSC_FREQUENCY, freq);
	tsc_khz = div64_u64(freq, 1000);
	}
	EXPORT_SYMBOL_GPL(hyperv_stop_tsc_emulation);

	static inline bool hv_reenlightenment_available(void)
	{
	/*
	* Check for required features and priviliges to make TSC frequency
	* change notifications work.
	*/
	return ms_hyperv.features & HV_X64_ACCESS_FREQUENCY_MSRS &&
	ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE &&
	ms_hyperv.features & HV_X64_ACCESS_REENLIGHTENMENT;
	}

	__visible void __irq_entry hyperv_reenlightenment_intr(struct pt_regs *regs)
	{
	entering_ack_irq();

	inc_irq_stat(irq_hv_reenlightenment_count);

	schedule_delayed_work(&hv_reenlightenment_work, HZ/10);

	exiting_irq();
	}

	void set_hv_tscchange_cb(void (*cb)(void))
	{
	struct hv_reenlightenment_control re_ctrl = {
	.vector = HYPERV_REENLIGHTENMENT_VECTOR,
	.enabled = 1,
	.target_vp = hv_vp_index[smp_processor_id()]
	};
	struct hv_tsc_emulation_control emu_ctrl = {.enabled = 1};

	if (!hv_reenlightenment_available()) {
	pr_warn("Hyper-V: reenlightenment support is unavailable\n");
	return;
	}

	hv_reenlightenment_cb = cb;

	/* Make sure callback is registered before we write to MSRs */
	wmb();

	wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, ((u64 )&re_ctrl));
	wrmsrl(HV_X64_MSR_TSC_EMULATION_CONTROL, ((u64 )&emu_ctrl));
	}
	EXPORT_SYMBOL_GPL(set_hv_tscchange_cb);

	void clear_hv_tscchange_cb(void)
	{
	struct hv_reenlightenment_control re_ctrl;

	if (!hv_reenlightenment_available())
	return;

	rdmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, (u64 )&re_ctrl);
	re_ctrl.enabled = 0;
	wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, (u64 )&re_ctrl);

	hv_reenlightenment_cb = NULL;
	}
	EXPORT_SYMBOL_GPL(clear_hv_tscchange_cb);

	static int hv_cpu_die(unsigned int cpu)
	{
	struct hv_reenlightenment_control re_ctrl;
	unsigned int new_cpu;
	unsigned long flags;
	void **input_arg;
	void *input_pg = NULL;

	local_irq_save(flags);
	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
	input_pg = *input_arg;
	*input_arg = NULL;
	local_irq_restore(flags);
	free_page((unsigned long)input_pg);

	if (hv_vp_assist_page && hv_vp_assist_page[cpu])
	wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, 0);

	if (hv_reenlightenment_cb == NULL)
	return 0;

	rdmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, ((u64 )&re_ctrl));
	if (re_ctrl.target_vp == hv_vp_index[cpu]) {
	/* Reassign to some other online CPU */
	new_cpu = cpumask_any_but(cpu_online_mask, cpu);

	re_ctrl.target_vp = hv_vp_index[new_cpu];
	wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, ((u64 )&re_ctrl));
	}

	return 0;
	}

	static int __init hv_pci_init(void)
	{
	int gen2vm = efi_enabled(EFI_BOOT);

	/*
	* For Generation-2 VM, we exit from pci_arch_init() by returning 0.
	* The purpose is to suppress the harmless warning:
	* "PCI: Fatal: No config space access function found"
	*/
	if (gen2vm)
	return 0;

	/* For Generation-1 VM, we'll proceed in pci_arch_init(). */
	return 1;
	}

	/*
	* This function is to be invoked early in the boot sequence after the
	* hypervisor has been detected.
	*
	* 1. Setup the hypercall page.
	* 2. Register Hyper-V specific clocksource.
	* 3. Setup Hyper-V specific APIC entry points.
	*/
	void __init hyperv_init(void)
	{
	u64 guest_id, required_msrs;
	union hv_x64_msr_hypercall_contents hypercall_msr;
	int cpuhp, i;

	if (x86_hyper_type != X86_HYPER_MS_HYPERV)
	return;

	/* Absolutely required MSRs */
	required_msrs = HV_X64_MSR_HYPERCALL_AVAILABLE \|
	HV_X64_MSR_VP_INDEX_AVAILABLE;

	if ((ms_hyperv.features & required_msrs) != required_msrs)
	return;

	/*
	* Allocate the per-CPU state for the hypercall input arg.
	* If this allocation fails, we will not be able to setup
	* (per-CPU) hypercall input page and thus this failure is
	* fatal on Hyper-V.
	*/
	hyperv_pcpu_input_arg = alloc_percpu(void *);

	BUG_ON(hyperv_pcpu_input_arg == NULL);

	/* Allocate percpu VP index */
	hv_vp_index = kmalloc_array(num_possible_cpus(), sizeof(*hv_vp_index),
	GFP_KERNEL);
	if (!hv_vp_index)
	return;

	for (i = 0; i < num_possible_cpus(); i++)
	hv_vp_index[i] = VP_INVAL;

	hv_vp_assist_page = kcalloc(num_possible_cpus(),
	sizeof(*hv_vp_assist_page), GFP_KERNEL);
	if (!hv_vp_assist_page) {
	ms_hyperv.hints &= ~HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
	goto free_vp_index;
	}

	cpuhp = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/hyperv_init:online",
	hv_cpu_init, hv_cpu_die);
	if (cpuhp < 0)
	goto free_vp_assist_page;

	/*
	* Setup the hypercall page and enable hypercalls.
	* 1. Register the guest ID
	* 2. Enable the hypercall and register the hypercall page
	*/
	guest_id = generate_guest_id(0, LINUX_VERSION_CODE, 0);
	wrmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id);

	hv_hypercall_pg = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL_RX);
	if (hv_hypercall_pg == NULL) {
	wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
	goto remove_cpuhp_state;
	}

	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
	hypercall_msr.enable = 1;
	hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);

	hv_apic_init();

	x86_init.pci.arch_init = hv_pci_init;

	/* Register Hyper-V specific clocksource */
	hv_init_clocksource();
	return;

	remove_cpuhp_state:
	cpuhp_remove_state(cpuhp);
	free_vp_assist_page:
	kfree(hv_vp_assist_page);
	hv_vp_assist_page = NULL;
	free_vp_index:
	kfree(hv_vp_index);
	hv_vp_index = NULL;
	}

	/*
	* This routine is called before kexec/kdump, it does the required cleanup.
	*/
	void hyperv_cleanup(void)
	{
	union hv_x64_msr_hypercall_contents hypercall_msr;

	/* Reset our OS id */
	wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);

	/*
	* Reset hypercall page reference before reset the page,
	* let hypercall operations fail safely rather than
	* panic the kernel for using invalid hypercall page
	*/
	hv_hypercall_pg = NULL;

	/* Reset the hypercall page */
	hypercall_msr.as_uint64 = 0;
	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);

	/* Reset the TSC page */
	hypercall_msr.as_uint64 = 0;
	wrmsrl(HV_X64_MSR_REFERENCE_TSC, hypercall_msr.as_uint64);
	}
	EXPORT_SYMBOL_GPL(hyperv_cleanup);

	void hyperv_report_panic(struct pt_regs *regs, long err)
	{
	static bool panic_reported;
	u64 guest_id;

	/*
	* We prefer to report panic on 'die' chain as we have proper
	* registers to report, but if we miss it (e.g. on BUG()) we need
	* to report it on 'panic'.
	*/
	if (panic_reported)
	return;
	panic_reported = true;

	rdmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id);

	wrmsrl(HV_X64_MSR_CRASH_P0, err);
	wrmsrl(HV_X64_MSR_CRASH_P1, guest_id);
	wrmsrl(HV_X64_MSR_CRASH_P2, regs->ip);
	wrmsrl(HV_X64_MSR_CRASH_P3, regs->ax);
	wrmsrl(HV_X64_MSR_CRASH_P4, regs->sp);

	/*
	* Let Hyper-V know there is crash data available
	*/
	wrmsrl(HV_X64_MSR_CRASH_CTL, HV_CRASH_CTL_CRASH_NOTIFY);
	}
	EXPORT_SYMBOL_GPL(hyperv_report_panic);

	/**
	* hyperv_report_panic_msg - report panic message to Hyper-V
	* @pa: physical address of the panic page containing the message
	* @size: size of the message in the page
	*/
	void hyperv_report_panic_msg(phys_addr_t pa, size_t size)
	{
	/*
	* P3 to contain the physical address of the panic page & P4 to
	* contain the size of the panic data in that page. Rest of the
	* registers are no-op when the NOTIFY_MSG flag is set.
	*/
	wrmsrl(HV_X64_MSR_CRASH_P0, 0);
	wrmsrl(HV_X64_MSR_CRASH_P1, 0);
	wrmsrl(HV_X64_MSR_CRASH_P2, 0);
	wrmsrl(HV_X64_MSR_CRASH_P3, pa);
	wrmsrl(HV_X64_MSR_CRASH_P4, size);

	/*
	* Let Hyper-V know there is crash data available along with
	* the panic message.
	*/
	wrmsrl(HV_X64_MSR_CRASH_CTL,
	(HV_CRASH_CTL_CRASH_NOTIFY \| HV_CRASH_CTL_CRASH_NOTIFY_MSG));
	}
	EXPORT_SYMBOL_GPL(hyperv_report_panic_msg);

	bool hv_is_hyperv_initialized(void)
	{
	union hv_x64_msr_hypercall_contents hypercall_msr;

	/*
	* Ensure that we're really on Hyper-V, and not a KVM or Xen
	* emulation of Hyper-V
	*/
	if (x86_hyper_type != X86_HYPER_MS_HYPERV)
	return false;

	/*
	* Verify that earlier initialization succeeded by checking
	* that the hypercall page is setup
	*/
	hypercall_msr.as_uint64 = 0;
	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);

	return hypercall_msr.enable;
	}
	EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized);