/*
 * HyperV  Detection code.
 *
 * Copyright (C) 2010, Novell, Inc.
 * Author : K. Y. Srinivasan <ksrinivasan@novell.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 */

#include <linux/types.h>
#include <linux/time.h>
#include <linux/clocksource.h>
#include <linux/init.h>
#include <linux/export.h>
#include <linux/hardirq.h>
#include <linux/efi.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/kexec.h>
#include <linux/i8253.h>
#include <asm/processor.h>
#include <asm/hypervisor.h>
#include <asm/hyperv.h>
#include <asm/mshyperv.h>
#include <asm/desc.h>
#include <asm/irq_regs.h>
#include <asm/i8259.h>
#include <asm/apic.h>
#include <asm/timer.h>
#include <asm/reboot.h>
#include <asm/nmi.h>

struct ms_hyperv_info ms_hyperv;
EXPORT_SYMBOL_GPL(ms_hyperv);

#if IS_ENABLED(CONFIG_HYPERV)
static void (*vmbus_handler)(void);
static void (*hv_kexec_handler)(void);
static void (*hv_crash_handler)(struct pt_regs *regs);

void hyperv_vector_handler(struct pt_regs *regs)
{
	struct pt_regs *old_regs = set_irq_regs(regs);

	entering_irq();
	inc_irq_stat(irq_hv_callback_count);
	if (vmbus_handler)
		vmbus_handler();

	if (ms_hyperv.hints & HV_X64_DEPRECATING_AEOI_RECOMMENDED)
		ack_APIC_irq();

	exiting_irq();
	set_irq_regs(old_regs);
}

void hv_setup_vmbus_irq(void (*handler)(void))
{
	vmbus_handler = handler;
}

void hv_remove_vmbus_irq(void)
{
	/* We have no way to deallocate the interrupt gate */
	vmbus_handler = NULL;
}
EXPORT_SYMBOL_GPL(hv_setup_vmbus_irq);
EXPORT_SYMBOL_GPL(hv_remove_vmbus_irq);

void hv_setup_kexec_handler(void (*handler)(void))
{
	hv_kexec_handler = handler;
}
EXPORT_SYMBOL_GPL(hv_setup_kexec_handler);

void hv_remove_kexec_handler(void)
{
	hv_kexec_handler = NULL;
}
EXPORT_SYMBOL_GPL(hv_remove_kexec_handler);

void hv_setup_crash_handler(void (*handler)(struct pt_regs *regs))
{
	hv_crash_handler = handler;
}
EXPORT_SYMBOL_GPL(hv_setup_crash_handler);

void hv_remove_crash_handler(void)
{
	hv_crash_handler = NULL;
}
EXPORT_SYMBOL_GPL(hv_remove_crash_handler);

#ifdef CONFIG_KEXEC_CORE
static void hv_machine_shutdown(void)
{
	if (kexec_in_progress && hv_kexec_handler)
		hv_kexec_handler();
	native_machine_shutdown();
}

static void hv_machine_crash_shutdown(struct pt_regs *regs)
{
	if (hv_crash_handler)
		hv_crash_handler(regs);
	native_machine_crash_shutdown(regs);
}
#endif /* CONFIG_KEXEC_CORE */
#endif /* CONFIG_HYPERV */

static uint32_t  __init ms_hyperv_platform(void)
{
	u32 eax;
	u32 hyp_signature[3];

	if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
		return 0;

	cpuid(HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS,
	      &eax, &hyp_signature[0], &hyp_signature[1], &hyp_signature[2]);

	if (eax >= HYPERV_CPUID_MIN &&
	    eax <= HYPERV_CPUID_MAX &&
	    !memcmp("Microsoft Hv", hyp_signature, 12))
		return HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS;

	return 0;
}

static unsigned char hv_get_nmi_reason(void)
{
	return 0;
}

#ifdef CONFIG_X86_LOCAL_APIC
/*
 * Prior to WS2016 Debug-VM sends NMIs to all CPUs which makes
 * it dificult to process CHANNELMSG_UNLOAD in case of crash. Handle
 * unknown NMI on the first CPU which gets it.
 */
static int hv_nmi_unknown(unsigned int val, struct pt_regs *regs)
{
	static atomic_t nmi_cpu = ATOMIC_INIT(-1);

	if (!unknown_nmi_panic)
		return NMI_DONE;

	if (atomic_cmpxchg(&nmi_cpu, -1, raw_smp_processor_id()) != -1)
		return NMI_HANDLED;

	return NMI_DONE;
}
#endif

static unsigned long hv_get_tsc_khz(void)
{
	unsigned long freq;

	rdmsrl(HV_X64_MSR_TSC_FREQUENCY, freq);

	return freq / 1000;
}

static void __init ms_hyperv_init_platform(void)
{
	int hv_host_info_eax;
	int hv_host_info_ebx;
	int hv_host_info_ecx;
	int hv_host_info_edx;

	/*
	 * Extract the features and hints
	 */
	ms_hyperv.features = cpuid_eax(HYPERV_CPUID_FEATURES);
	ms_hyperv.misc_features = cpuid_edx(HYPERV_CPUID_FEATURES);
	ms_hyperv.hints    = cpuid_eax(HYPERV_CPUID_ENLIGHTMENT_INFO);

	pr_info("Hyper-V: features 0x%x, hints 0x%x\n",
		ms_hyperv.features, ms_hyperv.hints);

	ms_hyperv.max_vp_index = cpuid_eax(HVCPUID_IMPLEMENTATION_LIMITS);
	ms_hyperv.max_lp_index = cpuid_ebx(HVCPUID_IMPLEMENTATION_LIMITS);

	pr_debug("Hyper-V: max %u virtual processors, %u logical processors\n",
		 ms_hyperv.max_vp_index, ms_hyperv.max_lp_index);

	/*
	 * Extract host information.
	 */
	if (cpuid_eax(HVCPUID_VENDOR_MAXFUNCTION) >= HVCPUID_VERSION) {
		hv_host_info_eax = cpuid_eax(HVCPUID_VERSION);
		hv_host_info_ebx = cpuid_ebx(HVCPUID_VERSION);
		hv_host_info_ecx = cpuid_ecx(HVCPUID_VERSION);
		hv_host_info_edx = cpuid_edx(HVCPUID_VERSION);

		pr_info("Hyper-V Host Build:%d-%d.%d-%d-%d.%d\n",
			hv_host_info_eax, hv_host_info_ebx >> 16,
			hv_host_info_ebx & 0xFFFF, hv_host_info_ecx,
			hv_host_info_edx >> 24, hv_host_info_edx & 0xFFFFFF);
	}

	if (ms_hyperv.features & HV_X64_ACCESS_FREQUENCY_MSRS &&
	    ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) {
		x86_platform.calibrate_tsc = hv_get_tsc_khz;
		x86_platform.calibrate_cpu = hv_get_tsc_khz;
	}

#ifdef CONFIG_X86_LOCAL_APIC
	if (ms_hyperv.features & HV_X64_ACCESS_FREQUENCY_MSRS &&
	    ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) {
		/*
		 * Get the APIC frequency.
		 */
		u64	hv_lapic_frequency;

		rdmsrl(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
		hv_lapic_frequency = div_u64(hv_lapic_frequency, HZ);
		lapic_timer_frequency = hv_lapic_frequency;
		pr_info("Hyper-V: LAPIC Timer Frequency: %#x\n",
			lapic_timer_frequency);
	}

	register_nmi_handler(NMI_UNKNOWN, hv_nmi_unknown, NMI_FLAG_FIRST,
			     "hv_nmi_unknown");
#endif

#ifdef CONFIG_X86_IO_APIC
	no_timer_check = 1;
#endif

#if IS_ENABLED(CONFIG_HYPERV) && defined(CONFIG_KEXEC_CORE)
	machine_ops.shutdown = hv_machine_shutdown;
	machine_ops.crash_shutdown = hv_machine_crash_shutdown;
#endif
	mark_tsc_unstable("running on Hyper-V");

	/*
	 * Generation 2 instances don't support reading the NMI status from
	 * 0x61 port.
	 */
	if (efi_enabled(EFI_BOOT))
		x86_platform.get_nmi_reason = hv_get_nmi_reason;

	/*
	 * Hyper-V VMs have a PIT emulation quirk such that zeroing the
	 * counter register during PIT shutdown restarts the PIT. So it
	 * continues to interrupt @18.2 HZ. Setting i8253_clear_counter
	 * to false tells pit_shutdown() not to zero the counter so that
	 * the PIT really is shutdown. Generation 2 VMs don't have a PIT,
	 * and setting this value has no effect.
	 */
	i8253_clear_counter_on_shutdown = false;

#if IS_ENABLED(CONFIG_HYPERV)
	/*
	 * Setup the hook to get control post apic initialization.
	 */
	x86_platform.apic_post_init = hyperv_init;
	hyperv_setup_mmu_ops();
	/* Setup the IDT for hypervisor callback */
	alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR, hyperv_callback_vector);
#endif
}

const __initconst struct hypervisor_x86 x86_hyper_ms_hyperv = {
	.name			= "Microsoft Hyper-V",
	.detect			= ms_hyperv_platform,
	.type			= X86_HYPER_MS_HYPERV,
	.init.init_platform	= ms_hyperv_init_platform,
};