/*
 * KVM paravirt_ops implementation
 *
 * 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; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * Copyright (C) 2007, Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 * Copyright IBM Corporation, 2007
 *   Authors: Anthony Liguori <aliguori@us.ibm.com>
 */

#include <linux/context_tracking.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/kvm_para.h>
#include <linux/cpu.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/hardirq.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/hash.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/kprobes.h>
#include <linux/debugfs.h>
#include <linux/nmi.h>
#include <linux/swait.h>
#include <asm/timer.h>
#include <asm/cpu.h>
#include <asm/traps.h>
#include <asm/desc.h>
#include <asm/tlbflush.h>
#include <asm/apic.h>
#include <asm/apicdef.h>
#include <asm/hypervisor.h>
#include <asm/kvm_guest.h>

static int kvmapf = 1;

static int __init parse_no_kvmapf(char *arg)
{
        kvmapf = 0;
        return 0;
}

early_param("no-kvmapf", parse_no_kvmapf);

static int steal_acc = 1;
static int __init parse_no_stealacc(char *arg)
{
        steal_acc = 0;
        return 0;
}

early_param("no-steal-acc", parse_no_stealacc);

static int kvmclock_vsyscall = 1;
static int __init parse_no_kvmclock_vsyscall(char *arg)
{
        kvmclock_vsyscall = 0;
        return 0;
}

early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall);

static DEFINE_PER_CPU_DECRYPTED(struct kvm_vcpu_pv_apf_data, apf_reason) __aligned(64);
static DEFINE_PER_CPU_DECRYPTED(struct kvm_steal_time, steal_time) __aligned(64);
static int has_steal_clock = 0;

/*
 * No need for any "IO delay" on KVM
 */
static void kvm_io_delay(void)
{
}

#define KVM_TASK_SLEEP_HASHBITS 8
#define KVM_TASK_SLEEP_HASHSIZE (1<<KVM_TASK_SLEEP_HASHBITS)

struct kvm_task_sleep_node {
        struct hlist_node link;
        struct swait_queue_head wq;
        u32 token;
        int cpu;
        bool halted;
};

static struct kvm_task_sleep_head {
        raw_spinlock_t lock;
        struct hlist_head list;
} async_pf_sleepers[KVM_TASK_SLEEP_HASHSIZE];

static struct kvm_task_sleep_node *_find_apf_task(struct kvm_task_sleep_head *b,
                                                  u32 token)
{
        struct hlist_node *p;

        hlist_for_each(p, &b->list) {
                struct kvm_task_sleep_node *n =
                        hlist_entry(p, typeof(*n), link);
                if (n->token == token)
                        return n;
        }

        return NULL;
}

/*
 * @interrupt_kernel: Is this called from a routine which interrupts the kernel
 *                    (other than user space)?
 */
void kvm_async_pf_task_wait(u32 token, int interrupt_kernel)
{
        u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
        struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
        struct kvm_task_sleep_node n, *e;
        DECLARE_SWAITQUEUE(wait);

        rcu_irq_enter();

        raw_spin_lock(&b->lock);
        e = _find_apf_task(b, token);
        if (e) {
                /* dummy entry exist -> wake up was delivered ahead of PF */
                hlist_del(&e->link);
                kfree(e);
                raw_spin_unlock(&b->lock);

                rcu_irq_exit();
                return;
        }

        n.token = token;
        n.cpu = smp_processor_id();
        n.halted = is_idle_task(current) ||
                   (IS_ENABLED(CONFIG_PREEMPT_COUNT)
                    ? preempt_count() > 1 || rcu_preempt_depth()
                    : interrupt_kernel);
        init_swait_queue_head(&n.wq);
        hlist_add_head(&n.link, &b->list);
        raw_spin_unlock(&b->lock);

        for (;;) {
                if (!n.halted)
                        prepare_to_swait(&n.wq, &wait, TASK_UNINTERRUPTIBLE);
                if (hlist_unhashed(&n.link))
                        break;

                rcu_irq_exit();

                if (!n.halted) {
                        local_irq_enable();
                        schedule();
                        local_irq_disable();
                } else {
                        /*
                         * We cannot reschedule. So halt.
                         */
                        native_safe_halt();
                        local_irq_disable();
                }

                rcu_irq_enter();
        }
        if (!n.halted)
                finish_swait(&n.wq, &wait);

        rcu_irq_exit();
        return;
}
EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait);

static void apf_task_wake_one(struct kvm_task_sleep_node *n)
{
        hlist_del_init(&n->link);
        if (n->halted)
                smp_send_reschedule(n->cpu);
        else if (swq_has_sleeper(&n->wq))
                swake_up(&n->wq);
}

static void apf_task_wake_all(void)
{
        int i;

        for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) {
                struct hlist_node *p, *next;
                struct kvm_task_sleep_head *b = &async_pf_sleepers[i];
                raw_spin_lock(&b->lock);
                hlist_for_each_safe(p, next, &b->list) {
                        struct kvm_task_sleep_node *n =
                                hlist_entry(p, typeof(*n), link);
                        if (n->cpu == smp_processor_id())
                                apf_task_wake_one(n);
                }
                raw_spin_unlock(&b->lock);
        }
}

void kvm_async_pf_task_wake(u32 token)
{
        u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
        struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
        struct kvm_task_sleep_node *n;

        if (token == ~0) {
                apf_task_wake_all();
                return;
        }

again:
        raw_spin_lock(&b->lock);
        n = _find_apf_task(b, token);
        if (!n) {
                /*
                 * async PF was not yet handled.
                 * Add dummy entry for the token.
                 */
                n = kzalloc(sizeof(*n), GFP_ATOMIC);
                if (!n) {
                        /*
                         * Allocation failed! Busy wait while other cpu
                         * handles async PF.
                         */
                        raw_spin_unlock(&b->lock);
                        cpu_relax();
                        goto again;
                }
                n->token = token;
                n->cpu = smp_processor_id();
                init_swait_queue_head(&n->wq);
                hlist_add_head(&n->link, &b->list);
        } else
                apf_task_wake_one(n);
        raw_spin_unlock(&b->lock);
        return;
}
EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake);

u32 kvm_read_and_reset_pf_reason(void)
{
        u32 reason = 0;

        if (__this_cpu_read(apf_reason.enabled)) {
                reason = __this_cpu_read(apf_reason.reason);
                __this_cpu_write(apf_reason.reason, 0);
        }

        return reason;
}
EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason);
NOKPROBE_SYMBOL(kvm_read_and_reset_pf_reason);

dotraplinkage void
do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
{
        enum ctx_state prev_state;

        switch (kvm_read_and_reset_pf_reason()) {
        default:
                do_page_fault(regs, error_code);
                break;
        case KVM_PV_REASON_PAGE_NOT_PRESENT:
                /* page is swapped out by the host. */
                prev_state = exception_enter();
                kvm_async_pf_task_wait((u32)read_cr2(), !user_mode(regs));
                exception_exit(prev_state);
                break;
        case KVM_PV_REASON_PAGE_READY:
                rcu_irq_enter();
                kvm_async_pf_task_wake((u32)read_cr2());
                rcu_irq_exit();
                break;
        }
}
NOKPROBE_SYMBOL(do_async_page_fault);

static void __init paravirt_ops_setup(void)
{
        pv_info.name = "KVM";

        if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
                pv_cpu_ops.io_delay = kvm_io_delay;

#ifdef CONFIG_X86_IO_APIC
        no_timer_check = 1;
#endif
}

static void kvm_register_steal_time(void)
{
        int cpu = smp_processor_id();
        struct kvm_steal_time *st = &per_cpu(steal_time, cpu);

        if (!has_steal_clock)
                return;

        wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED));
        pr_info("kvm-stealtime: cpu %d, msr %llx\n",
                cpu, (unsigned long long) slow_virt_to_phys(st));
}

static DEFINE_PER_CPU_DECRYPTED(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;

static notrace void kvm_guest_apic_eoi_write(u32 reg, u32 val)
{
        /**
         * This relies on __test_and_clear_bit to modify the memory
         * in a way that is atomic with respect to the local CPU.
         * The hypervisor only accesses this memory from the local CPU so
         * there's no need for lock or memory barriers.
         * An optimization barrier is implied in apic write.
         */
        if (__test_and_clear_bit(KVM_PV_EOI_BIT, this_cpu_ptr(&kvm_apic_eoi)))
                return;
        apic->native_eoi_write(APIC_EOI, APIC_EOI_ACK);
}

static void kvm_guest_cpu_init(void)
{
        if (!kvm_para_available())
                return;

        if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
                u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));

#ifdef CONFIG_PREEMPT
                pa |= KVM_ASYNC_PF_SEND_ALWAYS;
#endif
                pa |= KVM_ASYNC_PF_ENABLED;

                if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_VMEXIT))
                        pa |= KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT;

                wrmsrl(MSR_KVM_ASYNC_PF_EN, pa);
                __this_cpu_write(apf_reason.enabled, 1);
                printk(KERN_INFO"KVM setup async PF for cpu %d\n",
                       smp_processor_id());
        }

        if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) {
                unsigned long pa;
                /* Size alignment is implied but just to make it explicit. */
                BUILD_BUG_ON(__alignof__(kvm_apic_eoi) < 4);
                __this_cpu_write(kvm_apic_eoi, 0);
                pa = slow_virt_to_phys(this_cpu_ptr(&kvm_apic_eoi))
                        | KVM_MSR_ENABLED;
                wrmsrl(MSR_KVM_PV_EOI_EN, pa);
        }

        if (has_steal_clock)
                kvm_register_steal_time();
}

static void kvm_pv_disable_apf(void)
{
        if (!__this_cpu_read(apf_reason.enabled))
                return;

        wrmsrl(MSR_KVM_ASYNC_PF_EN, 0);
        __this_cpu_write(apf_reason.enabled, 0);

        printk(KERN_INFO"Unregister pv shared memory for cpu %d\n",
               smp_processor_id());
}

static void kvm_pv_guest_cpu_reboot(void *unused)
{
        /*
         * We disable PV EOI before we load a new kernel by kexec,
         * since MSR_KVM_PV_EOI_EN stores a pointer into old kernel's memory.
         * New kernel can re-enable when it boots.
         */
        if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
                wrmsrl(MSR_KVM_PV_EOI_EN, 0);
        kvm_pv_disable_apf();
        kvm_disable_steal_time();
}

static int kvm_pv_reboot_notify(struct notifier_block *nb,
                                unsigned long code, void *unused)
{
        if (code == SYS_RESTART)
                on_each_cpu(kvm_pv_guest_cpu_reboot, NULL, 1);
        return NOTIFY_DONE;
}

static struct notifier_block kvm_pv_reboot_nb = {
        .notifier_call = kvm_pv_reboot_notify,
};

static u64 kvm_steal_clock(int cpu)
{
        u64 steal;
        struct kvm_steal_time *src;
        int version;

        src = &per_cpu(steal_time, cpu);
        do {
                version = src->version;
                virt_rmb();
                steal = src->steal;
                virt_rmb();
        } while ((version & 1) || (version != src->version));

        return steal;
}

void kvm_disable_steal_time(void)
{
        if (!has_steal_clock)
                return;

        wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
}

static inline void __set_percpu_decrypted(void *ptr, unsigned long size)
{
        early_set_memory_decrypted((unsigned long) ptr, size);
}

/*
 * Iterate through all possible CPUs and map the memory region pointed
 * by apf_reason, steal_time and kvm_apic_eoi as decrypted at once.
 *
 * Note: we iterate through all possible CPUs to ensure that CPUs
 * hotplugged will have their per-cpu variable already mapped as
 * decrypted.
 */
static void __init sev_map_percpu_data(void)
{
        int cpu;

        if (!sev_active())
                return;

        for_each_possible_cpu(cpu) {
                __set_percpu_decrypted(&per_cpu(apf_reason, cpu), sizeof(apf_reason));
                __set_percpu_decrypted(&per_cpu(steal_time, cpu), sizeof(steal_time));
                __set_percpu_decrypted(&per_cpu(kvm_apic_eoi, cpu), sizeof(kvm_apic_eoi));
        }
}

#ifdef CONFIG_SMP
static void __init kvm_smp_prepare_cpus(unsigned int max_cpus)
{
        native_smp_prepare_cpus(max_cpus);
        if (kvm_para_has_hint(KVM_HINTS_REALTIME))
                static_branch_disable(&virt_spin_lock_key);
}

static void __init kvm_smp_prepare_boot_cpu(void)
{
        /*
         * Map the per-cpu variables as decrypted before kvm_guest_cpu_init()
         * shares the guest physical address with the hypervisor.
         */
        sev_map_percpu_data();

        kvm_guest_cpu_init();
        native_smp_prepare_boot_cpu();
        kvm_spinlock_init();
}

static void kvm_guest_cpu_offline(void)
{
        kvm_disable_steal_time();
        if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
                wrmsrl(MSR_KVM_PV_EOI_EN, 0);
        kvm_pv_disable_apf();
        apf_task_wake_all();
}

static int kvm_cpu_online(unsigned int cpu)
{
        local_irq_disable();
        kvm_guest_cpu_init();
        local_irq_enable();
        return 0;
}

static int kvm_cpu_down_prepare(unsigned int cpu)
{
        local_irq_disable();
        kvm_guest_cpu_offline();
        local_irq_enable();
        return 0;
}
#endif

static void __init kvm_apf_trap_init(void)
{
        update_intr_gate(X86_TRAP_PF, async_page_fault);
}

static DEFINE_PER_CPU(cpumask_var_t, __pv_tlb_mask);

static void kvm_flush_tlb_others(const struct cpumask *cpumask,
                        const struct flush_tlb_info *info)
{
        u8 state;
        int cpu;
        struct kvm_steal_time *src;
        struct cpumask *flushmask = this_cpu_cpumask_var_ptr(__pv_tlb_mask);

        cpumask_copy(flushmask, cpumask);
        /*
         * We have to call flush only on online vCPUs. And
         * queue flush_on_enter for pre-empted vCPUs
         */
        for_each_cpu(cpu, flushmask) {
                src = &per_cpu(steal_time, cpu);
                state = READ_ONCE(src->preempted);
                if ((state & KVM_VCPU_PREEMPTED)) {
                        if (try_cmpxchg(&src->preempted, &state,
                                        state | KVM_VCPU_FLUSH_TLB))
                                __cpumask_clear_cpu(cpu, flushmask);
                }
        }

        native_flush_tlb_others(flushmask, info);
}

static void __init kvm_guest_init(void)
{
        int i;

        if (!kvm_para_available())
                return;

        paravirt_ops_setup();
        register_reboot_notifier(&kvm_pv_reboot_nb);
        for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
                raw_spin_lock_init(&async_pf_sleepers[i].lock);
        if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
                x86_init.irqs.trap_init = kvm_apf_trap_init;

        if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
                has_steal_clock = 1;
                pv_time_ops.steal_clock = kvm_steal_clock;
        }

        if (kvm_para_has_feature(KVM_FEATURE_PV_TLB_FLUSH) &&
            !kvm_para_has_hint(KVM_HINTS_REALTIME) &&
            kvm_para_has_feature(KVM_FEATURE_STEAL_TIME))
                pv_mmu_ops.flush_tlb_others = kvm_flush_tlb_others;

        if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
                apic_set_eoi_write(kvm_guest_apic_eoi_write);

        if (kvmclock_vsyscall)
                kvm_setup_vsyscall_timeinfo();

#ifdef CONFIG_SMP
        smp_ops.smp_prepare_cpus = kvm_smp_prepare_cpus;
        smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
        if (cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "x86/kvm:online",
                                      kvm_cpu_online, kvm_cpu_down_prepare) < 0)
                pr_err("kvm_guest: Failed to install cpu hotplug callbacks\n");
#else
        sev_map_percpu_data();
        kvm_guest_cpu_init();
#endif

        /*
         * Hard lockup detection is enabled by default. Disable it, as guests
         * can get false positives too easily, for example if the host is
         * overcommitted.
         */
        hardlockup_detector_disable();
}

static noinline uint32_t __kvm_cpuid_base(void)
{
        if (boot_cpu_data.cpuid_level < 0)
                return 0;       /* So we don't blow up on old processors */

        if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
                return hypervisor_cpuid_base("KVMKVMKVM\0\0\0", 0);

        return 0;
}

static inline uint32_t kvm_cpuid_base(void)
{
        static int kvm_cpuid_base = -1;

        if (kvm_cpuid_base == -1)
                kvm_cpuid_base = __kvm_cpuid_base();

        return kvm_cpuid_base;
}

bool kvm_para_available(void)
{
        return kvm_cpuid_base() != 0;
}
EXPORT_SYMBOL_GPL(kvm_para_available);

unsigned int kvm_arch_para_features(void)
{
        return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES);
}

unsigned int kvm_arch_para_hints(void)
{
        return cpuid_edx(kvm_cpuid_base() | KVM_CPUID_FEATURES);
}

static uint32_t __init kvm_detect(void)
{
        return kvm_cpuid_base();
}

const __initconst struct hypervisor_x86 x86_hyper_kvm = {
        .name                   = "KVM",
        .detect                 = kvm_detect,
        .type                   = X86_HYPER_KVM,
        .init.guest_late_init   = kvm_guest_init,
        .init.x2apic_available  = kvm_para_available,
};

static __init int activate_jump_labels(void)
{
        if (has_steal_clock) {
                static_key_slow_inc(&paravirt_steal_enabled);
                if (steal_acc)
                        static_key_slow_inc(&paravirt_steal_rq_enabled);
        }

        return 0;
}
arch_initcall(activate_jump_labels);

static __init int kvm_setup_pv_tlb_flush(void)
{
        int cpu;

        if (kvm_para_has_feature(KVM_FEATURE_PV_TLB_FLUSH) &&
            !kvm_para_has_hint(KVM_HINTS_REALTIME) &&
            kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
                for_each_possible_cpu(cpu) {
                        zalloc_cpumask_var_node(per_cpu_ptr(&__pv_tlb_mask, cpu),
                                GFP_KERNEL, cpu_to_node(cpu));
                }
                pr_info("KVM setup pv remote TLB flush\n");
        }

        return 0;
}
arch_initcall(kvm_setup_pv_tlb_flush);

#ifdef CONFIG_PARAVIRT_SPINLOCKS

/* Kick a cpu by its apicid. Used to wake up a halted vcpu */
static void kvm_kick_cpu(int cpu)
{
        int apicid;
        unsigned long flags = 0;

        apicid = per_cpu(x86_cpu_to_apicid, cpu);
        kvm_hypercall2(KVM_HC_KICK_CPU, flags, apicid);
}

#include <asm/qspinlock.h>

static void kvm_wait(u8 *ptr, u8 val)
{
        unsigned long flags;

        if (in_nmi())
                return;

        local_irq_save(flags);

        if (READ_ONCE(*ptr) != val)
                goto out;

        /*
         * halt until it's our turn and kicked. Note that we do safe halt
         * for irq enabled case to avoid hang when lock info is overwritten
         * in irq spinlock slowpath and no spurious interrupt occur to save us.
         */
        if (arch_irqs_disabled_flags(flags))
                halt();
        else
                safe_halt();

out:
        local_irq_restore(flags);
}

#ifdef CONFIG_X86_32
__visible bool __kvm_vcpu_is_preempted(long cpu)
{
        struct kvm_steal_time *src = &per_cpu(steal_time, cpu);

        return !!(src->preempted & KVM_VCPU_PREEMPTED);
}
PV_CALLEE_SAVE_REGS_THUNK(__kvm_vcpu_is_preempted);

#else

#include <asm/asm-offsets.h>

extern bool __raw_callee_save___kvm_vcpu_is_preempted(long);

/*
 * Hand-optimize version for x86-64 to avoid 8 64-bit register saving and
 * restoring to/from the stack.
 */
asm(
".pushsection .text;"
".global __raw_callee_save___kvm_vcpu_is_preempted;"
".type __raw_callee_save___kvm_vcpu_is_preempted, @function;"
"__raw_callee_save___kvm_vcpu_is_preempted:"
"movq   __per_cpu_offset(,%rdi,8), %rax;"
"cmpb   $0, " __stringify(KVM_STEAL_TIME_preempted) "+steal_time(%rax);"
"setne  %al;"
"ret;"
".popsection");

#endif

/*
 * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present.
 */
void __init kvm_spinlock_init(void)
{
        if (!kvm_para_available())
                return;
        /* Does host kernel support KVM_FEATURE_PV_UNHALT? */
        if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
                return;

        if (kvm_para_has_hint(KVM_HINTS_REALTIME))
                return;

        __pv_init_lock_hash();
        pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
        pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
        pv_lock_ops.wait = kvm_wait;
        pv_lock_ops.kick = kvm_kick_cpu;

        if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
                pv_lock_ops.vcpu_is_preempted =
                        PV_CALLEE_SAVE(__kvm_vcpu_is_preempted);
        }
}

#endif  /* CONFIG_PARAVIRT_SPINLOCKS */