#include <linux/init.h>

#include <linux/mm.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/cpu.h>

#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
#include <asm/cache.h>
#include <asm/apic.h>
#include <asm/uv/uv.h>
#include <linux/debugfs.h>

DEFINE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate)
                        = { &init_mm, 0, };

/*
 *      Smarter SMP flushing macros.
 *              c/o Linus Torvalds.
 *
 *      These mean you can really definitely utterly forget about
 *      writing to user space from interrupts. (Its not allowed anyway).
 *
 *      Optimizations Manfred Spraul <manfred@colorfullife.com>
 *
 *      More scalable flush, from Andi Kleen
 *
 *      Implement flush IPI by CALL_FUNCTION_VECTOR, Alex Shi
 */

struct flush_tlb_info {
        struct mm_struct *flush_mm;
        unsigned long flush_start;
        unsigned long flush_end;
};

/*
 * We cannot call mmdrop() because we are in interrupt context,
 * instead update mm->cpu_vm_mask.
 */
void leave_mm(int cpu)
{
        struct mm_struct *active_mm = this_cpu_read(cpu_tlbstate.active_mm);
        if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
                BUG();
        if (cpumask_test_cpu(cpu, mm_cpumask(active_mm))) {
                cpumask_clear_cpu(cpu, mm_cpumask(active_mm));
                load_cr3(swapper_pg_dir);
        }
}
EXPORT_SYMBOL_GPL(leave_mm);

/*
 * The flush IPI assumes that a thread switch happens in this order:
 * [cpu0: the cpu that switches]
 * 1) switch_mm() either 1a) or 1b)
 * 1a) thread switch to a different mm
 * 1a1) set cpu_tlbstate to TLBSTATE_OK
 *      Now the tlb flush NMI handler flush_tlb_func won't call leave_mm
 *      if cpu0 was in lazy tlb mode.
 * 1a2) update cpu active_mm
 *      Now cpu0 accepts tlb flushes for the new mm.
 * 1a3) cpu_set(cpu, new_mm->cpu_vm_mask);
 *      Now the other cpus will send tlb flush ipis.
 * 1a4) change cr3.
 * 1a5) cpu_clear(cpu, old_mm->cpu_vm_mask);
 *      Stop ipi delivery for the old mm. This is not synchronized with
 *      the other cpus, but flush_tlb_func ignore flush ipis for the wrong
 *      mm, and in the worst case we perform a superfluous tlb flush.
 * 1b) thread switch without mm change
 *      cpu active_mm is correct, cpu0 already handles flush ipis.
 * 1b1) set cpu_tlbstate to TLBSTATE_OK
 * 1b2) test_and_set the cpu bit in cpu_vm_mask.
 *      Atomically set the bit [other cpus will start sending flush ipis],
 *      and test the bit.
 * 1b3) if the bit was 0: leave_mm was called, flush the tlb.
 * 2) switch %%esp, ie current
 *
 * The interrupt must handle 2 special cases:
 * - cr3 is changed before %%esp, ie. it cannot use current->{active_,}mm.
 * - the cpu performs speculative tlb reads, i.e. even if the cpu only
 *   runs in kernel space, the cpu could load tlb entries for user space
 *   pages.
 *
 * The good news is that cpu_tlbstate is local to each cpu, no
 * write/read ordering problems.
 */

/*
 * TLB flush funcation:
 * 1) Flush the tlb entries if the cpu uses the mm that's being flushed.
 * 2) Leave the mm if we are in the lazy tlb mode.
 */
static void flush_tlb_func(void *info)
{
        struct flush_tlb_info *f = info;

        inc_irq_stat(irq_tlb_count);

        if (f->flush_mm != this_cpu_read(cpu_tlbstate.active_mm))
                return;

        if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK) {
                if (f->flush_end == TLB_FLUSH_ALL)
                        local_flush_tlb();
                else if (!f->flush_end)
                        __flush_tlb_single(f->flush_start);
                else {
                        unsigned long addr;
                        addr = f->flush_start;
                        while (addr < f->flush_end) {
                                __flush_tlb_single(addr);
                                addr += PAGE_SIZE;
                        }
                }
        } else
                leave_mm(smp_processor_id());

}

void native_flush_tlb_others(const struct cpumask *cpumask,
                                 struct mm_struct *mm, unsigned long start,
                                 unsigned long end)
{
        struct flush_tlb_info info;
        info.flush_mm = mm;
        info.flush_start = start;
        info.flush_end = end;

        if (is_uv_system()) {
                unsigned int cpu;

                cpu = smp_processor_id();
                cpumask = uv_flush_tlb_others(cpumask, mm, start, end, cpu);
                if (cpumask)
                        smp_call_function_many(cpumask, flush_tlb_func,
                                                                &info, 1);
                return;
        }
        smp_call_function_many(cpumask, flush_tlb_func, &info, 1);
}

void flush_tlb_current_task(void)
{
        struct mm_struct *mm = current->mm;

        preempt_disable();

        local_flush_tlb();
        if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
                flush_tlb_others(mm_cpumask(mm), mm, 0UL, TLB_FLUSH_ALL);
        preempt_enable();
}

/*
 * It can find out the THP large page, or
 * HUGETLB page in tlb_flush when THP disabled
 */
static inline unsigned long has_large_page(struct mm_struct *mm,
                                 unsigned long start, unsigned long end)
{
        pgd_t *pgd;
        pud_t *pud;
        pmd_t *pmd;
        unsigned long addr = ALIGN(start, HPAGE_SIZE);
        for (; addr < end; addr += HPAGE_SIZE) {
                pgd = pgd_offset(mm, addr);
                if (likely(!pgd_none(*pgd))) {
                        pud = pud_offset(pgd, addr);
                        if (likely(!pud_none(*pud))) {
                                pmd = pmd_offset(pud, addr);
                                if (likely(!pmd_none(*pmd)))
                                        if (pmd_large(*pmd))
                                                return addr;
                        }
                }
        }
        return 0;
}

void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
                                unsigned long end, unsigned long vmflag)
{
        unsigned long addr;
        unsigned act_entries, tlb_entries = 0;

        preempt_disable();
        if (current->active_mm != mm)
                goto flush_all;

        if (!current->mm) {
                leave_mm(smp_processor_id());
                goto flush_all;
        }

        if (end == TLB_FLUSH_ALL || tlb_flushall_shift == -1
                                        || vmflag & VM_HUGETLB) {
                local_flush_tlb();
                goto flush_all;
        }

        /* In modern CPU, last level tlb used for both data/ins */
        if (vmflag & VM_EXEC)
                tlb_entries = tlb_lli_4k[ENTRIES];
        else
                tlb_entries = tlb_lld_4k[ENTRIES];
        /* Assume all of TLB entries was occupied by this task */
        act_entries = mm->total_vm > tlb_entries ? tlb_entries : mm->total_vm;

        /* tlb_flushall_shift is on balance point, details in commit log */
        if ((end - start) >> PAGE_SHIFT > act_entries >> tlb_flushall_shift)
                local_flush_tlb();
        else {
                if (has_large_page(mm, start, end)) {
                        local_flush_tlb();
                        goto flush_all;
                }
                /* flush range by one by one 'invlpg' */
                for (addr = start; addr < end;  addr += PAGE_SIZE)
                        __flush_tlb_single(addr);

                if (cpumask_any_but(mm_cpumask(mm),
                                smp_processor_id()) < nr_cpu_ids)
                        flush_tlb_others(mm_cpumask(mm), mm, start, end);
                preempt_enable();
                return;
        }

flush_all:
        if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
                flush_tlb_others(mm_cpumask(mm), mm, 0UL, TLB_FLUSH_ALL);
        preempt_enable();
}

void flush_tlb_page(struct vm_area_struct *vma, unsigned long start)
{
        struct mm_struct *mm = vma->vm_mm;

        preempt_disable();

        if (current->active_mm == mm) {
                if (current->mm)
                        __flush_tlb_one(start);
                else
                        leave_mm(smp_processor_id());
        }

        if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
                flush_tlb_others(mm_cpumask(mm), mm, start, 0UL);

        preempt_enable();
}

static void do_flush_tlb_all(void *info)
{
        __flush_tlb_all();
        if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_LAZY)
                leave_mm(smp_processor_id());
}

void flush_tlb_all(void)
{
        on_each_cpu(do_flush_tlb_all, NULL, 1);
}

static void do_kernel_range_flush(void *info)
{
        struct flush_tlb_info *f = info;
        unsigned long addr;

        /* flush range by one by one 'invlpg' */
        for (addr = f->flush_start; addr < f->flush_end; addr += PAGE_SIZE)
                __flush_tlb_single(addr);
}

void flush_tlb_kernel_range(unsigned long start, unsigned long end)
{
        unsigned act_entries;
        struct flush_tlb_info info;

        /* In modern CPU, last level tlb used for both data/ins */
        act_entries = tlb_lld_4k[ENTRIES];

        /* Balance as user space task's flush, a bit conservative */
        if (end == TLB_FLUSH_ALL || tlb_flushall_shift == -1 ||
                (end - start) >> PAGE_SHIFT > act_entries >> tlb_flushall_shift)

                on_each_cpu(do_flush_tlb_all, NULL, 1);
        else {
                info.flush_start = start;
                info.flush_end = end;
                on_each_cpu(do_kernel_range_flush, &info, 1);
        }
}

#ifdef CONFIG_DEBUG_TLBFLUSH
static ssize_t tlbflush_read_file(struct file *file, char __user *user_buf,
                             size_t count, loff_t *ppos)
{
        char buf[32];
        unsigned int len;

        len = sprintf(buf, "%hd\n", tlb_flushall_shift);
        return simple_read_from_buffer(user_buf, count, ppos, buf, len);
}

static ssize_t tlbflush_write_file(struct file *file,
                 const char __user *user_buf, size_t count, loff_t *ppos)
{
        char buf[32];
        ssize_t len;
        s8 shift;

        len = min(count, sizeof(buf) - 1);
        if (copy_from_user(buf, user_buf, len))
                return -EFAULT;

        buf[len] = '\0';
        if (kstrtos8(buf, 0, &shift))
                return -EINVAL;

        if (shift < -1 || shift >= BITS_PER_LONG)
                return -EINVAL;

        tlb_flushall_shift = shift;
        return count;
}

static const struct file_operations fops_tlbflush = {
        .read = tlbflush_read_file,
        .write = tlbflush_write_file,
        .llseek = default_llseek,
};

static int __init create_tlb_flushall_shift(void)
{
        debugfs_create_file("tlb_flushall_shift", S_IRUSR | S_IWUSR,
                            arch_debugfs_dir, NULL, &fops_tlbflush);
        return 0;
}
late_initcall(create_tlb_flushall_shift);
#endif