#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>

/*
 *      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);
                /*
                 * This gets called in the idle path where RCU
                 * functions differently.  Tracing normally
                 * uses RCU, so we have to call the tracepoint
                 * specially here.
                 */
                trace_tlb_flush_rcuidle(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
        }
}
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 (!f->flush_end)
                f->flush_end = f->flush_start + PAGE_SIZE;

        count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
        if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK) {
                if (f->flush_end == TLB_FLUSH_ALL) {
                        local_flush_tlb();
                        trace_tlb_flush(TLB_REMOTE_SHOOTDOWN, TLB_FLUSH_ALL);
                } else {
                        unsigned long addr;
                        unsigned long nr_pages =
                                (f->flush_end - f->flush_start) / PAGE_SIZE;
                        addr = f->flush_start;
                        while (addr < f->flush_end) {
                                __flush_tlb_single(addr);
                                addr += PAGE_SIZE;
                        }
                        trace_tlb_flush(TLB_REMOTE_SHOOTDOWN, nr_pages);
                }
        } 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;

        count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
        trace_tlb_flush(TLB_REMOTE_SEND_IPI, end - start);
        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();

        count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
        local_flush_tlb();
        trace_tlb_flush(TLB_LOCAL_SHOOTDOWN, TLB_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();
}

/*
 * See Documentation/x86/tlb.txt for details.  We choose 33
 * because it is large enough to cover the vast majority (at
 * least 95%) of allocations, and is small enough that we are
 * confident it will not cause too much overhead.  Each single
 * flush is about 100 ns, so this caps the maximum overhead at
 * _about_ 3,000 ns.
 *
 * This is in units of pages.
 */
static unsigned long tlb_single_page_flush_ceiling __read_mostly = 33;

void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
                                unsigned long end, unsigned long vmflag)
{
        unsigned long addr;
        /* do a global flush by default */
        unsigned long base_pages_to_flush = TLB_FLUSH_ALL;

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

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

        if ((end != TLB_FLUSH_ALL) && !(vmflag & VM_HUGETLB))
                base_pages_to_flush = (end - start) >> PAGE_SHIFT;

        if (base_pages_to_flush > tlb_single_page_flush_ceiling) {
                base_pages_to_flush = TLB_FLUSH_ALL;
                count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
                local_flush_tlb();
        } else {
                /* flush range by one by one 'invlpg' */
                for (addr = start; addr < end;  addr += PAGE_SIZE) {
                        count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ONE);
                        __flush_tlb_single(addr);
                }
        }
        trace_tlb_flush(TLB_LOCAL_MM_SHOOTDOWN, base_pages_to_flush);
out:
        if (base_pages_to_flush == TLB_FLUSH_ALL) {
                start = 0UL;
                end = TLB_FLUSH_ALL;
        }
        if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
                flush_tlb_others(mm_cpumask(mm), mm, start, end);
        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)
{
        count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
        __flush_tlb_all();
        if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_LAZY)
                leave_mm(smp_processor_id());
}

void flush_tlb_all(void)
{
        count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
        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)
{

        /* Balance as user space task's flush, a bit conservative */
        if (end == TLB_FLUSH_ALL ||
            (end - start) > tlb_single_page_flush_ceiling * PAGE_SIZE) {
                on_each_cpu(do_flush_tlb_all, NULL, 1);
        } else {
                struct flush_tlb_info info;
                info.flush_start = start;
                info.flush_end = end;
                on_each_cpu(do_kernel_range_flush, &info, 1);
        }
}

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, "%ld\n", tlb_single_page_flush_ceiling);
        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;
        int ceiling;

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

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

        if (ceiling < 0)
                return -EINVAL;

        tlb_single_page_flush_ceiling = ceiling;
        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_single_page_flush_ceiling(void)
{
        debugfs_create_file("tlb_single_page_flush_ceiling", S_IRUSR | S_IWUSR,
                            arch_debugfs_dir, NULL, &fops_tlbflush);
        return 0;
}
late_initcall(create_tlb_single_page_flush_ceiling);