#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 <asm/tlbflush.h>
#include <asm/mmu_context.h>
#include <asm/cache.h>
#include <asm/apic.h>
#include <asm/uv/uv.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
 *
 *      To avoid global state use 8 different call vectors.
 *      Each CPU uses a specific vector to trigger flushes on other
 *      CPUs. Depending on the received vector the target CPUs look into
 *      the right array slot for the flush data.
 *
 *      With more than 8 CPUs they are hashed to the 8 available
 *      vectors. The limited global vector space forces us to this right now.
 *      In future when interrupts are split into per CPU domains this could be
 *      fixed, at the cost of triggering multiple IPIs in some cases.
 */

union smp_flush_state {
        struct {
                struct mm_struct *flush_mm;
                unsigned long flush_va;
                raw_spinlock_t tlbstate_lock;
                DECLARE_BITMAP(flush_cpumask, NR_CPUS);
        };
        char pad[INTERNODE_CACHE_BYTES];
} ____cacheline_internodealigned_in_smp;

/* State is put into the per CPU data section, but padded
   to a full cache line because other CPUs can access it and we don't
   want false sharing in the per cpu data segment. */
static union smp_flush_state flush_state[NUM_INVALIDATE_TLB_VECTORS];

/*
 * We cannot call mmdrop() because we are in interrupt context,
 * instead update mm->cpu_vm_mask.
 */
void leave_mm(int cpu)
{
        if (percpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
                BUG();
        cpumask_clear_cpu(cpu,
                          mm_cpumask(percpu_read(cpu_tlbstate.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) cpu_clear(cpu, old_mm->cpu_vm_mask);
 *      Stop ipi delivery for the old mm. This is not synchronized with
 *      the other cpus, but smp_invalidate_interrupt ignore flush ipis
 *      for the wrong mm, and in the worst case we perform a superfluous
 *      tlb flush.
 * 1a2) set cpu mmu_state to TLBSTATE_OK
 *      Now the smp_invalidate_interrupt won't call leave_mm if cpu0
 *      was in lazy tlb mode.
 * 1a3) update cpu active_mm
 *      Now cpu0 accepts tlb flushes for the new mm.
 * 1a4) cpu_set(cpu, new_mm->cpu_vm_mask);
 *      Now the other cpus will send tlb flush ipis.
 * 1a4) change cr3.
 * 1b) thread switch without mm change
 *      cpu active_mm is correct, cpu0 already handles
 *      flush ipis.
 * 1b1) set cpu mmu_state 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 mmu_state is local to each cpu, no
 * write/read ordering problems.
 */

/*
 * TLB flush IPI:
 *
 * 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.
 *
 * Interrupts are disabled.
 */

/*
 * FIXME: use of asmlinkage is not consistent.  On x86_64 it's noop
 * but still used for documentation purpose but the usage is slightly
 * inconsistent.  On x86_32, asmlinkage is regparm(0) but interrupt
 * entry calls in with the first parameter in %eax.  Maybe define
 * intrlinkage?
 */
#ifdef CONFIG_X86_64
asmlinkage
#endif
void smp_invalidate_interrupt(struct pt_regs *regs)
{
        unsigned int cpu;
        unsigned int sender;
        union smp_flush_state *f;

        cpu = smp_processor_id();
        /*
         * orig_rax contains the negated interrupt vector.
         * Use that to determine where the sender put the data.
         */
        sender = ~regs->orig_ax - INVALIDATE_TLB_VECTOR_START;
        f = &flush_state[sender];

        if (!cpumask_test_cpu(cpu, to_cpumask(f->flush_cpumask)))
                goto out;
                /*
                 * This was a BUG() but until someone can quote me the
                 * line from the intel manual that guarantees an IPI to
                 * multiple CPUs is retried _only_ on the erroring CPUs
                 * its staying as a return
                 *
                 * BUG();
                 */

        if (f->flush_mm == percpu_read(cpu_tlbstate.active_mm)) {
                if (percpu_read(cpu_tlbstate.state) == TLBSTATE_OK) {
                        if (f->flush_va == TLB_FLUSH_ALL)
                                local_flush_tlb();
                        else
                                __flush_tlb_one(f->flush_va);
                } else
                        leave_mm(cpu);
        }
out:
        ack_APIC_irq();
        smp_mb__before_clear_bit();
        cpumask_clear_cpu(cpu, to_cpumask(f->flush_cpumask));
        smp_mb__after_clear_bit();
        inc_irq_stat(irq_tlb_count);
}

static void flush_tlb_others_ipi(const struct cpumask *cpumask,
                                 struct mm_struct *mm, unsigned long va)
{
        unsigned int sender;
        union smp_flush_state *f;

        /* Caller has disabled preemption */
        sender = smp_processor_id() % NUM_INVALIDATE_TLB_VECTORS;
        f = &flush_state[sender];

        /*
         * Could avoid this lock when
         * num_online_cpus() <= NUM_INVALIDATE_TLB_VECTORS, but it is
         * probably not worth checking this for a cache-hot lock.
         */
        raw_spin_lock(&f->tlbstate_lock);

        f->flush_mm = mm;
        f->flush_va = va;
        if (cpumask_andnot(to_cpumask(f->flush_cpumask), cpumask, cpumask_of(smp_processor_id()))) {
                /*
                 * We have to send the IPI only to
                 * CPUs affected.
                 */
                apic->send_IPI_mask(to_cpumask(f->flush_cpumask),
                              INVALIDATE_TLB_VECTOR_START + sender);

                while (!cpumask_empty(to_cpumask(f->flush_cpumask)))
                        cpu_relax();
        }

        f->flush_mm = NULL;
        f->flush_va = 0;
        raw_spin_unlock(&f->tlbstate_lock);
}

void native_flush_tlb_others(const struct cpumask *cpumask,
                             struct mm_struct *mm, unsigned long va)
{
        if (is_uv_system()) {
                unsigned int cpu;

                cpu = get_cpu();
                cpumask = uv_flush_tlb_others(cpumask, mm, va, cpu);
                if (cpumask)
                        flush_tlb_others_ipi(cpumask, mm, va);
                put_cpu();
                return;
        }
        flush_tlb_others_ipi(cpumask, mm, va);
}

static int __cpuinit init_smp_flush(void)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(flush_state); i++)
                raw_spin_lock_init(&flush_state[i].tlbstate_lock);

        return 0;
}
core_initcall(init_smp_flush);

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, TLB_FLUSH_ALL);
        preempt_enable();
}

void flush_tlb_mm(struct mm_struct *mm)
{
        preempt_disable();

        if (current->active_mm == mm) {
                if (current->mm)
                        local_flush_tlb();
                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, TLB_FLUSH_ALL);

        preempt_enable();
}

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

        preempt_disable();

        if (current->active_mm == mm) {
                if (current->mm)
                        __flush_tlb_one(va);
                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, va);

        preempt_enable();
}

static void do_flush_tlb_all(void *info)
{
        unsigned long cpu = smp_processor_id();

        __flush_tlb_all();
        if (percpu_read(cpu_tlbstate.state) == TLBSTATE_LAZY)
                leave_mm(cpu);
}

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