x86/mm: Pass flush_tlb_info to flush_tlb_others() etc

[mirror_ubuntu-artful-kernel.git] / arch / x86 / mm / tlb.c

#include <linux/init.h>

#include <linux/mm.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/export.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
 */

#ifdef CONFIG_SMP

/*
 * 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);

#endif /* CONFIG_SMP */

void switch_mm(struct mm_struct *prev, struct mm_struct *next,
               struct task_struct *tsk)
{
        unsigned long flags;

        local_irq_save(flags);
        switch_mm_irqs_off(prev, next, tsk);
        local_irq_restore(flags);
}

void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
                        struct task_struct *tsk)
{
        unsigned cpu = smp_processor_id();

        if (likely(prev != next)) {
                if (IS_ENABLED(CONFIG_VMAP_STACK)) {
                        /*
                         * If our current stack is in vmalloc space and isn't
                         * mapped in the new pgd, we'll double-fault.  Forcibly
                         * map it.
                         */
                        unsigned int stack_pgd_index = pgd_index(current_stack_pointer());

                        pgd_t *pgd = next->pgd + stack_pgd_index;

                        if (unlikely(pgd_none(*pgd)))
                                set_pgd(pgd, init_mm.pgd[stack_pgd_index]);
                }

#ifdef CONFIG_SMP
                this_cpu_write(cpu_tlbstate.state, TLBSTATE_OK);
                this_cpu_write(cpu_tlbstate.active_mm, next);
#endif

                cpumask_set_cpu(cpu, mm_cpumask(next));

                /*
                 * Re-load page tables.
                 *
                 * This logic has an ordering constraint:
                 *
                 *  CPU 0: Write to a PTE for 'next'
                 *  CPU 0: load bit 1 in mm_cpumask.  if nonzero, send IPI.
                 *  CPU 1: set bit 1 in next's mm_cpumask
                 *  CPU 1: load from the PTE that CPU 0 writes (implicit)
                 *
                 * We need to prevent an outcome in which CPU 1 observes
                 * the new PTE value and CPU 0 observes bit 1 clear in
                 * mm_cpumask.  (If that occurs, then the IPI will never
                 * be sent, and CPU 0's TLB will contain a stale entry.)
                 *
                 * The bad outcome can occur if either CPU's load is
                 * reordered before that CPU's store, so both CPUs must
                 * execute full barriers to prevent this from happening.
                 *
                 * Thus, switch_mm needs a full barrier between the
                 * store to mm_cpumask and any operation that could load
                 * from next->pgd.  TLB fills are special and can happen
                 * due to instruction fetches or for no reason at all,
                 * and neither LOCK nor MFENCE orders them.
                 * Fortunately, load_cr3() is serializing and gives the
                 * ordering guarantee we need.
                 *
                 */
                load_cr3(next->pgd);

                trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);

                /* Stop flush ipis for the previous mm */
                cpumask_clear_cpu(cpu, mm_cpumask(prev));

                /* Load per-mm CR4 state */
                load_mm_cr4(next);

#ifdef CONFIG_MODIFY_LDT_SYSCALL
                /*
                 * Load the LDT, if the LDT is different.
                 *
                 * It's possible that prev->context.ldt doesn't match
                 * the LDT register.  This can happen if leave_mm(prev)
                 * was called and then modify_ldt changed
                 * prev->context.ldt but suppressed an IPI to this CPU.
                 * In this case, prev->context.ldt != NULL, because we
                 * never set context.ldt to NULL while the mm still
                 * exists.  That means that next->context.ldt !=
                 * prev->context.ldt, because mms never share an LDT.
                 */
                if (unlikely(prev->context.ldt != next->context.ldt))
                        load_mm_ldt(next);
#endif
        }
#ifdef CONFIG_SMP
          else {
                this_cpu_write(cpu_tlbstate.state, TLBSTATE_OK);
                BUG_ON(this_cpu_read(cpu_tlbstate.active_mm) != next);

                if (!cpumask_test_cpu(cpu, mm_cpumask(next))) {
                        /*
                         * On established mms, the mm_cpumask is only changed
                         * from irq context, from ptep_clear_flush() while in
                         * lazy tlb mode, and here. Irqs are blocked during
                         * schedule, protecting us from simultaneous changes.
                         */
                        cpumask_set_cpu(cpu, mm_cpumask(next));

                        /*
                         * We were in lazy tlb mode and leave_mm disabled
                         * tlb flush IPI delivery. We must reload CR3
                         * to make sure to use no freed page tables.
                         *
                         * As above, load_cr3() is serializing and orders TLB
                         * fills with respect to the mm_cpumask write.
                         */
                        load_cr3(next->pgd);
                        trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
                        load_mm_cr4(next);
                        load_mm_ldt(next);
                }
        }
#endif
}

#ifdef CONFIG_SMP

/*
 * 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)
{
        const struct flush_tlb_info *f = info;

        inc_irq_stat(irq_tlb_count);

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

        count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);

        if (this_cpu_read(cpu_tlbstate.state) != TLBSTATE_OK) {
                leave_mm(smp_processor_id());
                return;
        }

        if (f->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->end - f->start) / PAGE_SIZE;
                addr = f->start;
                while (addr < f->end) {
                        __flush_tlb_single(addr);
                        addr += PAGE_SIZE;
                }
                trace_tlb_flush(TLB_REMOTE_SHOOTDOWN, nr_pages);
        }
}

void native_flush_tlb_others(const struct cpumask *cpumask,
                             const struct flush_tlb_info *info)
{
        count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
        if (info->end == TLB_FLUSH_ALL)
                trace_tlb_flush(TLB_REMOTE_SEND_IPI, TLB_FLUSH_ALL);
        else
                trace_tlb_flush(TLB_REMOTE_SEND_IPI,
                                (info->end - info->start) >> PAGE_SHIFT);

        if (is_uv_system()) {
                unsigned int cpu;

                cpu = smp_processor_id();
                cpumask = uv_flush_tlb_others(cpumask, info);
                if (cpumask)
                        smp_call_function_many(cpumask, flush_tlb_func,
                                               (void *)info, 1);
                return;
        }
        smp_call_function_many(cpumask, flush_tlb_func,
                               (void *)info, 1);
}

/*
 * 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;
        struct flush_tlb_info info;
        /* do a global flush by default */
        unsigned long base_pages_to_flush = TLB_FLUSH_ALL;

        preempt_disable();

        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;

        if (current->active_mm != mm) {
                /* Synchronize with switch_mm. */
                smp_mb();

                goto out;
        }

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

                /* Synchronize with switch_mm. */
                smp_mb();

                goto out;
        }

        /*
         * Both branches below are implicit full barriers (MOV to CR or
         * INVLPG) that synchronize with switch_mm.
         */
        if (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:
        info.mm = mm;
        if (base_pages_to_flush == TLB_FLUSH_ALL) {
                info.start = 0UL;
                info.end = TLB_FLUSH_ALL;
        } else {
                info.start = start;
                info.end = end;
        }
        if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
                flush_tlb_others(mm_cpumask(mm), &info);
        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->start; addr < f->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.start = start;
                info.end = end;
                on_each_cpu(do_kernel_range_flush, &info, 1);
        }
}

void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch)
{
        struct flush_tlb_info info = {
                .mm = NULL,
                .start = 0UL,
                .end = TLB_FLUSH_ALL,
        };

        int cpu = get_cpu();

        if (cpumask_test_cpu(cpu, &batch->cpumask)) {
                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(&batch->cpumask, cpu) < nr_cpu_ids)
                flush_tlb_others(&batch->cpumask, &info);
        cpumask_clear(&batch->cpumask);

        put_cpu();
}

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);

#endif /* CONFIG_SMP */