Release 4.10 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


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);
	}
}
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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);
}

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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
}

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#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)
{
	struct flush_tlb_info *f = info;

	inc_irq_stat(irq_tlb_count);

	if (f->flush_mm && f->flush_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) {
		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());

}

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void native_flush_tlb_others(const struct cpumask *cpumask,
				 struct mm_struct *mm, unsigned long start,
				 unsigned long end)
{
	struct flush_tlb_info info;

	if (end == 0)
		end = start + PAGE_SIZE;
	info.flush_mm = mm;
	info.flush_start = start;
	info.flush_end = end;

	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
	if (end == TLB_FLUSH_ALL)
		trace_tlb_flush(TLB_REMOTE_SEND_IPI, TLB_FLUSH_ALL);
	else
		trace_tlb_flush(TLB_REMOTE_SEND_IPI,
				(end - start) >> PAGE_SHIFT);

	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);
}

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

	preempt_disable();

	count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);

	/* This is an implicit full barrier that synchronizes with switch_mm. */
	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();
}

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

		goto out;
	}

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

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

		goto out;
	}

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

	/*
         * Both branches below are implicit full barriers (MOV to CR or
         * INVLPG) that synchronize with switch_mm.
         */
	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();
}

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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) {
			/*
                         * Implicit full barrier (INVLPG) that synchronizes
                         * with switch_mm.
                         */
			__flush_tlb_one(start);
		} else {
			leave_mm(smp_processor_id());

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

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

	preempt_enable();
}

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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());
}

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

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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);
}

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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);
	}
}

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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);
}

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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;
}

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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;
}
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late_initcall(create_tlb_single_page_flush_ceiling);

#endif /* CONFIG_SMP */
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22.39%
5
11.11%
alex shi
alex shi
330
21.80%
7
15.56%
glauber de oliveira costa
glauber de oliveira costa
293
19.35%
2
4.44%
rusty russell
rusty russell
57
3.76%
2
4.44%
nadav amit
nadav amit
34
2.25%
2
4.44%
suresh siddha
suresh siddha
25
1.65%
1
2.22%
mel gorman
mel gorman
23
1.52%
3
6.67%
tejun heo
tejun heo
18
1.19%
2
4.44%
brian gerst
brian gerst
11
0.73%
1
2.22%
li shaohua
li shaohua
7
0.46%
1
2.22%
tomoki sekiyama
tomoki sekiyama
5
0.33%
1
2.22%
linus torvalds
linus torvalds
3
0.20%
2
4.44%
jan beulich
jan beulich
3
0.20%
1
2.22%
jeremiah mahler
jeremiah mahler
2
0.13%
1
2.22%
borislav petkov
borislav petkov
2
0.13%
1
2.22%
joonsoo kim
joonsoo kim
1
0.07%
1
2.22%
xiao guangrong
xiao guangrong
1
0.07%
1
2.22%
mike travis
mike travis
1
0.07%
1
2.22%
paul gortmaker
paul gortmaker
1
0.07%
1
2.22%
Total
1514
100.00%
45
100.00%
Directory: arch/x86/mm

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