arch/x86/mm/tlb.c

   1 #include <linux/init.h>
   2
   3 #include <linux/mm.h>
   4 #include <linux/spinlock.h>
   5 #include <linux/smp.h>
   6 #include <linux/interrupt.h>
   7 #include <linux/module.h>
   8 #include <linux/cpu.h>
   9
  10 #include <asm/tlbflush.h>
  11 #include <asm/mmu_context.h>
  12 #include <asm/cache.h>
  13 #include <asm/apic.h>
  14 #include <asm/uv/uv.h>
  15 #include <linux/debugfs.h>
  16
  17 DEFINE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate)
  18                         = { &init_mm, 0, };
  19
  20 /*
  21  *      Smarter SMP flushing macros.
  22  *              c/o Linus Torvalds.
  23  *
  24  *      These mean you can really definitely utterly forget about
  25  *      writing to user space from interrupts. (Its not allowed anyway).
  26  *
  27  *      Optimizations Manfred Spraul <manfred@colorfullife.com>
  28  *
  29  *      More scalable flush, from Andi Kleen
  30  *
  31  *      Implement flush IPI by CALL_FUNCTION_VECTOR, Alex Shi
  32  */
  33
  34 struct flush_tlb_info {
  35         struct mm_struct *flush_mm;
  36         unsigned long flush_start;
  37         unsigned long flush_end;
  38 };
  39
  40 /*
  41  * We cannot call mmdrop() because we are in interrupt context,
  42  * instead update mm->cpu_vm_mask.
  43  */
  44 void leave_mm(int cpu)
  45 {
  46         struct mm_struct *active_mm = this_cpu_read(cpu_tlbstate.active_mm);
  47         if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
  48                 BUG();
  49         if (cpumask_test_cpu(cpu, mm_cpumask(active_mm))) {
  50                 cpumask_clear_cpu(cpu, mm_cpumask(active_mm));
  51                 load_cr3(swapper_pg_dir);
  52         }
  53 }
  54 EXPORT_SYMBOL_GPL(leave_mm);
  55
  56 /*
  57  * The flush IPI assumes that a thread switch happens in this order:
  58  * [cpu0: the cpu that switches]
  59  * 1) switch_mm() either 1a) or 1b)
  60  * 1a) thread switch to a different mm
  61  * 1a1) set cpu_tlbstate to TLBSTATE_OK
  62  *      Now the tlb flush NMI handler flush_tlb_func won't call leave_mm
  63  *      if cpu0 was in lazy tlb mode.
  64  * 1a2) update cpu active_mm
  65  *      Now cpu0 accepts tlb flushes for the new mm.
  66  * 1a3) cpu_set(cpu, new_mm->cpu_vm_mask);
  67  *      Now the other cpus will send tlb flush ipis.
  68  * 1a4) change cr3.
  69  * 1a5) cpu_clear(cpu, old_mm->cpu_vm_mask);
  70  *      Stop ipi delivery for the old mm. This is not synchronized with
  71  *      the other cpus, but flush_tlb_func ignore flush ipis for the wrong
  72  *      mm, and in the worst case we perform a superfluous tlb flush.
  73  * 1b) thread switch without mm change
  74  *      cpu active_mm is correct, cpu0 already handles flush ipis.
  75  * 1b1) set cpu_tlbstate to TLBSTATE_OK
  76  * 1b2) test_and_set the cpu bit in cpu_vm_mask.
  77  *      Atomically set the bit [other cpus will start sending flush ipis],
  78  *      and test the bit.
  79  * 1b3) if the bit was 0: leave_mm was called, flush the tlb.
  80  * 2) switch %%esp, ie current
  81  *
  82  * The interrupt must handle 2 special cases:
  83  * - cr3 is changed before %%esp, ie. it cannot use current->{active_,}mm.
  84  * - the cpu performs speculative tlb reads, i.e. even if the cpu only
  85  *   runs in kernel space, the cpu could load tlb entries for user space
  86  *   pages.
  87  *
  88  * The good news is that cpu_tlbstate is local to each cpu, no
  89  * write/read ordering problems.
  90  */
  91
  92 /*
  93  * TLB flush funcation:
  94  * 1) Flush the tlb entries if the cpu uses the mm that's being flushed.
  95  * 2) Leave the mm if we are in the lazy tlb mode.
  96  */
  97 static void flush_tlb_func(void *info)
  98 {
  99         struct flush_tlb_info *f = info;
 100
 101         inc_irq_stat(irq_tlb_count);
 102
 103         if (f->flush_mm != this_cpu_read(cpu_tlbstate.active_mm))
 104                 return;
 105
 106         count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
 107         if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK) {
 108                 if (f->flush_end == TLB_FLUSH_ALL)
 109                         local_flush_tlb();
 110                 else if (!f->flush_end)
 111                         __flush_tlb_single(f->flush_start);
 112                 else {
 113                         unsigned long addr;
 114                         addr = f->flush_start;
 115                         while (addr < f->flush_end) {
 116                                 __flush_tlb_single(addr);
 117                                 addr += PAGE_SIZE;
 118                         }
 119                 }
 120         } else
 121                 leave_mm(smp_processor_id());
 122
 123 }
 124
 125 void native_flush_tlb_others(const struct cpumask *cpumask,
 126                                  struct mm_struct *mm, unsigned long start,
 127                                  unsigned long end)
 128 {
 129         struct flush_tlb_info info;
 130         info.flush_mm = mm;
 131         info.flush_start = start;
 132         info.flush_end = end;
 133
 134         count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
 135         if (is_uv_system()) {
 136                 unsigned int cpu;
 137
 138                 cpu = smp_processor_id();
 139                 cpumask = uv_flush_tlb_others(cpumask, mm, start, end, cpu);
 140                 if (cpumask)
 141                         smp_call_function_many(cpumask, flush_tlb_func,
 142                                                                 &info, 1);
 143                 return;
 144         }
 145         smp_call_function_many(cpumask, flush_tlb_func, &info, 1);
 146 }
 147
 148 void flush_tlb_current_task(void)
 149 {
 150         struct mm_struct *mm = current->mm;
 151
 152         preempt_disable();
 153
 154         count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
 155         local_flush_tlb();
 156         if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
 157                 flush_tlb_others(mm_cpumask(mm), mm, 0UL, TLB_FLUSH_ALL);
 158         preempt_enable();
 159 }
 160
 161 void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
 162                                 unsigned long end, unsigned long vmflag)
 163 {
 164         unsigned long addr;
 165         unsigned act_entries, tlb_entries = 0;
 166         unsigned long nr_base_pages;
 167
 168         preempt_disable();
 169         if (current->active_mm != mm)
 170                 goto flush_all;
 171
 172         if (!current->mm) {
 173                 leave_mm(smp_processor_id());
 174                 goto flush_all;
 175         }
 176
 177         if (end == TLB_FLUSH_ALL || tlb_flushall_shift == -1
 178                                         || vmflag & VM_HUGETLB) {
 179                 local_flush_tlb();
 180                 goto flush_all;
 181         }
 182
 183         /* In modern CPU, last level tlb used for both data/ins */
 184         if (vmflag & VM_EXEC)
 185                 tlb_entries = tlb_lli_4k[ENTRIES];
 186         else
 187                 tlb_entries = tlb_lld_4k[ENTRIES];
 188
 189         /* Assume all of TLB entries was occupied by this task */
 190         act_entries = tlb_entries >> tlb_flushall_shift;
 191         act_entries = mm->total_vm > act_entries ? act_entries : mm->total_vm;
 192         nr_base_pages = (end - start) >> PAGE_SHIFT;
 193
 194         /* tlb_flushall_shift is on balance point, details in commit log */
 195         if (nr_base_pages > act_entries) {
 196                 count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
 197                 local_flush_tlb();
 198         } else {
 199                 /* flush range by one by one 'invlpg' */
 200                 for (addr = start; addr < end;  addr += PAGE_SIZE) {
 201                         count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ONE);
 202                         __flush_tlb_single(addr);
 203                 }
 204
 205                 if (cpumask_any_but(mm_cpumask(mm),
 206                                 smp_processor_id()) < nr_cpu_ids)
 207                         flush_tlb_others(mm_cpumask(mm), mm, start, end);
 208                 preempt_enable();
 209                 return;
 210         }
 211
 212 flush_all:
 213         if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
 214                 flush_tlb_others(mm_cpumask(mm), mm, 0UL, TLB_FLUSH_ALL);
 215         preempt_enable();
 216 }
 217
 218 void flush_tlb_page(struct vm_area_struct *vma, unsigned long start)
 219 {
 220         struct mm_struct *mm = vma->vm_mm;
 221
 222         preempt_disable();
 223
 224         if (current->active_mm == mm) {
 225                 if (current->mm)
 226                         __flush_tlb_one(start);
 227                 else
 228                         leave_mm(smp_processor_id());
 229         }
 230
 231         if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
 232                 flush_tlb_others(mm_cpumask(mm), mm, start, 0UL);
 233
 234         preempt_enable();
 235 }
 236
 237 static void do_flush_tlb_all(void *info)
 238 {
 239         count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
 240         __flush_tlb_all();
 241         if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_LAZY)
 242                 leave_mm(smp_processor_id());
 243 }
 244
 245 void flush_tlb_all(void)
 246 {
 247         count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
 248         on_each_cpu(do_flush_tlb_all, NULL, 1);
 249 }
 250
 251 static void do_kernel_range_flush(void *info)
 252 {
 253         struct flush_tlb_info *f = info;
 254         unsigned long addr;
 255
 256         /* flush range by one by one 'invlpg' */
 257         for (addr = f->flush_start; addr < f->flush_end; addr += PAGE_SIZE)
 258                 __flush_tlb_single(addr);
 259 }
 260
 261 void flush_tlb_kernel_range(unsigned long start, unsigned long end)
 262 {
 263         unsigned act_entries;
 264         struct flush_tlb_info info;
 265
 266         /* In modern CPU, last level tlb used for both data/ins */
 267         act_entries = tlb_lld_4k[ENTRIES];
 268
 269         /* Balance as user space task's flush, a bit conservative */
 270         if (end == TLB_FLUSH_ALL || tlb_flushall_shift == -1 ||
 271                 (end - start) >> PAGE_SHIFT > act_entries >> tlb_flushall_shift)
 272
 273                 on_each_cpu(do_flush_tlb_all, NULL, 1);
 274         else {
 275                 info.flush_start = start;
 276                 info.flush_end = end;
 277                 on_each_cpu(do_kernel_range_flush, &info, 1);
 278         }
 279 }
 280
 281 #ifdef CONFIG_DEBUG_TLBFLUSH
 282 static ssize_t tlbflush_read_file(struct file *file, char __user *user_buf,
 283                              size_t count, loff_t *ppos)
 284 {
 285         char buf[32];
 286         unsigned int len;
 287
 288         len = sprintf(buf, "%hd\n", tlb_flushall_shift);
 289         return simple_read_from_buffer(user_buf, count, ppos, buf, len);
 290 }
 291
 292 static ssize_t tlbflush_write_file(struct file *file,
 293                  const char __user *user_buf, size_t count, loff_t *ppos)
 294 {
 295         char buf[32];
 296         ssize_t len;
 297         s8 shift;
 298
 299         len = min(count, sizeof(buf) - 1);
 300         if (copy_from_user(buf, user_buf, len))
 301                 return -EFAULT;
 302
 303         buf[len] = '\0';
 304         if (kstrtos8(buf, 0, &shift))
 305                 return -EINVAL;
 306
 307         if (shift < -1 || shift >= BITS_PER_LONG)
 308                 return -EINVAL;
 309
 310         tlb_flushall_shift = shift;
 311         return count;
 312 }
 313
 314 static const struct file_operations fops_tlbflush = {
 315         .read = tlbflush_read_file,
 316         .write = tlbflush_write_file,
 317         .llseek = default_llseek,
 318 };
 319
 320 static int __init create_tlb_flushall_shift(void)
 321 {
 322         debugfs_create_file("tlb_flushall_shift", S_IRUSR | S_IWUSR,
 323                             arch_debugfs_dir, NULL, &fops_tlbflush);
 324         return 0;
 325 }
 326 late_initcall(create_tlb_flushall_shift);
 327 #endif