arch/x86/kernel/kvm.c

   1 /*
   2  * KVM paravirt_ops implementation
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  17  *
  18  * Copyright (C) 2007, Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
  19  * Copyright IBM Corporation, 2007
  20  *   Authors: Anthony Liguori <aliguori@us.ibm.com>
  21  */
  22
  23 #include <linux/module.h>
  24 #include <linux/kernel.h>
  25 #include <linux/kvm_para.h>
  26 #include <linux/cpu.h>
  27 #include <linux/mm.h>
  28 #include <linux/highmem.h>
  29 #include <linux/hardirq.h>
  30 #include <linux/notifier.h>
  31 #include <linux/reboot.h>
  32 #include <linux/hash.h>
  33 #include <linux/sched.h>
  34 #include <linux/slab.h>
  35 #include <linux/kprobes.h>
  36 #include <asm/timer.h>
  37 #include <asm/cpu.h>
  38 #include <asm/traps.h>
  39 #include <asm/desc.h>
  40 #include <asm/tlbflush.h>
  41
  42 static int kvmapf = 1;
  43
  44 static int parse_no_kvmapf(char *arg)
  45 {
  46         kvmapf = 0;
  47         return 0;
  48 }
  49
  50 early_param("no-kvmapf", parse_no_kvmapf);
  51
  52 static int steal_acc = 1;
  53 static int parse_no_stealacc(char *arg)
  54 {
  55         steal_acc = 0;
  56         return 0;
  57 }
  58
  59 early_param("no-steal-acc", parse_no_stealacc);
  60
  61 static DEFINE_PER_CPU(struct kvm_vcpu_pv_apf_data, apf_reason) __aligned(64);
  62 static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);
  63 static int has_steal_clock = 0;
  64
  65 /*
  66  * No need for any "IO delay" on KVM
  67  */
  68 static void kvm_io_delay(void)
  69 {
  70 }
  71
  72 #define KVM_TASK_SLEEP_HASHBITS 8
  73 #define KVM_TASK_SLEEP_HASHSIZE (1<<KVM_TASK_SLEEP_HASHBITS)
  74
  75 struct kvm_task_sleep_node {
  76         struct hlist_node link;
  77         wait_queue_head_t wq;
  78         u32 token;
  79         int cpu;
  80         bool halted;
  81         struct mm_struct *mm;
  82 };
  83
  84 static struct kvm_task_sleep_head {
  85         spinlock_t lock;
  86         struct hlist_head list;
  87 } async_pf_sleepers[KVM_TASK_SLEEP_HASHSIZE];
  88
  89 static struct kvm_task_sleep_node *_find_apf_task(struct kvm_task_sleep_head *b,
  90                                                   u32 token)
  91 {
  92         struct hlist_node *p;
  93
  94         hlist_for_each(p, &b->list) {
  95                 struct kvm_task_sleep_node *n =
  96                         hlist_entry(p, typeof(*n), link);
  97                 if (n->token == token)
  98                         return n;
  99         }
 100
 101         return NULL;
 102 }
 103
 104 void kvm_async_pf_task_wait(u32 token)
 105 {
 106         u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
 107         struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
 108         struct kvm_task_sleep_node n, *e;
 109         DEFINE_WAIT(wait);
 110         int cpu, idle;
 111
 112         cpu = get_cpu();
 113         idle = idle_cpu(cpu);
 114         put_cpu();
 115
 116         spin_lock(&b->lock);
 117         e = _find_apf_task(b, token);
 118         if (e) {
 119                 /* dummy entry exist -> wake up was delivered ahead of PF */
 120                 hlist_del(&e->link);
 121                 kfree(e);
 122                 spin_unlock(&b->lock);
 123                 return;
 124         }
 125
 126         n.token = token;
 127         n.cpu = smp_processor_id();
 128         n.mm = current->active_mm;
 129         n.halted = idle || preempt_count() > 1;
 130         atomic_inc(&n.mm->mm_count);
 131         init_waitqueue_head(&n.wq);
 132         hlist_add_head(&n.link, &b->list);
 133         spin_unlock(&b->lock);
 134
 135         for (;;) {
 136                 if (!n.halted)
 137                         prepare_to_wait(&n.wq, &wait, TASK_UNINTERRUPTIBLE);
 138                 if (hlist_unhashed(&n.link))
 139                         break;
 140
 141                 if (!n.halted) {
 142                         local_irq_enable();
 143                         schedule();
 144                         local_irq_disable();
 145                 } else {
 146                         /*
 147                          * We cannot reschedule. So halt.
 148                          */
 149                         native_safe_halt();
 150                         local_irq_disable();
 151                 }
 152         }
 153         if (!n.halted)
 154                 finish_wait(&n.wq, &wait);
 155
 156         return;
 157 }
 158 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wait);
 159
 160 static void apf_task_wake_one(struct kvm_task_sleep_node *n)
 161 {
 162         hlist_del_init(&n->link);
 163         if (!n->mm)
 164                 return;
 165         mmdrop(n->mm);
 166         if (n->halted)
 167                 smp_send_reschedule(n->cpu);
 168         else if (waitqueue_active(&n->wq))
 169                 wake_up(&n->wq);
 170 }
 171
 172 static void apf_task_wake_all(void)
 173 {
 174         int i;
 175
 176         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++) {
 177                 struct hlist_node *p, *next;
 178                 struct kvm_task_sleep_head *b = &async_pf_sleepers[i];
 179                 spin_lock(&b->lock);
 180                 hlist_for_each_safe(p, next, &b->list) {
 181                         struct kvm_task_sleep_node *n =
 182                                 hlist_entry(p, typeof(*n), link);
 183                         if (n->cpu == smp_processor_id())
 184                                 apf_task_wake_one(n);
 185                 }
 186                 spin_unlock(&b->lock);
 187         }
 188 }
 189
 190 void kvm_async_pf_task_wake(u32 token)
 191 {
 192         u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS);
 193         struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
 194         struct kvm_task_sleep_node *n;
 195
 196         if (token == ~0) {
 197                 apf_task_wake_all();
 198                 return;
 199         }
 200
 201 again:
 202         spin_lock(&b->lock);
 203         n = _find_apf_task(b, token);
 204         if (!n) {
 205                 /*
 206                  * async PF was not yet handled.
 207                  * Add dummy entry for the token.
 208                  */
 209                 n = kmalloc(sizeof(*n), GFP_ATOMIC);
 210                 if (!n) {
 211                         /*
 212                          * Allocation failed! Busy wait while other cpu
 213                          * handles async PF.
 214                          */
 215                         spin_unlock(&b->lock);
 216                         cpu_relax();
 217                         goto again;
 218                 }
 219                 n->token = token;
 220                 n->cpu = smp_processor_id();
 221                 n->mm = NULL;
 222                 init_waitqueue_head(&n->wq);
 223                 hlist_add_head(&n->link, &b->list);
 224         } else
 225                 apf_task_wake_one(n);
 226         spin_unlock(&b->lock);
 227         return;
 228 }
 229 EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake);
 230
 231 u32 kvm_read_and_reset_pf_reason(void)
 232 {
 233         u32 reason = 0;
 234
 235         if (__get_cpu_var(apf_reason).enabled) {
 236                 reason = __get_cpu_var(apf_reason).reason;
 237                 __get_cpu_var(apf_reason).reason = 0;
 238         }
 239
 240         return reason;
 241 }
 242 EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason);
 243
 244 dotraplinkage void __kprobes
 245 do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
 246 {
 247         switch (kvm_read_and_reset_pf_reason()) {
 248         default:
 249                 do_page_fault(regs, error_code);
 250                 break;
 251         case KVM_PV_REASON_PAGE_NOT_PRESENT:
 252                 /* page is swapped out by the host. */
 253                 kvm_async_pf_task_wait((u32)read_cr2());
 254                 break;
 255         case KVM_PV_REASON_PAGE_READY:
 256                 kvm_async_pf_task_wake((u32)read_cr2());
 257                 break;
 258         }
 259 }
 260
 261 static void __init paravirt_ops_setup(void)
 262 {
 263         pv_info.name = "KVM";
 264         pv_info.paravirt_enabled = 1;
 265
 266         if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
 267                 pv_cpu_ops.io_delay = kvm_io_delay;
 268
 269 #ifdef CONFIG_X86_IO_APIC
 270         no_timer_check = 1;
 271 #endif
 272 }
 273
 274 static void kvm_register_steal_time(void)
 275 {
 276         int cpu = smp_processor_id();
 277         struct kvm_steal_time *st = &per_cpu(steal_time, cpu);
 278
 279         if (!has_steal_clock)
 280                 return;
 281
 282         memset(st, 0, sizeof(*st));
 283
 284         wrmsrl(MSR_KVM_STEAL_TIME, (__pa(st) | KVM_MSR_ENABLED));
 285         printk(KERN_INFO "kvm-stealtime: cpu %d, msr %lx\n",
 286                 cpu, __pa(st));
 287 }
 288
 289 void __cpuinit kvm_guest_cpu_init(void)
 290 {
 291         if (!kvm_para_available())
 292                 return;
 293
 294         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
 295                 u64 pa = __pa(&__get_cpu_var(apf_reason));
 296
 297 #ifdef CONFIG_PREEMPT
 298                 pa |= KVM_ASYNC_PF_SEND_ALWAYS;
 299 #endif
 300                 wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
 301                 __get_cpu_var(apf_reason).enabled = 1;
 302                 printk(KERN_INFO"KVM setup async PF for cpu %d\n",
 303                        smp_processor_id());
 304         }
 305
 306         if (has_steal_clock)
 307                 kvm_register_steal_time();
 308 }
 309
 310 static void kvm_pv_disable_apf(void *unused)
 311 {
 312         if (!__get_cpu_var(apf_reason).enabled)
 313                 return;
 314
 315         wrmsrl(MSR_KVM_ASYNC_PF_EN, 0);
 316         __get_cpu_var(apf_reason).enabled = 0;
 317
 318         printk(KERN_INFO"Unregister pv shared memory for cpu %d\n",
 319                smp_processor_id());
 320 }
 321
 322 static int kvm_pv_reboot_notify(struct notifier_block *nb,
 323                                 unsigned long code, void *unused)
 324 {
 325         if (code == SYS_RESTART)
 326                 on_each_cpu(kvm_pv_disable_apf, NULL, 1);
 327         return NOTIFY_DONE;
 328 }
 329
 330 static struct notifier_block kvm_pv_reboot_nb = {
 331         .notifier_call = kvm_pv_reboot_notify,
 332 };
 333
 334 static u64 kvm_steal_clock(int cpu)
 335 {
 336         u64 steal;
 337         struct kvm_steal_time *src;
 338         int version;
 339
 340         src = &per_cpu(steal_time, cpu);
 341         do {
 342                 version = src->version;
 343                 rmb();
 344                 steal = src->steal;
 345                 rmb();
 346         } while ((version & 1) || (version != src->version));
 347
 348         return steal;
 349 }
 350
 351 void kvm_disable_steal_time(void)
 352 {
 353         if (!has_steal_clock)
 354                 return;
 355
 356         wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
 357 }
 358
 359 #ifdef CONFIG_SMP
 360 static void __init kvm_smp_prepare_boot_cpu(void)
 361 {
 362 #ifdef CONFIG_KVM_CLOCK
 363         WARN_ON(kvm_register_clock("primary cpu clock"));
 364 #endif
 365         kvm_guest_cpu_init();
 366         native_smp_prepare_boot_cpu();
 367 }
 368
 369 static void __cpuinit kvm_guest_cpu_online(void *dummy)
 370 {
 371         kvm_guest_cpu_init();
 372 }
 373
 374 static void kvm_guest_cpu_offline(void *dummy)
 375 {
 376         kvm_disable_steal_time();
 377         kvm_pv_disable_apf(NULL);
 378         apf_task_wake_all();
 379 }
 380
 381 static int __cpuinit kvm_cpu_notify(struct notifier_block *self,
 382                                     unsigned long action, void *hcpu)
 383 {
 384         int cpu = (unsigned long)hcpu;
 385         switch (action) {
 386         case CPU_ONLINE:
 387         case CPU_DOWN_FAILED:
 388         case CPU_ONLINE_FROZEN:
 389                 smp_call_function_single(cpu, kvm_guest_cpu_online, NULL, 0);
 390                 break;
 391         case CPU_DOWN_PREPARE:
 392         case CPU_DOWN_PREPARE_FROZEN:
 393                 smp_call_function_single(cpu, kvm_guest_cpu_offline, NULL, 1);
 394                 break;
 395         default:
 396                 break;
 397         }
 398         return NOTIFY_OK;
 399 }
 400
 401 static struct notifier_block __cpuinitdata kvm_cpu_notifier = {
 402         .notifier_call  = kvm_cpu_notify,
 403 };
 404 #endif
 405
 406 static void __init kvm_apf_trap_init(void)
 407 {
 408         set_intr_gate(14, &async_page_fault);
 409 }
 410
 411 void __init kvm_guest_init(void)
 412 {
 413         int i;
 414
 415         if (!kvm_para_available())
 416                 return;
 417
 418         paravirt_ops_setup();
 419         register_reboot_notifier(&kvm_pv_reboot_nb);
 420         for (i = 0; i < KVM_TASK_SLEEP_HASHSIZE; i++)
 421                 spin_lock_init(&async_pf_sleepers[i].lock);
 422         if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
 423                 x86_init.irqs.trap_init = kvm_apf_trap_init;
 424
 425         if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
 426                 has_steal_clock = 1;
 427                 pv_time_ops.steal_clock = kvm_steal_clock;
 428         }
 429
 430 #ifdef CONFIG_SMP
 431         smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
 432         register_cpu_notifier(&kvm_cpu_notifier);
 433 #else
 434         kvm_guest_cpu_init();
 435 #endif
 436 }
 437
 438 static __init int activate_jump_labels(void)
 439 {
 440         if (has_steal_clock) {
 441                 static_key_slow_inc(&paravirt_steal_enabled);
 442                 if (steal_acc)
 443                         static_key_slow_inc(&paravirt_steal_rq_enabled);
 444         }
 445
 446         return 0;
 447 }
 448 arch_initcall(activate_jump_labels);