arch/x86/kvm/page_track.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Support KVM gust page tracking
   4  *
   5  * This feature allows us to track page access in guest. Currently, only
   6  * write access is tracked.
   7  *
   8  * Copyright(C) 2015 Intel Corporation.
   9  *
  10  * Author:
  11  *   Xiao Guangrong <guangrong.xiao@linux.intel.com>
  12  */
  13
  14 #include <linux/kvm_host.h>
  15 #include <linux/rculist.h>
  16
  17 #include <asm/kvm_host.h>
  18 #include <asm/kvm_page_track.h>
  19
  20 #include "mmu.h"
  21
  22 void kvm_page_track_free_memslot(struct kvm_memory_slot *free,
  23                                  struct kvm_memory_slot *dont)
  24 {
  25         int i;
  26
  27         for (i = 0; i < KVM_PAGE_TRACK_MAX; i++)
  28                 if (!dont || free->arch.gfn_track[i] !=
  29                       dont->arch.gfn_track[i]) {
  30                         kvfree(free->arch.gfn_track[i]);
  31                         free->arch.gfn_track[i] = NULL;
  32                 }
  33 }
  34
  35 int kvm_page_track_create_memslot(struct kvm_memory_slot *slot,
  36                                   unsigned long npages)
  37 {
  38         int  i;
  39
  40         for (i = 0; i < KVM_PAGE_TRACK_MAX; i++) {
  41                 slot->arch.gfn_track[i] =
  42                         kvcalloc(npages, sizeof(*slot->arch.gfn_track[i]),
  43                                  GFP_KERNEL_ACCOUNT);
  44                 if (!slot->arch.gfn_track[i])
  45                         goto track_free;
  46         }
  47
  48         return 0;
  49
  50 track_free:
  51         kvm_page_track_free_memslot(slot, NULL);
  52         return -ENOMEM;
  53 }
  54
  55 static inline bool page_track_mode_is_valid(enum kvm_page_track_mode mode)
  56 {
  57         if (mode < 0 || mode >= KVM_PAGE_TRACK_MAX)
  58                 return false;
  59
  60         return true;
  61 }
  62
  63 static void update_gfn_track(struct kvm_memory_slot *slot, gfn_t gfn,
  64                              enum kvm_page_track_mode mode, short count)
  65 {
  66         int index, val;
  67
  68         index = gfn_to_index(gfn, slot->base_gfn, PT_PAGE_TABLE_LEVEL);
  69
  70         val = slot->arch.gfn_track[mode][index];
  71
  72         if (WARN_ON(val + count < 0 || val + count > USHRT_MAX))
  73                 return;
  74
  75         slot->arch.gfn_track[mode][index] += count;
  76 }
  77
  78 /*
  79  * add guest page to the tracking pool so that corresponding access on that
  80  * page will be intercepted.
  81  *
  82  * It should be called under the protection both of mmu-lock and kvm->srcu
  83  * or kvm->slots_lock.
  84  *
  85  * @kvm: the guest instance we are interested in.
  86  * @slot: the @gfn belongs to.
  87  * @gfn: the guest page.
  88  * @mode: tracking mode, currently only write track is supported.
  89  */
  90 void kvm_slot_page_track_add_page(struct kvm *kvm,
  91                                   struct kvm_memory_slot *slot, gfn_t gfn,
  92                                   enum kvm_page_track_mode mode)
  93 {
  94
  95         if (WARN_ON(!page_track_mode_is_valid(mode)))
  96                 return;
  97
  98         update_gfn_track(slot, gfn, mode, 1);
  99
 100         /*
 101          * new track stops large page mapping for the
 102          * tracked page.
 103          */
 104         kvm_mmu_gfn_disallow_lpage(slot, gfn);
 105
 106         if (mode == KVM_PAGE_TRACK_WRITE)
 107                 if (kvm_mmu_slot_gfn_write_protect(kvm, slot, gfn))
 108                         kvm_flush_remote_tlbs(kvm);
 109 }
 110 EXPORT_SYMBOL_GPL(kvm_slot_page_track_add_page);
 111
 112 /*
 113  * remove the guest page from the tracking pool which stops the interception
 114  * of corresponding access on that page. It is the opposed operation of
 115  * kvm_slot_page_track_add_page().
 116  *
 117  * It should be called under the protection both of mmu-lock and kvm->srcu
 118  * or kvm->slots_lock.
 119  *
 120  * @kvm: the guest instance we are interested in.
 121  * @slot: the @gfn belongs to.
 122  * @gfn: the guest page.
 123  * @mode: tracking mode, currently only write track is supported.
 124  */
 125 void kvm_slot_page_track_remove_page(struct kvm *kvm,
 126                                      struct kvm_memory_slot *slot, gfn_t gfn,
 127                                      enum kvm_page_track_mode mode)
 128 {
 129         if (WARN_ON(!page_track_mode_is_valid(mode)))
 130                 return;
 131
 132         update_gfn_track(slot, gfn, mode, -1);
 133
 134         /*
 135          * allow large page mapping for the tracked page
 136          * after the tracker is gone.
 137          */
 138         kvm_mmu_gfn_allow_lpage(slot, gfn);
 139 }
 140 EXPORT_SYMBOL_GPL(kvm_slot_page_track_remove_page);
 141
 142 /*
 143  * check if the corresponding access on the specified guest page is tracked.
 144  */
 145 bool kvm_page_track_is_active(struct kvm_vcpu *vcpu, gfn_t gfn,
 146                               enum kvm_page_track_mode mode)
 147 {
 148         struct kvm_memory_slot *slot;
 149         int index;
 150
 151         if (WARN_ON(!page_track_mode_is_valid(mode)))
 152                 return false;
 153
 154         slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
 155         if (!slot)
 156                 return false;
 157
 158         index = gfn_to_index(gfn, slot->base_gfn, PT_PAGE_TABLE_LEVEL);
 159         return !!READ_ONCE(slot->arch.gfn_track[mode][index]);
 160 }
 161
 162 void kvm_page_track_cleanup(struct kvm *kvm)
 163 {
 164         struct kvm_page_track_notifier_head *head;
 165
 166         head = &kvm->arch.track_notifier_head;
 167         cleanup_srcu_struct(&head->track_srcu);
 168 }
 169
 170 void kvm_page_track_init(struct kvm *kvm)
 171 {
 172         struct kvm_page_track_notifier_head *head;
 173
 174         head = &kvm->arch.track_notifier_head;
 175         init_srcu_struct(&head->track_srcu);
 176         INIT_HLIST_HEAD(&head->track_notifier_list);
 177 }
 178
 179 /*
 180  * register the notifier so that event interception for the tracked guest
 181  * pages can be received.
 182  */
 183 void
 184 kvm_page_track_register_notifier(struct kvm *kvm,
 185                                  struct kvm_page_track_notifier_node *n)
 186 {
 187         struct kvm_page_track_notifier_head *head;
 188
 189         head = &kvm->arch.track_notifier_head;
 190
 191         spin_lock(&kvm->mmu_lock);
 192         hlist_add_head_rcu(&n->node, &head->track_notifier_list);
 193         spin_unlock(&kvm->mmu_lock);
 194 }
 195 EXPORT_SYMBOL_GPL(kvm_page_track_register_notifier);
 196
 197 /*
 198  * stop receiving the event interception. It is the opposed operation of
 199  * kvm_page_track_register_notifier().
 200  */
 201 void
 202 kvm_page_track_unregister_notifier(struct kvm *kvm,
 203                                    struct kvm_page_track_notifier_node *n)
 204 {
 205         struct kvm_page_track_notifier_head *head;
 206
 207         head = &kvm->arch.track_notifier_head;
 208
 209         spin_lock(&kvm->mmu_lock);
 210         hlist_del_rcu(&n->node);
 211         spin_unlock(&kvm->mmu_lock);
 212         synchronize_srcu(&head->track_srcu);
 213 }
 214 EXPORT_SYMBOL_GPL(kvm_page_track_unregister_notifier);
 215
 216 /*
 217  * Notify the node that write access is intercepted and write emulation is
 218  * finished at this time.
 219  *
 220  * The node should figure out if the written page is the one that node is
 221  * interested in by itself.
 222  */
 223 void kvm_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
 224                           int bytes)
 225 {
 226         struct kvm_page_track_notifier_head *head;
 227         struct kvm_page_track_notifier_node *n;
 228         int idx;
 229
 230         head = &vcpu->kvm->arch.track_notifier_head;
 231
 232         if (hlist_empty(&head->track_notifier_list))
 233                 return;
 234
 235         idx = srcu_read_lock(&head->track_srcu);
 236         hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
 237                 if (n->track_write)
 238                         n->track_write(vcpu, gpa, new, bytes, n);
 239         srcu_read_unlock(&head->track_srcu, idx);
 240 }
 241
 242 /*
 243  * Notify the node that memory slot is being removed or moved so that it can
 244  * drop write-protection for the pages in the memory slot.
 245  *
 246  * The node should figure out it has any write-protected pages in this slot
 247  * by itself.
 248  */
 249 void kvm_page_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot *slot)
 250 {
 251         struct kvm_page_track_notifier_head *head;
 252         struct kvm_page_track_notifier_node *n;
 253         int idx;
 254
 255         head = &kvm->arch.track_notifier_head;
 256
 257         if (hlist_empty(&head->track_notifier_list))
 258                 return;
 259
 260         idx = srcu_read_lock(&head->track_srcu);
 261         hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
 262                 if (n->track_flush_slot)
 263                         n->track_flush_slot(kvm, slot, n);
 264         srcu_read_unlock(&head->track_srcu, idx);
 265 }