@@ -128,6 +128,7 @@ static inline gfn_t gfn_to_index(gfn_t gfn, gfn_t base_gfn, int level)
#define KVM_MIN_ALLOC_MMU_PAGES 64
#define KVM_MMU_HASH_SHIFT 12
#define KVM_NUM_MMU_PAGES (1 << KVM_MMU_HASH_SHIFT)
+#define KVM_MMU_SP_ENTRY_NR 512
#define KVM_MIN_FREE_MMU_PAGES 5
#define KVM_REFILL_PAGES 25
#define KVM_MAX_CPUID_ENTRIES 80
@@ -331,13 +332,15 @@ struct kvm_mmu_page {
gfn_t *gfns;
int root_count; /* Currently serving as active root */
unsigned int unsync_children;
+ unsigned int possible_writable_sptes;
struct kvm_rmap_head parent_ptes; /* rmap pointers to parent sptes */
/* The page is obsolete if mmu_valid_gen != kvm->arch.mmu_valid_gen. */
unsigned long mmu_valid_gen;
- DECLARE_BITMAP(unsync_child_bitmap, 512);
+ DECLARE_BITMAP(unsync_child_bitmap, KVM_MMU_SP_ENTRY_NR);
+ DECLARE_BITMAP(possible_writable_spte_bitmap, KVM_MMU_SP_ENTRY_NR);
#ifdef CONFIG_X86_32
/*
* Used out of the mmu-lock to avoid reading spte values while an
@@ -718,6 +718,49 @@ static bool is_dirty_spte(u64 spte)
return dirty_mask ? spte & dirty_mask : spte & PT_WRITABLE_MASK;
}
+static bool is_possible_writable_spte(u64 spte)
+{
+ if (!is_shadow_present_pte(spte))
+ return false;
+
+ if (is_writable_pte(spte))
+ return true;
+
+ if (spte_can_locklessly_be_made_writable(spte))
+ return true;
+
+ /*
+ * although is_access_track_spte() sptes can be updated out of
+ * mmu-lock, we need not take them into account as access_track
+ * drops writable bit for them
+ */
+ return false;
+}
+
+static void
+mmu_log_possible_writable_spte(u64 *sptep, u64 old_spte, u64 new_spte)
+{
+ struct kvm_mmu_page *sp = page_header(__pa(sptep));
+ bool old_state, new_state;
+
+ old_state = is_possible_writable_spte(old_spte);
+ new_state = is_possible_writable_spte(new_spte);
+
+ if (old_state == new_state)
+ return;
+
+ /* a possible writable spte is dropped */
+ if (old_state) {
+ sp->possible_writable_sptes--;
+ __clear_bit(sptep - sp->spt, sp->possible_writable_spte_bitmap);
+ return;
+ }
+
+ /* a new possible writable spte is set */
+ sp->possible_writable_sptes++;
+ __set_bit(sptep - sp->spt, sp->possible_writable_spte_bitmap);
+}
+
/* Rules for using mmu_spte_set:
* Set the sptep from nonpresent to present.
* Note: the sptep being assigned *must* be either not present
@@ -728,6 +771,7 @@ static void mmu_spte_set(u64 *sptep, u64 new_spte)
{
WARN_ON(is_shadow_present_pte(*sptep));
__set_spte(sptep, new_spte);
+ mmu_log_possible_writable_spte(sptep, 0ull, new_spte);
}
/*
@@ -751,7 +795,7 @@ static u64 mmu_spte_update_no_track(u64 *sptep, u64 new_spte)
old_spte = __update_clear_spte_slow(sptep, new_spte);
WARN_ON(spte_to_pfn(old_spte) != spte_to_pfn(new_spte));
-
+ mmu_log_possible_writable_spte(sptep, old_spte, new_spte);
return old_spte;
}
@@ -817,6 +861,8 @@ static int mmu_spte_clear_track_bits(u64 *sptep)
else
old_spte = __update_clear_spte_slow(sptep, 0ull);
+ mmu_log_possible_writable_spte(sptep, old_spte, 0ull);
+
if (!is_shadow_present_pte(old_spte))
return 0;
@@ -845,7 +891,10 @@ static int mmu_spte_clear_track_bits(u64 *sptep)
*/
static void mmu_spte_clear_no_track(u64 *sptep)
{
+ u64 old_spte = *sptep;
+
__update_clear_spte_fast(sptep, 0ull);
+ mmu_log_possible_writable_spte(sptep, old_spte, 0ull);
}
static u64 mmu_spte_get_lockless(u64 *sptep)
@@ -2140,7 +2189,7 @@ static int __mmu_unsync_walk(struct kvm_mmu_page *sp,
{
int i, ret, nr_unsync_leaf = 0;
- for_each_set_bit(i, sp->unsync_child_bitmap, 512) {
+ for_each_set_bit(i, sp->unsync_child_bitmap, KVM_MMU_SP_ENTRY_NR) {
struct kvm_mmu_page *child;
u64 ent = sp->spt[i];