KVM: MMU: use page array in unsync walk

Instead of invoking the handler directly collect pages into
an array so the caller can work with it.

Simplifies TLB flush collapsing.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

2 files changed, 141 insertions, 56 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f58f7ebdea81..93d0aed35880 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -200,7 +200,7 @@ struct kvm_mmu_page {
         int multimapped;         /* More than one parent_pte? */
         int root_count;          /* Currently serving as active root */
         bool unsync;
-        bool unsync_children;
+        unsigned int unsync_children;
         union {
                 u64 *parent_pte;               /* !multimapped */
                 struct hlist_head parent_ptes; /* multimapped, kvm_pte_chain */
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index dd20b199a7c0..7ce92f78f337 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -908,8 +908,9 @@ static void kvm_mmu_update_unsync_bitmap(u64 *spte)
         struct kvm_mmu_page *sp = page_header(__pa(spte));
 
         index = spte - sp->spt;
-        __set_bit(index, sp->unsync_child_bitmap);
-        sp->unsync_children = 1;
+        if (!__test_and_set_bit(index, sp->unsync_child_bitmap))
+                sp->unsync_children++;
+        WARN_ON(!sp->unsync_children);
 }
 
 static void kvm_mmu_update_parents_unsync(struct kvm_mmu_page *sp)
@@ -936,7 +937,6 @@ static void kvm_mmu_update_parents_unsync(struct kvm_mmu_page *sp)
 
 static int unsync_walk_fn(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
 {
-        sp->unsync_children = 1;
         kvm_mmu_update_parents_unsync(sp);
         return 1;
 }
@@ -967,18 +967,41 @@ static void nonpaging_invlpg(struct kvm_vcpu *vcpu, gva_t gva)
 {
 }
 
+#define KVM_PAGE_ARRAY_NR 16
+
+struct kvm_mmu_pages {
+        struct mmu_page_and_offset {
+                struct kvm_mmu_page *sp;
+                unsigned int idx;
+        } page[KVM_PAGE_ARRAY_NR];
+        unsigned int nr;
+};
+
 #define for_each_unsync_children(bitmap, idx)           \
         for (idx = find_first_bit(bitmap, 512);         \
              idx < 512;                                 \
              idx = find_next_bit(bitmap, 512, idx+1))
 
-static int mmu_unsync_walk(struct kvm_mmu_page *sp,
-                           struct kvm_unsync_walk *walker)
+int mmu_pages_add(struct kvm_mmu_pages *pvec, struct kvm_mmu_page *sp,
+                   int idx)
 {
-        int i, ret;
+        int i;
 
-        if (!sp->unsync_children)
-                return 0;
+        if (sp->unsync)
+                for (i=0; i < pvec->nr; i++)
+                        if (pvec->page[i].sp == sp)
+                                return 0;
+
+        pvec->page[pvec->nr].sp = sp;
+        pvec->page[pvec->nr].idx = idx;
+        pvec->nr++;
+        return (pvec->nr == KVM_PAGE_ARRAY_NR);
+}
+
+static int __mmu_unsync_walk(struct kvm_mmu_page *sp,
+                           struct kvm_mmu_pages *pvec)
+{
+        int i, ret, nr_unsync_leaf = 0;
 
         for_each_unsync_children(sp->unsync_child_bitmap, i) {
                 u64 ent = sp->spt[i];
@@ -988,17 +1011,22 @@ static int mmu_unsync_walk(struct kvm_mmu_page *sp,
                         child = page_header(ent & PT64_BASE_ADDR_MASK);
 
                         if (child->unsync_children) {
-                                ret = mmu_unsync_walk(child, walker);
-                                if (ret)
+                                if (mmu_pages_add(pvec, child, i))
+                                        return -ENOSPC;
+
+                                ret = __mmu_unsync_walk(child, pvec);
+                                if (!ret)
+                                        __clear_bit(i, sp->unsync_child_bitmap);
+                                else if (ret > 0)
+                                        nr_unsync_leaf += ret;
+                                else
                                         return ret;
-                                __clear_bit(i, sp->unsync_child_bitmap);
                         }
 
                         if (child->unsync) {
-                                ret = walker->entry(child, walker);
-                                __clear_bit(i, sp->unsync_child_bitmap);
-                                if (ret)
-                                        return ret;
+                                nr_unsync_leaf++;
+                                if (mmu_pages_add(pvec, child, i))
+                                        return -ENOSPC;
                         }
                 }
         }
@@ -1006,7 +1034,17 @@ static int mmu_unsync_walk(struct kvm_mmu_page *sp,
         if (find_first_bit(sp->unsync_child_bitmap, 512) == 512)
                 sp->unsync_children = 0;
 
-        return 0;
+        return nr_unsync_leaf;
+}
+
+static int mmu_unsync_walk(struct kvm_mmu_page *sp,
+                           struct kvm_mmu_pages *pvec)
+{
+        if (!sp->unsync_children)
+                return 0;
+
+        mmu_pages_add(pvec, sp, 0);
+        return __mmu_unsync_walk(sp, pvec);
 }
 
 static struct kvm_mmu_page *kvm_mmu_lookup_page(struct kvm *kvm, gfn_t gfn)
@@ -1056,30 +1094,81 @@ static int kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
         return 0;
 }
 
-struct sync_walker {
-        struct kvm_vcpu *vcpu;
-        struct kvm_unsync_walk walker;
+struct mmu_page_path {
+        struct kvm_mmu_page *parent[PT64_ROOT_LEVEL-1];
+        unsigned int idx[PT64_ROOT_LEVEL-1];
 };
 
-static int mmu_sync_fn(struct kvm_mmu_page *sp, struct kvm_unsync_walk *walk)
+#define for_each_sp(pvec, sp, parents, i)                       \
+                for (i = mmu_pages_next(&pvec, &parents, -1),   \
+                        sp = pvec.page[i].sp;                   \
+                        i < pvec.nr && ({ sp = pvec.page[i].sp; 1;});   \
+                        i = mmu_pages_next(&pvec, &parents, i))
+
+int mmu_pages_next(struct kvm_mmu_pages *pvec, struct mmu_page_path *parents,
+                   int i)
 {
-        struct sync_walker *sync_walk = container_of(walk, struct sync_walker,
-                                                     walker);
-        struct kvm_vcpu *vcpu = sync_walk->vcpu;
+        int n;
+
+        for (n = i+1; n < pvec->nr; n++) {
+                struct kvm_mmu_page *sp = pvec->page[n].sp;
+
+                if (sp->role.level == PT_PAGE_TABLE_LEVEL) {
+                        parents->idx[0] = pvec->page[n].idx;
+                        return n;
+                }
 
-        kvm_sync_page(vcpu, sp);
-        return (need_resched() || spin_needbreak(&vcpu->kvm->mmu_lock));
+                parents->parent[sp->role.level-2] = sp;
+                parents->idx[sp->role.level-1] = pvec->page[n].idx;
+        }
+
+        return n;
 }
 
-static void mmu_sync_children(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
+void mmu_pages_clear_parents(struct mmu_page_path *parents)
 {
-        struct sync_walker walker = {
-                .walker = { .entry = mmu_sync_fn, },
-                .vcpu = vcpu,
-        };
+        struct kvm_mmu_page *sp;
+        unsigned int level = 0;
+
+        do {
+                unsigned int idx = parents->idx[level];
+
+                sp = parents->parent[level];
+                if (!sp)
+                        return;
+
+                --sp->unsync_children;
+                WARN_ON((int)sp->unsync_children < 0);
+                __clear_bit(idx, sp->unsync_child_bitmap);
+                level++;
+        } while (level < PT64_ROOT_LEVEL-1 && !sp->unsync_children);
+}
+
+static void kvm_mmu_pages_init(struct kvm_mmu_page *parent,
+                               struct mmu_page_path *parents,
+                               struct kvm_mmu_pages *pvec)
+{
+        parents->parent[parent->role.level-1] = NULL;
+        pvec->nr = 0;
+}
 
-        while (mmu_unsync_walk(sp, &walker.walker))
+static void mmu_sync_children(struct kvm_vcpu *vcpu,
+                              struct kvm_mmu_page *parent)
+{
+        int i;
+        struct kvm_mmu_page *sp;
+        struct mmu_page_path parents;
+        struct kvm_mmu_pages pages;
+
+        kvm_mmu_pages_init(parent, &parents, &pages);
+        while (mmu_unsync_walk(parent, &pages)) {
+                for_each_sp(pages, sp, parents, i) {
+                        kvm_sync_page(vcpu, sp);
+                        mmu_pages_clear_parents(&parents);
+                }
                 cond_resched_lock(&vcpu->kvm->mmu_lock);
+                kvm_mmu_pages_init(parent, &parents, &pages);
+        }
 }
 
 static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
@@ -1245,33 +1334,29 @@ static void kvm_mmu_unlink_parents(struct kvm *kvm, struct kvm_mmu_page *sp)
         }
 }
 
-struct zap_walker {
-        struct kvm_unsync_walk walker;
-        struct kvm *kvm;
-        int zapped;
-};
-
-static int mmu_zap_fn(struct kvm_mmu_page *sp, struct kvm_unsync_walk *walk)
-{
-        struct zap_walker *zap_walk = container_of(walk, struct zap_walker,
-                                                     walker);
-        kvm_mmu_zap_page(zap_walk->kvm, sp);
-        zap_walk->zapped = 1;
-        return 0;
-}
-
-static int mmu_zap_unsync_children(struct kvm *kvm, struct kvm_mmu_page *sp)
+static int mmu_zap_unsync_children(struct kvm *kvm,
+                                   struct kvm_mmu_page *parent)
 {
-        struct zap_walker walker = {
-                .walker = { .entry = mmu_zap_fn, },
-                .kvm = kvm,
-                .zapped = 0,
-        };
+        int i, zapped = 0;
+        struct mmu_page_path parents;
+        struct kvm_mmu_pages pages;
 
-        if (sp->role.level == PT_PAGE_TABLE_LEVEL)
+        if (parent->role.level == PT_PAGE_TABLE_LEVEL)
                 return 0;
-        mmu_unsync_walk(sp, &walker.walker);
-        return walker.zapped;
+
+        kvm_mmu_pages_init(parent, &parents, &pages);
+        while (mmu_unsync_walk(parent, &pages)) {
+                struct kvm_mmu_page *sp;
+
+                for_each_sp(pages, sp, parents, i) {
+                        kvm_mmu_zap_page(kvm, sp);
+                        mmu_pages_clear_parents(&parents);
+                }
+                zapped += pages.nr;
+                kvm_mmu_pages_init(parent, &parents, &pages);
+        }
+
+        return zapped;
 }
 
 static int kvm_mmu_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp)