KVM: MMU: don't walk every parent pages while mark unsync

While we mark the parent's unsync_child_bitmap, if the parent is already
unsynced, it no need walk it's parent, it can reduce some unnecessary
workload

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 17 insertions, 44 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ab12be4eb105..8c2f580956d9 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -175,7 +175,7 @@ struct kvm_shadow_walk_iterator {
              shadow_walk_okay(&(_walker));                      \
              shadow_walk_next(&(_walker)))
 
-typedef int (*mmu_parent_walk_fn) (struct kvm_mmu_page *sp);
+typedef void (*mmu_parent_walk_fn) (struct kvm_mmu_page *sp, u64 *spte);
 
 static struct kmem_cache *pte_chain_cache;
 static struct kmem_cache *rmap_desc_cache;
@@ -1024,7 +1024,6 @@ static void mmu_page_remove_parent_pte(struct kvm_mmu_page *sp,
         BUG();
 }
 
-
 static void mmu_parent_walk(struct kvm_mmu_page *sp, mmu_parent_walk_fn fn)
 {
         struct kvm_pte_chain *pte_chain;
@@ -1034,63 +1033,37 @@ static void mmu_parent_walk(struct kvm_mmu_page *sp, mmu_parent_walk_fn fn)
 
         if (!sp->multimapped && sp->parent_pte) {
                 parent_sp = page_header(__pa(sp->parent_pte));
-                fn(parent_sp);
-                mmu_parent_walk(parent_sp, fn);
+                fn(parent_sp, sp->parent_pte);
                 return;
         }
+
         hlist_for_each_entry(pte_chain, node, &sp->parent_ptes, link)
                 for (i = 0; i < NR_PTE_CHAIN_ENTRIES; ++i) {
-                        if (!pte_chain->parent_ptes[i])
+                        u64 *spte = pte_chain->parent_ptes[i];
+
+                        if (!spte)
                                 break;
-                        parent_sp = page_header(__pa(pte_chain->parent_ptes[i]));
-                        fn(parent_sp);
-                        mmu_parent_walk(parent_sp, fn);
+                        parent_sp = page_header(__pa(spte));
+                        fn(parent_sp, spte);
                 }
 }
 
-static void kvm_mmu_update_unsync_bitmap(u64 *spte)
+static void mark_unsync(struct kvm_mmu_page *sp, u64 *spte);
+static void kvm_mmu_mark_parents_unsync(struct kvm_mmu_page *sp)
 {
-        unsigned int index;
-        struct kvm_mmu_page *sp = page_header(__pa(spte));
-
-        index = spte - sp->spt;
-        if (!__test_and_set_bit(index, sp->unsync_child_bitmap))
-                sp->unsync_children++;
-        WARN_ON(!sp->unsync_children);
+        mmu_parent_walk(sp, mark_unsync);
 }
 
-static void kvm_mmu_update_parents_unsync(struct kvm_mmu_page *sp)
+static void mark_unsync(struct kvm_mmu_page *sp, u64 *spte)
 {
-        struct kvm_pte_chain *pte_chain;
-        struct hlist_node *node;
-        int i;
+        unsigned int index;
 
-        if (!sp->parent_pte)
+        index = spte - sp->spt;
+        if (__test_and_set_bit(index, sp->unsync_child_bitmap))
                 return;
-
-        if (!sp->multimapped) {
-                kvm_mmu_update_unsync_bitmap(sp->parent_pte);
+        if (sp->unsync_children++)
                 return;
-        }
-
-        hlist_for_each_entry(pte_chain, node, &sp->parent_ptes, link)
-                for (i = 0; i < NR_PTE_CHAIN_ENTRIES; ++i) {
-                        if (!pte_chain->parent_ptes[i])
-                                break;
-                        kvm_mmu_update_unsync_bitmap(pte_chain->parent_ptes[i]);
-                }
-}
-
-static int unsync_walk_fn(struct kvm_mmu_page *sp)
-{
-        kvm_mmu_update_parents_unsync(sp);
-        return 1;
-}
-
-static void kvm_mmu_mark_parents_unsync(struct kvm_mmu_page *sp)
-{
-        mmu_parent_walk(sp, unsync_walk_fn);
-        kvm_mmu_update_parents_unsync(sp);
+        kvm_mmu_mark_parents_unsync(sp);
 }
 
 static void nonpaging_prefetch_page(struct kvm_vcpu *vcpu,