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>

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ab12be4..8c2f580 100644 (file)
--- 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,