KVM: MMU: Introduce a helper function for FIFO zapping

Make the code for zapping the oldest mmu page, placed at the tail of the
active list, a separate function.

Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 23 insertions, 32 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 0f42645a063c..fdacabba6f62 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2110,6 +2110,21 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,
         }
 }
 
+static bool prepare_zap_oldest_mmu_page(struct kvm *kvm,
+                                        struct list_head *invalid_list)
+{
+        struct kvm_mmu_page *sp;
+
+        if (list_empty(&kvm->arch.active_mmu_pages))
+                return false;
+
+        sp = list_entry(kvm->arch.active_mmu_pages.prev,
+                        struct kvm_mmu_page, link);
+        kvm_mmu_prepare_zap_page(kvm, sp, invalid_list);
+
+        return true;
+}
+
 /*
  * Changing the number of mmu pages allocated to the vm
  * Note: if goal_nr_mmu_pages is too small, you will get dead lock
@@ -2117,23 +2132,15 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,
 void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int goal_nr_mmu_pages)
 {
         LIST_HEAD(invalid_list);
-        /*
-         * If we set the number of mmu pages to be smaller be than the
-         * number of actived pages , we must to free some mmu pages before we
-         * change the value
-         */
 
         spin_lock(&kvm->mmu_lock);
 
         if (kvm->arch.n_used_mmu_pages > goal_nr_mmu_pages) {
-                while (kvm->arch.n_used_mmu_pages > goal_nr_mmu_pages &&
-                        !list_empty(&kvm->arch.active_mmu_pages)) {
-                        struct kvm_mmu_page *page;
+                /* Need to free some mmu pages to achieve the goal. */
+                while (kvm->arch.n_used_mmu_pages > goal_nr_mmu_pages)
+                        if (!prepare_zap_oldest_mmu_page(kvm, &invalid_list))
+                                break;
 
-                        page = container_of(kvm->arch.active_mmu_pages.prev,
-                                            struct kvm_mmu_page, link);
-                        kvm_mmu_prepare_zap_page(kvm, page, &invalid_list);
-                }
                 kvm_mmu_commit_zap_page(kvm, &invalid_list);
                 goal_nr_mmu_pages = kvm->arch.n_used_mmu_pages;
         }
@@ -4007,13 +4014,10 @@ void __kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu)
 {
         LIST_HEAD(invalid_list);
 
-        while (kvm_mmu_available_pages(vcpu->kvm) < KVM_REFILL_PAGES &&
-               !list_empty(&vcpu->kvm->arch.active_mmu_pages)) {
-                struct kvm_mmu_page *sp;
+        while (kvm_mmu_available_pages(vcpu->kvm) < KVM_REFILL_PAGES) {
+                if (!prepare_zap_oldest_mmu_page(vcpu->kvm, &invalid_list))
+                        break;
 
-                sp = container_of(vcpu->kvm->arch.active_mmu_pages.prev,
-                                  struct kvm_mmu_page, link);
-                kvm_mmu_prepare_zap_page(vcpu->kvm, sp, &invalid_list);
                 ++vcpu->kvm->stat.mmu_recycled;
         }
         kvm_mmu_commit_zap_page(vcpu->kvm, &invalid_list);
@@ -4182,19 +4186,6 @@ restart:
         spin_unlock(&kvm->mmu_lock);
 }
 
-static void kvm_mmu_remove_some_alloc_mmu_pages(struct kvm *kvm,
-                                                struct list_head *invalid_list)
-{
-        struct kvm_mmu_page *page;
-
-        if (list_empty(&kvm->arch.active_mmu_pages))
-                return;
-
-        page = container_of(kvm->arch.active_mmu_pages.prev,
-                            struct kvm_mmu_page, link);
-        kvm_mmu_prepare_zap_page(kvm, page, invalid_list);
-}
-
 static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)
 {
         struct kvm *kvm;
@@ -4229,7 +4220,7 @@ static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)
                 idx = srcu_read_lock(&kvm->srcu);
                 spin_lock(&kvm->mmu_lock);
 
-                kvm_mmu_remove_some_alloc_mmu_pages(kvm, &invalid_list);
+                prepare_zap_oldest_mmu_page(kvm, &invalid_list);
                 kvm_mmu_commit_zap_page(kvm, &invalid_list);
 
                 spin_unlock(&kvm->mmu_lock);