KVM: MMU: allow the vm to shrink the kvm mmu shadow caches

Allow the Linux memory manager to reclaim memory in the kvm shadow cache.

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 56 insertions, 2 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index c563283cb982..1594ee06c920 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1966,7 +1966,53 @@ void kvm_mmu_zap_all(struct kvm *kvm)
         kvm_flush_remote_tlbs(kvm);
 }
 
-void kvm_mmu_module_exit(void)
+void kvm_mmu_remove_one_alloc_mmu_page(struct kvm *kvm)
+{
+        struct kvm_mmu_page *page;
+
+        page = container_of(kvm->arch.active_mmu_pages.prev,
+                            struct kvm_mmu_page, link);
+        kvm_mmu_zap_page(kvm, page);
+}
+
+static int mmu_shrink(int nr_to_scan, gfp_t gfp_mask)
+{
+        struct kvm *kvm;
+        struct kvm *kvm_freed = NULL;
+        int cache_count = 0;
+
+        spin_lock(&kvm_lock);
+
+        list_for_each_entry(kvm, &vm_list, vm_list) {
+                int npages;
+
+                spin_lock(&kvm->mmu_lock);
+                npages = kvm->arch.n_alloc_mmu_pages -
+                         kvm->arch.n_free_mmu_pages;
+                cache_count += npages;
+                if (!kvm_freed && nr_to_scan > 0 && npages > 0) {
+                        kvm_mmu_remove_one_alloc_mmu_page(kvm);
+                        cache_count--;
+                        kvm_freed = kvm;
+                }
+                nr_to_scan--;
+
+                spin_unlock(&kvm->mmu_lock);
+        }
+        if (kvm_freed)
+                list_move_tail(&kvm_freed->vm_list, &vm_list);
+
+        spin_unlock(&kvm_lock);
+
+        return cache_count;
+}
+
+static struct shrinker mmu_shrinker = {
+        .shrink = mmu_shrink,
+        .seeks = DEFAULT_SEEKS * 10,
+};
+
+void mmu_destroy_caches(void)
 {
         if (pte_chain_cache)
                 kmem_cache_destroy(pte_chain_cache);
@@ -1976,6 +2022,12 @@ void kvm_mmu_module_exit(void)
                 kmem_cache_destroy(mmu_page_header_cache);
 }
 
+void kvm_mmu_module_exit(void)
+{
+        mmu_destroy_caches();
+        unregister_shrinker(&mmu_shrinker);
+}
+
 int kvm_mmu_module_init(void)
 {
         pte_chain_cache = kmem_cache_create("kvm_pte_chain",
@@ -1995,10 +2047,12 @@ int kvm_mmu_module_init(void)
         if (!mmu_page_header_cache)
                 goto nomem;
 
+        register_shrinker(&mmu_shrinker);
+
         return 0;
 
 nomem:
-        kvm_mmu_module_exit();
+        mmu_destroy_caches();
         return -ENOMEM;
 }