KVM: MMU: reclaim the zapped-obsolete page first
As Marcelo pointed out that
| "(retention of large number of pages while zapping)
| can be fatal, it can lead to OOM and host crash"
We introduce a list, kvm->arch.zapped_obsolete_pages, to link all
the pages which are deleted from the mmu cache but not actually
freed. When page reclaiming is needed, we always zap this kind of
pages first.
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 674c044..79af88a 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4211,7 +4211,6 @@
static void kvm_zap_obsolete_pages(struct kvm *kvm)
{
struct kvm_mmu_page *sp, *node;
- LIST_HEAD(invalid_list);
int batch = 0;
restart:
@@ -4244,7 +4243,8 @@
goto restart;
}
- ret = kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
+ ret = kvm_mmu_prepare_zap_page(kvm, sp,
+ &kvm->arch.zapped_obsolete_pages);
batch += ret;
if (ret)
@@ -4255,7 +4255,7 @@
* Should flush tlb before free page tables since lockless-walking
* may use the pages.
*/
- kvm_mmu_commit_zap_page(kvm, &invalid_list);
+ kvm_mmu_commit_zap_page(kvm, &kvm->arch.zapped_obsolete_pages);
}
/*
@@ -4306,6 +4306,11 @@
spin_unlock(&kvm->mmu_lock);
}
+static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
+{
+ return unlikely(!list_empty_careful(&kvm->arch.zapped_obsolete_pages));
+}
+
static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)
{
struct kvm *kvm;
@@ -4334,15 +4339,23 @@
* want to shrink a VM that only started to populate its MMU
* anyway.
*/
- if (!kvm->arch.n_used_mmu_pages)
+ if (!kvm->arch.n_used_mmu_pages &&
+ !kvm_has_zapped_obsolete_pages(kvm))
continue;
idx = srcu_read_lock(&kvm->srcu);
spin_lock(&kvm->mmu_lock);
+ if (kvm_has_zapped_obsolete_pages(kvm)) {
+ kvm_mmu_commit_zap_page(kvm,
+ &kvm->arch.zapped_obsolete_pages);
+ goto unlock;
+ }
+
prepare_zap_oldest_mmu_page(kvm, &invalid_list);
kvm_mmu_commit_zap_page(kvm, &invalid_list);
+unlock:
spin_unlock(&kvm->mmu_lock);
srcu_read_unlock(&kvm->srcu, idx);
