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Commit 365c8868 authored by Xiao Guangrong's avatar Xiao Guangrong Committed by Gleb Natapov
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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: default avatarXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
parent f34d251d

arch/x86/include/asm/kvm_host.h

+2 −0
Original line number Diff line number Diff line
@@ -536,6 +536,8 @@ struct kvm_arch { 
	 * Hash table of struct kvm_mmu_page.

	 */

	struct list_head active_mmu_pages;

	struct list_head zapped_obsolete_pages;



	struct list_head assigned_dev_head;

	struct iommu_domain *iommu_domain;

	int iommu_flags;

arch/x86/kvm/mmu.c

+17 −4
Original line number Diff line number Diff line
@@ -4211,7 +4211,6 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot) 
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 @@ static void kvm_zap_obsolete_pages(struct kvm *kvm) 
			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 @@ static void kvm_zap_obsolete_pages(struct kvm *kvm) 
	 * 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 @@ void kvm_mmu_zap_mmio_sptes(struct kvm *kvm) 
	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 @@ static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc) 
		 * 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);

arch/x86/kvm/x86.c

+1 −0
Original line number Diff line number Diff line
@@ -6832,6 +6832,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) 
		return -EINVAL;



	INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);

	INIT_LIST_HEAD(&kvm->arch.zapped_obsolete_pages);

	INIT_LIST_HEAD(&kvm->arch.assigned_dev_head);



	/* Reserve bit 0 of irq_sources_bitmap for userspace irq source */