forked from Minki/linux
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>
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@ -536,6 +536,8 @@ struct kvm_arch {
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* Hash table of struct kvm_mmu_page.
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*/
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struct list_head active_mmu_pages;
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struct list_head zapped_obsolete_pages;
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struct list_head assigned_dev_head;
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struct iommu_domain *iommu_domain;
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int iommu_flags;
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@ -4211,7 +4211,6 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
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static void kvm_zap_obsolete_pages(struct kvm *kvm)
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{
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struct kvm_mmu_page *sp, *node;
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LIST_HEAD(invalid_list);
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int batch = 0;
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restart:
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@ -4244,7 +4243,8 @@ restart:
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goto restart;
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}
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ret = kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
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ret = kvm_mmu_prepare_zap_page(kvm, sp,
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&kvm->arch.zapped_obsolete_pages);
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batch += ret;
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if (ret)
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@ -4255,7 +4255,7 @@ restart:
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* Should flush tlb before free page tables since lockless-walking
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* may use the pages.
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*/
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kvm_mmu_commit_zap_page(kvm, &invalid_list);
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kvm_mmu_commit_zap_page(kvm, &kvm->arch.zapped_obsolete_pages);
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}
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/*
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@ -4306,6 +4306,11 @@ restart:
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spin_unlock(&kvm->mmu_lock);
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}
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static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
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{
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return unlikely(!list_empty_careful(&kvm->arch.zapped_obsolete_pages));
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}
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static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)
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{
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struct kvm *kvm;
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@ -4334,15 +4339,23 @@ static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)
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* want to shrink a VM that only started to populate its MMU
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* anyway.
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*/
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if (!kvm->arch.n_used_mmu_pages)
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if (!kvm->arch.n_used_mmu_pages &&
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!kvm_has_zapped_obsolete_pages(kvm))
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continue;
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idx = srcu_read_lock(&kvm->srcu);
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spin_lock(&kvm->mmu_lock);
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if (kvm_has_zapped_obsolete_pages(kvm)) {
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kvm_mmu_commit_zap_page(kvm,
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&kvm->arch.zapped_obsolete_pages);
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goto unlock;
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}
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prepare_zap_oldest_mmu_page(kvm, &invalid_list);
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kvm_mmu_commit_zap_page(kvm, &invalid_list);
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unlock:
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spin_unlock(&kvm->mmu_lock);
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srcu_read_unlock(&kvm->srcu, idx);
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@ -6832,6 +6832,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
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return -EINVAL;
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INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
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INIT_LIST_HEAD(&kvm->arch.zapped_obsolete_pages);
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INIT_LIST_HEAD(&kvm->arch.assigned_dev_head);
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/* Reserve bit 0 of irq_sources_bitmap for userspace irq source */
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