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KVM: x86/mmu: Use huge pages for DAX-backed files
Walk the host page tables to identify hugepage mappings for ZONE_DEVICE pfns, i.e. DAX pages. Explicitly query kvm_is_zone_device_pfn() when deciding whether or not to bother walking the host page tables, as DAX pages do not set up the head/tail infrastructure, i.e. will return false for PageCompound() even when using huge pages. Zap ZONE_DEVICE sptes when disabling dirty logging, e.g. if live migration fails, to allow KVM to rebuild large pages for DAX-based mappings. Presumably DAX favors large pages, and worst case scenario is a minor performance hit as KVM will need to re-fault all DAX-based pages. Suggested-by: Barret Rhoden <brho@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Jason Zeng <jason.zeng@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Liran Alon <liran.alon@oracle.com> Cc: linux-nvdimm <linux-nvdimm@lists.01.org> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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1 changed files with 4 additions and 5 deletions
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@ -3250,7 +3250,7 @@ static int host_pfn_mapping_level(struct kvm_vcpu *vcpu, gfn_t gfn,
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PT_DIRECTORY_LEVEL != (int)PG_LEVEL_2M ||
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PT_PDPE_LEVEL != (int)PG_LEVEL_1G);
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if (!PageCompound(pfn_to_page(pfn)))
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if (!PageCompound(pfn_to_page(pfn)) && !kvm_is_zone_device_pfn(pfn))
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return PT_PAGE_TABLE_LEVEL;
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/*
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@ -3282,8 +3282,7 @@ static int kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, gfn_t gfn,
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if (unlikely(max_level == PT_PAGE_TABLE_LEVEL))
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return PT_PAGE_TABLE_LEVEL;
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if (is_error_noslot_pfn(pfn) || kvm_is_reserved_pfn(pfn) ||
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kvm_is_zone_device_pfn(pfn))
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if (is_error_noslot_pfn(pfn) || kvm_is_reserved_pfn(pfn))
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return PT_PAGE_TABLE_LEVEL;
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slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, true);
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@ -5912,8 +5911,8 @@ static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
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* mapping if the indirect sp has level = 1.
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*/
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if (sp->role.direct && !kvm_is_reserved_pfn(pfn) &&
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!kvm_is_zone_device_pfn(pfn) &&
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PageCompound(pfn_to_page(pfn))) {
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(kvm_is_zone_device_pfn(pfn) ||
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PageCompound(pfn_to_page(pfn)))) {
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pte_list_remove(rmap_head, sptep);
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if (kvm_available_flush_tlb_with_range())
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