From e851265a816f96a86c5a0316d2fc4d45be76d1d4 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 8 Jan 2020 12:24:48 -0800 Subject: [PATCH] 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 Cc: David Hildenbrand Cc: Dan Williams Cc: Jason Zeng Cc: Dave Jiang Cc: Liran Alon Cc: linux-nvdimm Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu/mmu.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index a9e6683c802b..febd65a9721a 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3250,7 +3250,7 @@ static int host_pfn_mapping_level(struct kvm_vcpu *vcpu, gfn_t gfn, PT_DIRECTORY_LEVEL != (int)PG_LEVEL_2M || PT_PDPE_LEVEL != (int)PG_LEVEL_1G); - if (!PageCompound(pfn_to_page(pfn))) + if (!PageCompound(pfn_to_page(pfn)) && !kvm_is_zone_device_pfn(pfn)) return PT_PAGE_TABLE_LEVEL; /* @@ -3282,8 +3282,7 @@ static int kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, gfn_t gfn, if (unlikely(max_level == PT_PAGE_TABLE_LEVEL)) return PT_PAGE_TABLE_LEVEL; - if (is_error_noslot_pfn(pfn) || kvm_is_reserved_pfn(pfn) || - kvm_is_zone_device_pfn(pfn)) + if (is_error_noslot_pfn(pfn) || kvm_is_reserved_pfn(pfn)) return PT_PAGE_TABLE_LEVEL; slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, true); @@ -5912,8 +5911,8 @@ static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm, * mapping if the indirect sp has level = 1. */ if (sp->role.direct && !kvm_is_reserved_pfn(pfn) && - !kvm_is_zone_device_pfn(pfn) && - PageCompound(pfn_to_page(pfn))) { + (kvm_is_zone_device_pfn(pfn) || + PageCompound(pfn_to_page(pfn)))) { pte_list_remove(rmap_head, sptep); if (kvm_available_flush_tlb_with_range())