From: Sean Christopherson Date: Wed, 8 Jan 2020 20:24:46 +0000 (-0800) Subject: KVM: x86/mmu: Fold max_mapping_level() into kvm_mmu_hugepage_adjust() X-Git-Tag: v5.15~4592^2~8 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=293e306e7faac4eafaefb9518a1cd6eaecad88e9;p=platform%2Fkernel%2Flinux-starfive.git KVM: x86/mmu: Fold max_mapping_level() into kvm_mmu_hugepage_adjust() Fold max_mapping_level() into kvm_mmu_hugepage_adjust() now that HugeTLB mappings are handled in kvm_mmu_hugepage_adjust(), i.e. there isn't a need to pre-calculate the max mapping level. Co-locating all hugepage checks eliminates a memslot lookup, at the cost of performing the __mmu_gfn_lpage_is_disallowed() checks while holding mmu_lock. The latency of lpage_is_disallowed() is likely negligible relative to the rest of the code run while holding mmu_lock, and can be offset to some extent by eliminating the mmu_gfn_lpage_is_disallowed() check in set_spte() in a future patch. Eliminating the check in set_spte() is made possible by performing the initial lpage_is_disallowed() checks while holding mmu_lock. Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini --- diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 9090842..812c69f 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -1310,27 +1310,6 @@ gfn_to_memslot_dirty_bitmap(struct kvm_vcpu *vcpu, gfn_t gfn, return slot; } -static int max_mapping_level(struct kvm_vcpu *vcpu, gfn_t gfn, - int max_level) -{ - struct kvm_memory_slot *slot; - - if (unlikely(max_level == PT_PAGE_TABLE_LEVEL)) - return PT_PAGE_TABLE_LEVEL; - - slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn); - if (!memslot_valid_for_gpte(slot, true)) - return PT_PAGE_TABLE_LEVEL; - - max_level = min(max_level, kvm_x86_ops->get_lpage_level()); - for ( ; max_level > PT_PAGE_TABLE_LEVEL; max_level--) { - if (!__mmu_gfn_lpage_is_disallowed(gfn, max_level, slot)) - break; - } - - return max_level; -} - /* * About rmap_head encoding: * @@ -3101,10 +3080,11 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, if (pte_access & ACC_WRITE_MASK) { /* - * Other vcpu creates new sp in the window between - * max_mapping_level() and acquiring mmu-lock. We can - * allow guest to retry the access, the mapping can - * be fixed if guest refault. + * Legacy code to handle an obsolete scenario where a different + * vcpu creates new sp in the window between this vcpu's query + * of lpage_is_disallowed() and acquiring mmu_lock. No longer + * necessary now that lpage_is_disallowed() is called after + * acquiring mmu_lock. */ if (level > PT_PAGE_TABLE_LEVEL && mmu_gfn_lpage_is_disallowed(vcpu, gfn, level)) @@ -3295,9 +3275,8 @@ static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep) } static int host_pfn_mapping_level(struct kvm_vcpu *vcpu, gfn_t gfn, - kvm_pfn_t pfn) + kvm_pfn_t pfn, struct kvm_memory_slot *slot) { - struct kvm_memory_slot *slot; unsigned long hva; pte_t *pte; int level; @@ -3309,10 +3288,14 @@ static int host_pfn_mapping_level(struct kvm_vcpu *vcpu, gfn_t gfn, if (!PageCompound(pfn_to_page(pfn))) return PT_PAGE_TABLE_LEVEL; - slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, true); - if (!slot) - return PT_PAGE_TABLE_LEVEL; - + /* + * Note, using the already-retrieved memslot and __gfn_to_hva_memslot() + * is not solely for performance, it's also necessary to avoid the + * "writable" check in __gfn_to_hva_many(), which will always fail on + * read-only memslots due to gfn_to_hva() assuming writes. Earlier + * page fault steps have already verified the guest isn't writing a + * read-only memslot. + */ hva = __gfn_to_hva_memslot(slot, gfn); pte = lookup_address_in_mm(vcpu->kvm->mm, hva, &level); @@ -3325,18 +3308,32 @@ static int host_pfn_mapping_level(struct kvm_vcpu *vcpu, gfn_t gfn, static int kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, gfn_t gfn, int max_level, kvm_pfn_t *pfnp) { + struct kvm_memory_slot *slot; kvm_pfn_t pfn = *pfnp; kvm_pfn_t mask; int level; - if (max_level == PT_PAGE_TABLE_LEVEL) + 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)) return PT_PAGE_TABLE_LEVEL; - level = host_pfn_mapping_level(vcpu, gfn, pfn); + slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, true); + if (!slot) + return PT_PAGE_TABLE_LEVEL; + + max_level = min(max_level, kvm_x86_ops->get_lpage_level()); + for ( ; max_level > PT_PAGE_TABLE_LEVEL; max_level--) { + if (!__mmu_gfn_lpage_is_disallowed(gfn, max_level, slot)) + break; + } + + if (max_level == PT_PAGE_TABLE_LEVEL) + return PT_PAGE_TABLE_LEVEL; + + level = host_pfn_mapping_level(vcpu, gfn, pfn, slot); if (level == PT_PAGE_TABLE_LEVEL) return level; @@ -4177,8 +4174,6 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code, if (lpage_disallowed) max_level = PT_PAGE_TABLE_LEVEL; - max_level = max_mapping_level(vcpu, gfn, max_level); - if (fast_page_fault(vcpu, gpa, error_code)) return RET_PF_RETRY; diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h index 885da92..4e1ef04 100644 --- a/arch/x86/kvm/mmu/paging_tmpl.h +++ b/arch/x86/kvm/mmu/paging_tmpl.h @@ -832,8 +832,6 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gpa_t addr, u32 error_code, else max_level = walker.level; - max_level = max_mapping_level(vcpu, walker.gfn, max_level); - mmu_seq = vcpu->kvm->mmu_notifier_seq; smp_rmb();