From ce00053b1cfca312c22e2a6465451f1862561eab Mon Sep 17 00:00:00 2001 From: Peter Feiner Date: Fri, 30 Jun 2017 17:26:29 -0700 Subject: [PATCH] x86: kvm: mmu: dead code thanks to access tracking The MMU always has hardware A bits or access tracking support, thus it's unnecessary to handle the scenario where we have neither. Signed-off-by: Peter Feiner Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu.c | 30 +++++++++--------------------- 1 file changed, 9 insertions(+), 21 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 5d3376f..dfd4cd6 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -315,12 +315,21 @@ static bool check_mmio_spte(struct kvm_vcpu *vcpu, u64 spte) return likely(kvm_gen == spte_gen); } +/* + * Sets the shadow PTE masks used by the MMU. + * + * Assumptions: + * - Setting either @accessed_mask or @dirty_mask requires setting both + * - At least one of @accessed_mask or @acc_track_mask must be set + */ void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask, u64 dirty_mask, u64 nx_mask, u64 x_mask, u64 p_mask, u64 acc_track_mask) { if (acc_track_mask != 0) acc_track_mask |= SPTE_SPECIAL_MASK; + BUG_ON(!dirty_mask != !accessed_mask); + BUG_ON(!accessed_mask && !acc_track_mask); shadow_user_mask = user_mask; shadow_accessed_mask = accessed_mask; @@ -1766,18 +1775,9 @@ static int kvm_test_age_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head, u64 *sptep; struct rmap_iterator iter; - /* - * If there's no access bit in the secondary pte set by the hardware and - * fast access tracking is also not enabled, it's up to gup-fast/gup to - * set the access bit in the primary pte or in the page structure. - */ - if (!shadow_accessed_mask && !shadow_acc_track_mask) - goto out; - for_each_rmap_spte(rmap_head, &iter, sptep) if (is_accessed_spte(*sptep)) return 1; -out: return 0; } @@ -1798,18 +1798,6 @@ static void rmap_recycle(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn) int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end) { - /* - * In case of absence of EPT Access and Dirty Bits supports, - * emulate the accessed bit for EPT, by checking if this page has - * an EPT mapping, and clearing it if it does. On the next access, - * a new EPT mapping will be established. - * This has some overhead, but not as much as the cost of swapping - * out actively used pages or breaking up actively used hugepages. - */ - if (!shadow_accessed_mask && !shadow_acc_track_mask) - return kvm_handle_hva_range(kvm, start, end, 0, - kvm_unmap_rmapp); - return kvm_handle_hva_range(kvm, start, end, 0, kvm_age_rmapp); } -- 2.7.4