From dcadda146f4fd25a732382747f306465d337cda6 Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Tue, 30 Aug 2016 17:05:55 +0100 Subject: arm/kvm: excise redundant cache maintenance When modifying Stage-2 page tables, we perform cache maintenance to account for non-coherent page table walks. However, this is unnecessary, as page table walks are guaranteed to be coherent in the presence of the virtualization extensions. Per ARM DDI 0406C.c, section B1.7 ("The Virtualization Extensions"), the virtualization extensions mandate the multiprocessing extensions. Per ARM DDI 0406C.c, section B3.10.1 ("General TLB maintenance requirements"), as described in the sub-section titled "TLB maintenance operations and the memory order model", this maintenance is not required in the presence of the multiprocessing extensions. Hence, we need not perform this cache maintenance when modifying Stage-2 entries. This patch removes the logic for performing the redundant maintenance. To ensure visibility and ordering of updates, a dsb(ishst) that was otherwise implicit in the maintenance is folded into kvm_set_pmd() and kvm_set_pte(). Signed-off-by: Mark Rutland Cc: Christoffer Dall Cc: Marc Zyngier Cc: kvmarm@lists.cs.columbia.edu Signed-off-by: Christoffer Dall --- arch/arm/include/asm/kvm_mmu.h | 28 ++-------------------------- arch/arm/kvm/mmu.c | 2 -- 2 files changed, 2 insertions(+), 28 deletions(-) diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h index 3bb803d6814b..74a44727f8e1 100644 --- a/arch/arm/include/asm/kvm_mmu.h +++ b/arch/arm/include/asm/kvm_mmu.h @@ -63,37 +63,13 @@ void kvm_clear_hyp_idmap(void); static inline void kvm_set_pmd(pmd_t *pmd, pmd_t new_pmd) { *pmd = new_pmd; - flush_pmd_entry(pmd); + dsb(ishst); } static inline void kvm_set_pte(pte_t *pte, pte_t new_pte) { *pte = new_pte; - /* - * flush_pmd_entry just takes a void pointer and cleans the necessary - * cache entries, so we can reuse the function for ptes. - */ - flush_pmd_entry(pte); -} - -static inline void kvm_clean_pgd(pgd_t *pgd) -{ - clean_dcache_area(pgd, PTRS_PER_S2_PGD * sizeof(pgd_t)); -} - -static inline void kvm_clean_pmd(pmd_t *pmd) -{ - clean_dcache_area(pmd, PTRS_PER_PMD * sizeof(pmd_t)); -} - -static inline void kvm_clean_pmd_entry(pmd_t *pmd) -{ - clean_pmd_entry(pmd); -} - -static inline void kvm_clean_pte(pte_t *pte) -{ - clean_pte_table(pte); + dsb(ishst); } static inline pte_t kvm_s2pte_mkwrite(pte_t pte) diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c index 29d0b23af2a9..344755dcc3b2 100644 --- a/arch/arm/kvm/mmu.c +++ b/arch/arm/kvm/mmu.c @@ -744,7 +744,6 @@ int kvm_alloc_stage2_pgd(struct kvm *kvm) if (!pgd) return -ENOMEM; - kvm_clean_pgd(pgd); kvm->arch.pgd = pgd; return 0; } @@ -936,7 +935,6 @@ static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache, if (!cache) return 0; /* ignore calls from kvm_set_spte_hva */ pte = mmu_memory_cache_alloc(cache); - kvm_clean_pte(pte); pmd_populate_kernel(NULL, pmd, pte); get_page(virt_to_page(pmd)); } -- cgit