1 // SPDX-License-Identifier: GPL-2.0 2 3 #ifndef __KVM_X86_MMU_TDP_ITER_H 4 #define __KVM_X86_MMU_TDP_ITER_H 5 6 #include <linux/kvm_host.h> 7 8 #include "mmu.h" 9 #include "spte.h" 10 11 /* 12 * TDP MMU SPTEs are RCU protected to allow paging structures (non-leaf SPTEs) 13 * to be zapped while holding mmu_lock for read, and to allow TLB flushes to be 14 * batched without having to collect the list of zapped SPs. Flows that can 15 * remove SPs must service pending TLB flushes prior to dropping RCU protection. 16 */ 17 static inline u64 kvm_tdp_mmu_read_spte(tdp_ptep_t sptep) 18 { 19 return READ_ONCE(*rcu_dereference(sptep)); 20 } 21 22 static inline u64 kvm_tdp_mmu_write_spte_atomic(tdp_ptep_t sptep, u64 new_spte) 23 { 24 KVM_MMU_WARN_ON(is_ept_ve_possible(new_spte)); 25 return xchg(rcu_dereference(sptep), new_spte); 26 } 27 28 static inline void __kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 new_spte) 29 { 30 KVM_MMU_WARN_ON(is_ept_ve_possible(new_spte)); 31 WRITE_ONCE(*rcu_dereference(sptep), new_spte); 32 } 33 34 /* 35 * SPTEs must be modified atomically if they are shadow-present, leaf 36 * SPTEs, and have volatile bits, i.e. has bits that can be set outside 37 * of mmu_lock. The Writable bit can be set by KVM's fast page fault 38 * handler, and Accessed and Dirty bits can be set by the CPU. 39 * 40 * Note, non-leaf SPTEs do have Accessed bits and those bits are 41 * technically volatile, but KVM doesn't consume the Accessed bit of 42 * non-leaf SPTEs, i.e. KVM doesn't care if it clobbers the bit. This 43 * logic needs to be reassessed if KVM were to use non-leaf Accessed 44 * bits, e.g. to skip stepping down into child SPTEs when aging SPTEs. 45 */ 46 static inline bool kvm_tdp_mmu_spte_need_atomic_write(u64 old_spte, int level) 47 { 48 return is_shadow_present_pte(old_spte) && 49 is_last_spte(old_spte, level) && 50 spte_has_volatile_bits(old_spte); 51 } 52 53 static inline u64 kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 old_spte, 54 u64 new_spte, int level) 55 { 56 if (kvm_tdp_mmu_spte_need_atomic_write(old_spte, level)) 57 return kvm_tdp_mmu_write_spte_atomic(sptep, new_spte); 58 59 __kvm_tdp_mmu_write_spte(sptep, new_spte); 60 return old_spte; 61 } 62 63 static inline u64 tdp_mmu_clear_spte_bits(tdp_ptep_t sptep, u64 old_spte, 64 u64 mask, int level) 65 { 66 atomic64_t *sptep_atomic; 67 68 if (kvm_tdp_mmu_spte_need_atomic_write(old_spte, level)) { 69 sptep_atomic = (atomic64_t *)rcu_dereference(sptep); 70 return (u64)atomic64_fetch_and(~mask, sptep_atomic); 71 } 72 73 __kvm_tdp_mmu_write_spte(sptep, old_spte & ~mask); 74 return old_spte; 75 } 76 77 /* 78 * A TDP iterator performs a pre-order walk over a TDP paging structure. 79 */ 80 struct tdp_iter { 81 /* 82 * The iterator will traverse the paging structure towards the mapping 83 * for this GFN. 84 */ 85 gfn_t next_last_level_gfn; 86 /* 87 * The next_last_level_gfn at the time when the thread last 88 * yielded. Only yielding when the next_last_level_gfn != 89 * yielded_gfn helps ensure forward progress. 90 */ 91 gfn_t yielded_gfn; 92 /* Pointers to the page tables traversed to reach the current SPTE */ 93 tdp_ptep_t pt_path[PT64_ROOT_MAX_LEVEL]; 94 /* A pointer to the current SPTE */ 95 tdp_ptep_t sptep; 96 /* The lowest GFN mapped by the current SPTE */ 97 gfn_t gfn; 98 /* The level of the root page given to the iterator */ 99 int root_level; 100 /* The lowest level the iterator should traverse to */ 101 int min_level; 102 /* The iterator's current level within the paging structure */ 103 int level; 104 /* The address space ID, i.e. SMM vs. regular. */ 105 int as_id; 106 /* A snapshot of the value at sptep */ 107 u64 old_spte; 108 /* 109 * Whether the iterator has a valid state. This will be false if the 110 * iterator walks off the end of the paging structure. 111 */ 112 bool valid; 113 /* 114 * True if KVM dropped mmu_lock and yielded in the middle of a walk, in 115 * which case tdp_iter_next() needs to restart the walk at the root 116 * level instead of advancing to the next entry. 117 */ 118 bool yielded; 119 }; 120 121 /* 122 * Iterates over every SPTE mapping the GFN range [start, end) in a 123 * preorder traversal. 124 */ 125 #define for_each_tdp_pte_min_level(iter, root, min_level, start, end) \ 126 for (tdp_iter_start(&iter, root, min_level, start); \ 127 iter.valid && iter.gfn < end; \ 128 tdp_iter_next(&iter)) 129 130 #define for_each_tdp_pte(iter, root, start, end) \ 131 for_each_tdp_pte_min_level(iter, root, PG_LEVEL_4K, start, end) 132 133 tdp_ptep_t spte_to_child_pt(u64 pte, int level); 134 135 void tdp_iter_start(struct tdp_iter *iter, struct kvm_mmu_page *root, 136 int min_level, gfn_t next_last_level_gfn); 137 void tdp_iter_next(struct tdp_iter *iter); 138 void tdp_iter_restart(struct tdp_iter *iter); 139 140 #endif /* __KVM_X86_MMU_TDP_ITER_H */ 141