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 return xchg(rcu_dereference(sptep), new_spte); 25 } 26 27 static inline void __kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 new_spte) 28 { 29 WRITE_ONCE(*rcu_dereference(sptep), new_spte); 30 } 31 32 /* 33 * SPTEs must be modified atomically if they are shadow-present, leaf 34 * SPTEs, and have volatile bits, i.e. has bits that can be set outside 35 * of mmu_lock. The Writable bit can be set by KVM's fast page fault 36 * handler, and Accessed and Dirty bits can be set by the CPU. 37 * 38 * Note, non-leaf SPTEs do have Accessed bits and those bits are 39 * technically volatile, but KVM doesn't consume the Accessed bit of 40 * non-leaf SPTEs, i.e. KVM doesn't care if it clobbers the bit. This 41 * logic needs to be reassessed if KVM were to use non-leaf Accessed 42 * bits, e.g. to skip stepping down into child SPTEs when aging SPTEs. 43 */ 44 static inline bool kvm_tdp_mmu_spte_need_atomic_write(u64 old_spte, int level) 45 { 46 return is_shadow_present_pte(old_spte) && 47 is_last_spte(old_spte, level) && 48 spte_has_volatile_bits(old_spte); 49 } 50 51 static inline u64 kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 old_spte, 52 u64 new_spte, int level) 53 { 54 if (kvm_tdp_mmu_spte_need_atomic_write(old_spte, level)) 55 return kvm_tdp_mmu_write_spte_atomic(sptep, new_spte); 56 57 __kvm_tdp_mmu_write_spte(sptep, new_spte); 58 return old_spte; 59 } 60 61 static inline u64 tdp_mmu_clear_spte_bits(tdp_ptep_t sptep, u64 old_spte, 62 u64 mask, int level) 63 { 64 atomic64_t *sptep_atomic; 65 66 if (kvm_tdp_mmu_spte_need_atomic_write(old_spte, level)) { 67 sptep_atomic = (atomic64_t *)rcu_dereference(sptep); 68 return (u64)atomic64_fetch_and(~mask, sptep_atomic); 69 } 70 71 __kvm_tdp_mmu_write_spte(sptep, old_spte & ~mask); 72 return old_spte; 73 } 74 75 /* 76 * A TDP iterator performs a pre-order walk over a TDP paging structure. 77 */ 78 struct tdp_iter { 79 /* 80 * The iterator will traverse the paging structure towards the mapping 81 * for this GFN. 82 */ 83 gfn_t next_last_level_gfn; 84 /* 85 * The next_last_level_gfn at the time when the thread last 86 * yielded. Only yielding when the next_last_level_gfn != 87 * yielded_gfn helps ensure forward progress. 88 */ 89 gfn_t yielded_gfn; 90 /* Pointers to the page tables traversed to reach the current SPTE */ 91 tdp_ptep_t pt_path[PT64_ROOT_MAX_LEVEL]; 92 /* A pointer to the current SPTE */ 93 tdp_ptep_t sptep; 94 /* The lowest GFN mapped by the current SPTE */ 95 gfn_t gfn; 96 /* The level of the root page given to the iterator */ 97 int root_level; 98 /* The lowest level the iterator should traverse to */ 99 int min_level; 100 /* The iterator's current level within the paging structure */ 101 int level; 102 /* The address space ID, i.e. SMM vs. regular. */ 103 int as_id; 104 /* A snapshot of the value at sptep */ 105 u64 old_spte; 106 /* 107 * Whether the iterator has a valid state. This will be false if the 108 * iterator walks off the end of the paging structure. 109 */ 110 bool valid; 111 /* 112 * True if KVM dropped mmu_lock and yielded in the middle of a walk, in 113 * which case tdp_iter_next() needs to restart the walk at the root 114 * level instead of advancing to the next entry. 115 */ 116 bool yielded; 117 }; 118 119 /* 120 * Iterates over every SPTE mapping the GFN range [start, end) in a 121 * preorder traversal. 122 */ 123 #define for_each_tdp_pte_min_level(iter, root, min_level, start, end) \ 124 for (tdp_iter_start(&iter, root, min_level, start); \ 125 iter.valid && iter.gfn < end; \ 126 tdp_iter_next(&iter)) 127 128 #define for_each_tdp_pte(iter, root, start, end) \ 129 for_each_tdp_pte_min_level(iter, root, PG_LEVEL_4K, start, end) 130 131 tdp_ptep_t spte_to_child_pt(u64 pte, int level); 132 133 void tdp_iter_start(struct tdp_iter *iter, struct kvm_mmu_page *root, 134 int min_level, gfn_t next_last_level_gfn); 135 void tdp_iter_next(struct tdp_iter *iter); 136 void tdp_iter_restart(struct tdp_iter *iter); 137 138 #endif /* __KVM_X86_MMU_TDP_ITER_H */ 139