1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* 3 * KVM dirty ring implementation 4 * 5 * Copyright 2019 Red Hat, Inc. 6 */ 7 #include <linux/kvm_host.h> 8 #include <linux/kvm.h> 9 #include <linux/vmalloc.h> 10 #include <linux/kvm_dirty_ring.h> 11 #include <trace/events/kvm.h> 12 #include "mmu_lock.h" 13 14 int __weak kvm_cpu_dirty_log_size(void) 15 { 16 return 0; 17 } 18 19 u32 kvm_dirty_ring_get_rsvd_entries(void) 20 { 21 return KVM_DIRTY_RING_RSVD_ENTRIES + kvm_cpu_dirty_log_size(); 22 } 23 24 static u32 kvm_dirty_ring_used(struct kvm_dirty_ring *ring) 25 { 26 return READ_ONCE(ring->dirty_index) - READ_ONCE(ring->reset_index); 27 } 28 29 bool kvm_dirty_ring_soft_full(struct kvm_dirty_ring *ring) 30 { 31 return kvm_dirty_ring_used(ring) >= ring->soft_limit; 32 } 33 34 static bool kvm_dirty_ring_full(struct kvm_dirty_ring *ring) 35 { 36 return kvm_dirty_ring_used(ring) >= ring->size; 37 } 38 39 struct kvm_dirty_ring *kvm_dirty_ring_get(struct kvm *kvm) 40 { 41 struct kvm_vcpu *vcpu = kvm_get_running_vcpu(); 42 43 WARN_ON_ONCE(vcpu->kvm != kvm); 44 45 return &vcpu->dirty_ring; 46 } 47 48 static void kvm_reset_dirty_gfn(struct kvm *kvm, u32 slot, u64 offset, u64 mask) 49 { 50 struct kvm_memory_slot *memslot; 51 int as_id, id; 52 53 as_id = slot >> 16; 54 id = (u16)slot; 55 56 if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS) 57 return; 58 59 memslot = id_to_memslot(__kvm_memslots(kvm, as_id), id); 60 61 if (!memslot || (offset + __fls(mask)) >= memslot->npages) 62 return; 63 64 KVM_MMU_LOCK(kvm); 65 kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot, offset, mask); 66 KVM_MMU_UNLOCK(kvm); 67 } 68 69 int kvm_dirty_ring_alloc(struct kvm_dirty_ring *ring, int index, u32 size) 70 { 71 ring->dirty_gfns = vzalloc(size); 72 if (!ring->dirty_gfns) 73 return -ENOMEM; 74 75 ring->size = size / sizeof(struct kvm_dirty_gfn); 76 ring->soft_limit = ring->size - kvm_dirty_ring_get_rsvd_entries(); 77 ring->dirty_index = 0; 78 ring->reset_index = 0; 79 ring->index = index; 80 81 return 0; 82 } 83 84 static inline void kvm_dirty_gfn_set_invalid(struct kvm_dirty_gfn *gfn) 85 { 86 gfn->flags = 0; 87 } 88 89 static inline void kvm_dirty_gfn_set_dirtied(struct kvm_dirty_gfn *gfn) 90 { 91 gfn->flags = KVM_DIRTY_GFN_F_DIRTY; 92 } 93 94 static inline bool kvm_dirty_gfn_harvested(struct kvm_dirty_gfn *gfn) 95 { 96 return gfn->flags & KVM_DIRTY_GFN_F_RESET; 97 } 98 99 int kvm_dirty_ring_reset(struct kvm *kvm, struct kvm_dirty_ring *ring) 100 { 101 u32 cur_slot, next_slot; 102 u64 cur_offset, next_offset; 103 unsigned long mask; 104 int count = 0; 105 struct kvm_dirty_gfn *entry; 106 bool first_round = true; 107 108 /* This is only needed to make compilers happy */ 109 cur_slot = cur_offset = mask = 0; 110 111 while (true) { 112 entry = &ring->dirty_gfns[ring->reset_index & (ring->size - 1)]; 113 114 if (!kvm_dirty_gfn_harvested(entry)) 115 break; 116 117 next_slot = READ_ONCE(entry->slot); 118 next_offset = READ_ONCE(entry->offset); 119 120 /* Update the flags to reflect that this GFN is reset */ 121 kvm_dirty_gfn_set_invalid(entry); 122 123 ring->reset_index++; 124 count++; 125 /* 126 * Try to coalesce the reset operations when the guest is 127 * scanning pages in the same slot. 128 */ 129 if (!first_round && next_slot == cur_slot) { 130 s64 delta = next_offset - cur_offset; 131 132 if (delta >= 0 && delta < BITS_PER_LONG) { 133 mask |= 1ull << delta; 134 continue; 135 } 136 137 /* Backwards visit, careful about overflows! */ 138 if (delta > -BITS_PER_LONG && delta < 0 && 139 (mask << -delta >> -delta) == mask) { 140 cur_offset = next_offset; 141 mask = (mask << -delta) | 1; 142 continue; 143 } 144 } 145 kvm_reset_dirty_gfn(kvm, cur_slot, cur_offset, mask); 146 cur_slot = next_slot; 147 cur_offset = next_offset; 148 mask = 1; 149 first_round = false; 150 } 151 152 kvm_reset_dirty_gfn(kvm, cur_slot, cur_offset, mask); 153 154 trace_kvm_dirty_ring_reset(ring); 155 156 return count; 157 } 158 159 void kvm_dirty_ring_push(struct kvm_dirty_ring *ring, u32 slot, u64 offset) 160 { 161 struct kvm_dirty_gfn *entry; 162 163 /* It should never get full */ 164 WARN_ON_ONCE(kvm_dirty_ring_full(ring)); 165 166 entry = &ring->dirty_gfns[ring->dirty_index & (ring->size - 1)]; 167 168 entry->slot = slot; 169 entry->offset = offset; 170 /* 171 * Make sure the data is filled in before we publish this to 172 * the userspace program. There's no paired kernel-side reader. 173 */ 174 smp_wmb(); 175 kvm_dirty_gfn_set_dirtied(entry); 176 ring->dirty_index++; 177 trace_kvm_dirty_ring_push(ring, slot, offset); 178 } 179 180 struct page *kvm_dirty_ring_get_page(struct kvm_dirty_ring *ring, u32 offset) 181 { 182 return vmalloc_to_page((void *)ring->dirty_gfns + offset * PAGE_SIZE); 183 } 184 185 void kvm_dirty_ring_free(struct kvm_dirty_ring *ring) 186 { 187 vfree(ring->dirty_gfns); 188 ring->dirty_gfns = NULL; 189 } 190