1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * VMware VMCI Driver 4 * 5 * Copyright (C) 2012 VMware, Inc. All rights reserved. 6 */ 7 8 #include <linux/vmw_vmci_defs.h> 9 #include <linux/hash.h> 10 #include <linux/types.h> 11 #include <linux/rculist.h> 12 #include <linux/completion.h> 13 14 #include "vmci_resource.h" 15 #include "vmci_driver.h" 16 17 18 #define VMCI_RESOURCE_HASH_BITS 7 19 #define VMCI_RESOURCE_HASH_BUCKETS (1 << VMCI_RESOURCE_HASH_BITS) 20 21 struct vmci_hash_table { 22 spinlock_t lock; 23 struct hlist_head entries[VMCI_RESOURCE_HASH_BUCKETS]; 24 }; 25 26 static struct vmci_hash_table vmci_resource_table = { 27 .lock = __SPIN_LOCK_UNLOCKED(vmci_resource_table.lock), 28 }; 29 30 static unsigned int vmci_resource_hash(struct vmci_handle handle) 31 { 32 return hash_32(handle.resource, VMCI_RESOURCE_HASH_BITS); 33 } 34 35 /* 36 * Gets a resource (if one exists) matching given handle from the hash table. 37 */ 38 static struct vmci_resource *vmci_resource_lookup(struct vmci_handle handle, 39 enum vmci_resource_type type) 40 { 41 struct vmci_resource *r, *resource = NULL; 42 unsigned int idx = vmci_resource_hash(handle); 43 44 rcu_read_lock(); 45 hlist_for_each_entry_rcu(r, 46 &vmci_resource_table.entries[idx], node) { 47 u32 cid = r->handle.context; 48 u32 rid = r->handle.resource; 49 50 if (r->type == type && 51 rid == handle.resource && 52 (cid == handle.context || cid == VMCI_INVALID_ID || 53 handle.context == VMCI_INVALID_ID)) { 54 resource = r; 55 break; 56 } 57 } 58 rcu_read_unlock(); 59 60 return resource; 61 } 62 63 /* 64 * Find an unused resource ID and return it. The first 65 * VMCI_RESERVED_RESOURCE_ID_MAX are reserved so we start from 66 * its value + 1. 67 * Returns VMCI resource id on success, VMCI_INVALID_ID on failure. 68 */ 69 static u32 vmci_resource_find_id(u32 context_id, 70 enum vmci_resource_type resource_type) 71 { 72 static u32 resource_id = VMCI_RESERVED_RESOURCE_ID_MAX + 1; 73 u32 old_rid = resource_id; 74 u32 current_rid; 75 76 /* 77 * Generate a unique resource ID. Keep on trying until we wrap around 78 * in the RID space. 79 */ 80 do { 81 struct vmci_handle handle; 82 83 current_rid = resource_id; 84 resource_id++; 85 if (unlikely(resource_id == VMCI_INVALID_ID)) { 86 /* Skip the reserved rids. */ 87 resource_id = VMCI_RESERVED_RESOURCE_ID_MAX + 1; 88 } 89 90 handle = vmci_make_handle(context_id, current_rid); 91 if (!vmci_resource_lookup(handle, resource_type)) 92 return current_rid; 93 } while (resource_id != old_rid); 94 95 return VMCI_INVALID_ID; 96 } 97 98 99 int vmci_resource_add(struct vmci_resource *resource, 100 enum vmci_resource_type resource_type, 101 struct vmci_handle handle) 102 103 { 104 unsigned int idx; 105 int result; 106 107 spin_lock(&vmci_resource_table.lock); 108 109 if (handle.resource == VMCI_INVALID_ID) { 110 handle.resource = vmci_resource_find_id(handle.context, 111 resource_type); 112 if (handle.resource == VMCI_INVALID_ID) { 113 result = VMCI_ERROR_NO_HANDLE; 114 goto out; 115 } 116 } else if (vmci_resource_lookup(handle, resource_type)) { 117 result = VMCI_ERROR_ALREADY_EXISTS; 118 goto out; 119 } 120 121 resource->handle = handle; 122 resource->type = resource_type; 123 INIT_HLIST_NODE(&resource->node); 124 kref_init(&resource->kref); 125 init_completion(&resource->done); 126 127 idx = vmci_resource_hash(resource->handle); 128 hlist_add_head_rcu(&resource->node, &vmci_resource_table.entries[idx]); 129 130 result = VMCI_SUCCESS; 131 132 out: 133 spin_unlock(&vmci_resource_table.lock); 134 return result; 135 } 136 137 void vmci_resource_remove(struct vmci_resource *resource) 138 { 139 struct vmci_handle handle = resource->handle; 140 unsigned int idx = vmci_resource_hash(handle); 141 struct vmci_resource *r; 142 143 /* Remove resource from hash table. */ 144 spin_lock(&vmci_resource_table.lock); 145 146 hlist_for_each_entry(r, &vmci_resource_table.entries[idx], node) { 147 if (vmci_handle_is_equal(r->handle, resource->handle)) { 148 hlist_del_init_rcu(&r->node); 149 break; 150 } 151 } 152 153 spin_unlock(&vmci_resource_table.lock); 154 synchronize_rcu(); 155 156 vmci_resource_put(resource); 157 wait_for_completion(&resource->done); 158 } 159 160 struct vmci_resource * 161 vmci_resource_by_handle(struct vmci_handle resource_handle, 162 enum vmci_resource_type resource_type) 163 { 164 struct vmci_resource *r, *resource = NULL; 165 166 rcu_read_lock(); 167 168 r = vmci_resource_lookup(resource_handle, resource_type); 169 if (r && 170 (resource_type == r->type || 171 resource_type == VMCI_RESOURCE_TYPE_ANY)) { 172 resource = vmci_resource_get(r); 173 } 174 175 rcu_read_unlock(); 176 177 return resource; 178 } 179 180 /* 181 * Get a reference to given resource. 182 */ 183 struct vmci_resource *vmci_resource_get(struct vmci_resource *resource) 184 { 185 kref_get(&resource->kref); 186 187 return resource; 188 } 189 190 static void vmci_release_resource(struct kref *kref) 191 { 192 struct vmci_resource *resource = 193 container_of(kref, struct vmci_resource, kref); 194 195 /* Verify the resource has been unlinked from hash table */ 196 WARN_ON(!hlist_unhashed(&resource->node)); 197 198 /* Signal that container of this resource can now be destroyed */ 199 complete(&resource->done); 200 } 201 202 /* 203 * Resource's release function will get called if last reference. 204 * If it is the last reference, then we are sure that nobody else 205 * can increment the count again (it's gone from the resource hash 206 * table), so there's no need for locking here. 207 */ 208 int vmci_resource_put(struct vmci_resource *resource) 209 { 210 /* 211 * We propagate the information back to caller in case it wants to know 212 * whether entry was freed. 213 */ 214 return kref_put(&resource->kref, vmci_release_resource) ? 215 VMCI_SUCCESS_ENTRY_DEAD : VMCI_SUCCESS; 216 } 217 218 struct vmci_handle vmci_resource_handle(struct vmci_resource *resource) 219 { 220 return resource->handle; 221 } 222