xref: /openbmc/qemu/block/qed.h (revision 1f051dcb)
1 /*
2  * QEMU Enhanced Disk Format
3  *
4  * Copyright IBM, Corp. 2010
5  *
6  * Authors:
7  *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>
8  *  Anthony Liguori   <aliguori@us.ibm.com>
9  *
10  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
11  * See the COPYING.LIB file in the top-level directory.
12  *
13  */
14 
15 #ifndef BLOCK_QED_H
16 #define BLOCK_QED_H
17 
18 #include "block/block_int.h"
19 #include "qemu/cutils.h"
20 
21 /* The layout of a QED file is as follows:
22  *
23  * +--------+----------+----------+----------+-----+
24  * | header | L1 table | cluster0 | cluster1 | ... |
25  * +--------+----------+----------+----------+-----+
26  *
27  * There is a 2-level pagetable for cluster allocation:
28  *
29  *                     +----------+
30  *                     | L1 table |
31  *                     +----------+
32  *                ,------'  |  '------.
33  *           +----------+   |    +----------+
34  *           | L2 table |  ...   | L2 table |
35  *           +----------+        +----------+
36  *       ,------'  |  '------.
37  *  +----------+   |    +----------+
38  *  |   Data   |  ...   |   Data   |
39  *  +----------+        +----------+
40  *
41  * The L1 table is fixed size and always present.  L2 tables are allocated on
42  * demand.  The L1 table size determines the maximum possible image size; it
43  * can be influenced using the cluster_size and table_size values.
44  *
45  * All fields are little-endian on disk.
46  */
47 #define  QED_DEFAULT_CLUSTER_SIZE  65536
48 enum {
49     QED_MAGIC = 'Q' | 'E' << 8 | 'D' << 16 | '\0' << 24,
50 
51     /* The image supports a backing file */
52     QED_F_BACKING_FILE = 0x01,
53 
54     /* The image needs a consistency check before use */
55     QED_F_NEED_CHECK = 0x02,
56 
57     /* The backing file format must not be probed, treat as raw image */
58     QED_F_BACKING_FORMAT_NO_PROBE = 0x04,
59 
60     /* Feature bits must be used when the on-disk format changes */
61     QED_FEATURE_MASK = QED_F_BACKING_FILE | /* supported feature bits */
62                        QED_F_NEED_CHECK |
63                        QED_F_BACKING_FORMAT_NO_PROBE,
64     QED_COMPAT_FEATURE_MASK = 0,            /* supported compat feature bits */
65     QED_AUTOCLEAR_FEATURE_MASK = 0,         /* supported autoclear feature bits */
66 
67     /* Data is stored in groups of sectors called clusters.  Cluster size must
68      * be large to avoid keeping too much metadata.  I/O requests that have
69      * sub-cluster size will require read-modify-write.
70      */
71     QED_MIN_CLUSTER_SIZE = 4 * 1024, /* in bytes */
72     QED_MAX_CLUSTER_SIZE = 64 * 1024 * 1024,
73 
74     /* Allocated clusters are tracked using a 2-level pagetable.  Table size is
75      * a multiple of clusters so large maximum image sizes can be supported
76      * without jacking up the cluster size too much.
77      */
78     QED_MIN_TABLE_SIZE = 1,        /* in clusters */
79     QED_MAX_TABLE_SIZE = 16,
80     QED_DEFAULT_TABLE_SIZE = 4,
81 
82     /* Delay to flush and clean image after last allocating write completes */
83     QED_NEED_CHECK_TIMEOUT = 5,    /* in seconds */
84 };
85 
86 typedef struct {
87     uint32_t magic;                 /* QED\0 */
88 
89     uint32_t cluster_size;          /* in bytes */
90     uint32_t table_size;            /* for L1 and L2 tables, in clusters */
91     uint32_t header_size;           /* in clusters */
92 
93     uint64_t features;              /* format feature bits */
94     uint64_t compat_features;       /* compatible feature bits */
95     uint64_t autoclear_features;    /* self-resetting feature bits */
96 
97     uint64_t l1_table_offset;       /* in bytes */
98     uint64_t image_size;            /* total logical image size, in bytes */
99 
100     /* if (features & QED_F_BACKING_FILE) */
101     uint32_t backing_filename_offset; /* in bytes from start of header */
102     uint32_t backing_filename_size;   /* in bytes */
103 } QEMU_PACKED QEDHeader;
104 
105 typedef struct {
106     uint64_t offsets[0];            /* in bytes */
107 } QEDTable;
108 
109 /* The L2 cache is a simple write-through cache for L2 structures */
110 typedef struct CachedL2Table {
111     QEDTable *table;
112     uint64_t offset;    /* offset=0 indicates an invalidate entry */
113     QTAILQ_ENTRY(CachedL2Table) node;
114     int ref;
115 } CachedL2Table;
116 
117 typedef struct {
118     QTAILQ_HEAD(, CachedL2Table) entries;
119     unsigned int n_entries;
120 } L2TableCache;
121 
122 typedef struct QEDRequest {
123     CachedL2Table *l2_table;
124 } QEDRequest;
125 
126 enum {
127     QED_AIOCB_WRITE = 0x0001,       /* read or write? */
128     QED_AIOCB_ZERO  = 0x0002,       /* zero write, used with QED_AIOCB_WRITE */
129 };
130 
131 typedef struct QEDAIOCB {
132     BlockDriverState *bs;
133     QSIMPLEQ_ENTRY(QEDAIOCB) next;  /* next request */
134     int flags;                      /* QED_AIOCB_* bits ORed together */
135     uint64_t end_pos;               /* request end on block device, in bytes */
136 
137     /* User scatter-gather list */
138     QEMUIOVector *qiov;
139     size_t qiov_offset;             /* byte count already processed */
140 
141     /* Current cluster scatter-gather list */
142     QEMUIOVector cur_qiov;
143     uint64_t cur_pos;               /* position on block device, in bytes */
144     uint64_t cur_cluster;           /* cluster offset in image file */
145     unsigned int cur_nclusters;     /* number of clusters being accessed */
146     int find_cluster_ret;           /* used for L1/L2 update */
147 
148     QEDRequest request;
149 } QEDAIOCB;
150 
151 typedef struct {
152     BlockDriverState *bs;           /* device */
153 
154     /* Written only by an allocating write or the timer handler (the latter
155      * while allocating reqs are plugged).
156      */
157     QEDHeader header;               /* always cpu-endian */
158 
159     /* Protected by table_lock.  */
160     CoMutex table_lock;
161     QEDTable *l1_table;
162     L2TableCache l2_cache;          /* l2 table cache */
163     uint32_t table_nelems;
164     uint32_t l1_shift;
165     uint32_t l2_shift;
166     uint32_t l2_mask;
167     uint64_t file_size;             /* length of image file, in bytes */
168 
169     /* Allocating write request queue */
170     QEDAIOCB *allocating_acb;
171     CoQueue allocating_write_reqs;
172     bool allocating_write_reqs_plugged;
173 
174     /* Periodic flush and clear need check flag */
175     QEMUTimer *need_check_timer;
176 } BDRVQEDState;
177 
178 enum {
179     QED_CLUSTER_FOUND,         /* cluster found */
180     QED_CLUSTER_ZERO,          /* zero cluster found */
181     QED_CLUSTER_L2,            /* cluster missing in L2 */
182     QED_CLUSTER_L1,            /* cluster missing in L1 */
183 };
184 
185 /**
186  * Header functions
187  */
188 int GRAPH_RDLOCK qed_write_header_sync(BDRVQEDState *s);
189 
190 /**
191  * L2 cache functions
192  */
193 void qed_init_l2_cache(L2TableCache *l2_cache);
194 void qed_free_l2_cache(L2TableCache *l2_cache);
195 CachedL2Table *qed_alloc_l2_cache_entry(L2TableCache *l2_cache);
196 void qed_unref_l2_cache_entry(CachedL2Table *entry);
197 CachedL2Table *qed_find_l2_cache_entry(L2TableCache *l2_cache, uint64_t offset);
198 void qed_commit_l2_cache_entry(L2TableCache *l2_cache, CachedL2Table *l2_table);
199 
200 /**
201  * Table I/O functions
202  */
203 int coroutine_fn GRAPH_RDLOCK qed_read_l1_table_sync(BDRVQEDState *s);
204 
205 int coroutine_fn GRAPH_RDLOCK
206 qed_write_l1_table(BDRVQEDState *s, unsigned int index, unsigned int n);
207 
208 int coroutine_fn GRAPH_RDLOCK
209 qed_write_l1_table_sync(BDRVQEDState *s, unsigned int index, unsigned int n);
210 
211 int coroutine_fn GRAPH_RDLOCK
212 qed_read_l2_table_sync(BDRVQEDState *s, QEDRequest *request, uint64_t offset);
213 
214 int coroutine_fn GRAPH_RDLOCK
215 qed_read_l2_table(BDRVQEDState *s, QEDRequest *request, uint64_t offset);
216 
217 int coroutine_fn GRAPH_RDLOCK
218 qed_write_l2_table(BDRVQEDState *s, QEDRequest *request, unsigned int index,
219                    unsigned int n, bool flush);
220 
221 int coroutine_fn GRAPH_RDLOCK
222 qed_write_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
223                         unsigned int index, unsigned int n, bool flush);
224 
225 /**
226  * Cluster functions
227  */
228 int coroutine_fn GRAPH_RDLOCK
229 qed_find_cluster(BDRVQEDState *s, QEDRequest *request, uint64_t pos,
230                  size_t *len, uint64_t *img_offset);
231 
232 /**
233  * Consistency check
234  */
235 int coroutine_fn GRAPH_RDLOCK
236 qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix);
237 
238 QEDTable *qed_alloc_table(BDRVQEDState *s);
239 
240 /**
241  * Round down to the start of a cluster
242  */
qed_start_of_cluster(BDRVQEDState * s,uint64_t offset)243 static inline uint64_t qed_start_of_cluster(BDRVQEDState *s, uint64_t offset)
244 {
245     return offset & ~(uint64_t)(s->header.cluster_size - 1);
246 }
247 
qed_offset_into_cluster(BDRVQEDState * s,uint64_t offset)248 static inline uint64_t qed_offset_into_cluster(BDRVQEDState *s, uint64_t offset)
249 {
250     return offset & (s->header.cluster_size - 1);
251 }
252 
qed_bytes_to_clusters(BDRVQEDState * s,uint64_t bytes)253 static inline uint64_t qed_bytes_to_clusters(BDRVQEDState *s, uint64_t bytes)
254 {
255     return qed_start_of_cluster(s, bytes + (s->header.cluster_size - 1)) /
256            (s->header.cluster_size - 1);
257 }
258 
qed_l1_index(BDRVQEDState * s,uint64_t pos)259 static inline unsigned int qed_l1_index(BDRVQEDState *s, uint64_t pos)
260 {
261     return pos >> s->l1_shift;
262 }
263 
qed_l2_index(BDRVQEDState * s,uint64_t pos)264 static inline unsigned int qed_l2_index(BDRVQEDState *s, uint64_t pos)
265 {
266     return (pos >> s->l2_shift) & s->l2_mask;
267 }
268 
269 /**
270  * Test if a cluster offset is valid
271  */
qed_check_cluster_offset(BDRVQEDState * s,uint64_t offset)272 static inline bool qed_check_cluster_offset(BDRVQEDState *s, uint64_t offset)
273 {
274     uint64_t header_size = (uint64_t)s->header.header_size *
275                            s->header.cluster_size;
276 
277     if (offset & (s->header.cluster_size - 1)) {
278         return false;
279     }
280     return offset >= header_size && offset < s->file_size;
281 }
282 
283 /**
284  * Test if a table offset is valid
285  */
qed_check_table_offset(BDRVQEDState * s,uint64_t offset)286 static inline bool qed_check_table_offset(BDRVQEDState *s, uint64_t offset)
287 {
288     uint64_t end_offset = offset + (s->header.table_size - 1) *
289                           s->header.cluster_size;
290 
291     /* Overflow check */
292     if (end_offset <= offset) {
293         return false;
294     }
295 
296     return qed_check_cluster_offset(s, offset) &&
297            qed_check_cluster_offset(s, end_offset);
298 }
299 
qed_offset_is_cluster_aligned(BDRVQEDState * s,uint64_t offset)300 static inline bool qed_offset_is_cluster_aligned(BDRVQEDState *s,
301                                                  uint64_t offset)
302 {
303     if (qed_offset_into_cluster(s, offset)) {
304         return false;
305     }
306     return true;
307 }
308 
qed_offset_is_unalloc_cluster(uint64_t offset)309 static inline bool qed_offset_is_unalloc_cluster(uint64_t offset)
310 {
311     if (offset == 0) {
312         return true;
313     }
314     return false;
315 }
316 
qed_offset_is_zero_cluster(uint64_t offset)317 static inline bool qed_offset_is_zero_cluster(uint64_t offset)
318 {
319     if (offset == 1) {
320         return true;
321     }
322     return false;
323 }
324 
325 #endif /* BLOCK_QED_H */
326