[RFC,16/16,v6] allow user to dump a fraction of the memory

diff --git a/dump.c b/dump.c
index 6322d1a..60a5180 100644
--- a/dump.c
+++ b/dump.c
@@ -77,6 +77,9 @@  typedef struct DumpState {
     char *error;
     int fd;
     bool detach;
+    bool has_filter;
+    int64_t begin;
+    int64_t length;
     target_phys_addr_t memory_offset;
     int64_t bandwidth;
     RAMBlock *block;
@@ -397,23 +400,82 @@  static int write_memory(DumpState *s, RAMBlock *block, ram_addr_t start,
 
 /* get the memory's offset in the vmcore */
 static target_phys_addr_t get_offset(target_phys_addr_t phys_addr,
-                                     target_phys_addr_t memory_offset)
+                                     DumpState *s)
 {
     RAMBlock *block;
-    target_phys_addr_t offset = memory_offset;
+    target_phys_addr_t offset = s->memory_offset;
+    int64_t size_in_block, start;
+
+    if (s->has_filter) {
+        if (phys_addr < s->begin || phys_addr >= s->begin + s->length) {
+            return -1;
+        }
+    }
 
     QLIST_FOREACH(block, &ram_list.blocks, next) {
-        if (phys_addr >= block->offset &&
-            phys_addr < block->offset + block->length) {
-            return phys_addr - block->offset + offset;
+        if (s->has_filter) {
+            if (block->offset >= s->begin + s->length ||
+                block->offset + block->length <= s->begin) {
+                /* This block is out of the range */
+                continue;
+            }
+
+            if (s->begin <= block->offset) {
+                start = block->offset;
+            } else {
+                start = s->begin;
+            }
+
+            size_in_block = block->length - (start - block->offset);
+            if (s->begin + s->length < block->offset + block->length) {
+                size_in_block -= block->offset + block->length -
+                                 (s->begin + s->length);
+            }
+        } else {
+            start = block->offset;
+            size_in_block = block->length;
         }
-        offset += block->length;
+
+        if (phys_addr >= start && phys_addr < start + size_in_block) {
+            return phys_addr - start + offset;
+        }
+
+        offset += size_in_block;
     }
 
     return -1;
 }
 
-static DumpState *dump_init(int fd, bool detach, Error **errp)
+static ram_addr_t get_start_block(DumpState *s)
+{
+    RAMBlock *block;
+
+    if (!s->has_filter) {
+        s->block = QLIST_FIRST(&ram_list.blocks);
+        return 0;
+    }
+
+    QLIST_FOREACH(block, &ram_list.blocks, next) {
+        if (block->offset >= s->begin + s->length ||
+            block->offset + block->length <= s->begin) {
+            /* This block is out of the range */
+            continue;
+        }
+
+        s->block = block;
+        if (s->begin > block->offset ) {
+            s->start = s->begin - block->offset;
+        } else {
+            s->start = 0;
+        }
+        return s->start;
+    }
+
+    return -1;
+}
+
+static DumpState *dump_init(int fd, bool detach, bool has_filter, int64_t begin,
+                            int64_t length, Error **errp)
 {
     CPUState *env;
     DumpState *s = dump_get_current();
@@ -427,10 +489,17 @@  static DumpState *dump_init(int fd, bool detach, Error **errp)
         s->error = NULL;
     }
     s->fd = fd;
-    s->block = QLIST_FIRST(&ram_list.blocks);
-    s->start = 0;
     s->timer = NULL;
     s->detach = detach;
+    s->has_filter = has_filter;
+    s->begin = begin;
+    s->length = length;
+
+    s->start = get_start_block(s);
+    if (s->start == -1) {
+        error_set(errp, QERR_INVALID_PARAMETER, "begin");
+        return NULL;
+    }
 
     /*
      * get dump info: endian, class and architecture.
@@ -454,6 +523,10 @@  static DumpState *dump_init(int fd, bool detach, Error **errp)
     QTAILQ_INIT(&s->list.head);
     get_memory_mapping(&s->list);
 
+    if (s->has_filter) {
+        filter_memory_mapping(&s->list, s->begin, s->length);
+    }
+
     /* crash needs extra memory mapping to determine phys_base. */
     ret = cpu_add_extra_memory_mapping(&s->list);
     if (ret < 0) {
@@ -547,7 +620,7 @@  static int dump_completed(DumpState *s)
     int phdr_index = 1, ret;
 
     QTAILQ_FOREACH(memory_mapping, &s->list.head, next) {
-        offset = get_offset(memory_mapping->phys_addr, s->memory_offset);
+        offset = get_offset(memory_mapping->phys_addr, s);
         if (s->dump_info.d_class == ELFCLASS64) {
             ret = write_elf64_load(s, memory_mapping, phdr_index++, offset);
         } else {
@@ -563,6 +636,33 @@  static int dump_completed(DumpState *s)
     return 0;
 }
 
+static int get_next_block(DumpState *s, RAMBlock *block)
+{
+    while (1) {
+        block = QLIST_NEXT(block, next);
+        if (!block) {
+            /* no more block */
+            return 1;
+        }
+
+        s->start = 0;
+        s->block = block;
+        if (s->has_filter) {
+            if (block->offset >= s->begin + s->length ||
+                block->offset + block->length <= s->begin) {
+                /* This block is out of the range */
+                continue;
+            }
+
+            if (s->begin > block->offset) {
+                s->start = s->begin - block->offset;
+            }
+        }
+
+        return 0;
+    }
+}
+
 /*
  * write memory to vmcore.
  *
@@ -573,47 +673,39 @@  static int dump_completed(DumpState *s)
  */
 static int dump_iterate(DumpState *s, int64_t deadline)
 {
-    RAMBlock *block = s->block;
+    RAMBlock *block;
     target_phys_addr_t offset = s->offset;
-    int64_t size, remain, writen_size;
+    int64_t size, writen_size, size_in_block;
     int64_t total = s->bandwidth / 10;
     int ret;
+    bool first = true;
 
-    if ((block->length - s->start) >= total) {
-        size = total;
-    } else {
-        size = block->length - s->start;
-    }
-
-    ret = write_memory(s, block, s->start, &offset, &size, deadline);
-    if (ret < 0) {
-        return -1;
-    }
-
-    if (size == total || ret == 1) {
-        if ((size + s->start) == block->length) {
-            s->block = QLIST_NEXT(block, next);
-            s->start = 0;
+    size = 0;
+    while (size < total) {
+        if (first) {
+            first = false;
         } else {
-            s->start += size;
+            ret = get_next_block(s, block);
+            if (ret == 1) {
+                /* we have finished */
+                return 1;
+            }
         }
-        goto end;
-    }
 
-    while (size < total) {
-        block = QLIST_NEXT(block, next);
-        if (!block) {
-            /* we have finished */
-            return 1;
+        block = s->block;
+        writen_size = total - size;
+        size_in_block = block->length - s->start;
+        if (s->has_filter &&
+            s->begin + s->length < block->offset + block->length) {
+            size_in_block -= block->offset + block->length -
+                             (s->begin + s->length);
         }
 
-        remain = total - size;
-        if (remain >= block->length) {
-            writen_size = block->length;
-        } else {
-            writen_size = remain;
+        if (writen_size >= size_in_block) {
+            writen_size = size_in_block;
         }
-        ret = write_memory(s, block, 0, &offset, &writen_size, deadline);
+
+        ret = write_memory(s, block, s->start, &offset, &writen_size, deadline);
         if (ret < 0) {
             return -1;
         } else if (ret == 1) {
@@ -621,21 +713,17 @@  static int dump_iterate(DumpState *s, int64_t deadline)
         }
         size += writen_size;
     }
-    if (writen_size == block->length) {
-        s->block = QLIST_NEXT(block, next);
-        s->start = 0;
+    if (writen_size == size_in_block) {
+        ret = get_next_block(s, block);
+        if (ret == 1) {
+            /* we have finished */
+            return 1;
+        }
     } else {
-        s->block = block;
-        s->start = writen_size;
+        s->start += writen_size;
     }
 
-end:
     s->offset = offset;
-    if (!s->block) {
-        /* we have finished */
-        return 1;
-    }
-
     return 0;
 }
 
@@ -687,12 +775,22 @@  static void dump_vm_state_change(void *opaque, int running, RunState state)
     }
 }
 
-void qmp_dump(bool detach, const char *file, Error **errp)
+void qmp_dump(bool detach, const char *file, bool has_begin, int64_t begin,
+              bool has_length, int64_t length, Error **errp)
 {
     const char *p;
     int fd = -1;
     DumpState *s;
 
+    if (has_begin && !has_length) {
+        error_set(errp, QERR_MISSING_PARAMETER, "length");
+        return;
+    }
+    if (!has_begin && has_length) {
+        error_set(errp, QERR_MISSING_PARAMETER, "begin");
+        return;
+    }
+
 #if !defined(WIN32)
     if (strstart(file, "fd:", &p)) {
         fd = qemu_get_fd(p);
@@ -716,7 +814,7 @@  void qmp_dump(bool detach, const char *file, Error **errp)
         return;
     }
 
-    s = dump_init(fd, detach, errp);
+    s = dump_init(fd, detach, has_begin, begin, length, errp);
     if (!s) {
         return;
     }
diff --git a/hmp-commands.hx b/hmp-commands.hx
index a026905..388b9ac 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -868,9 +868,11 @@  ETEXI
 
     {
         .name       = "dump",
-        .args_type  = "detach:-d,file:s",
+        .args_type  = "detach:-d,file:s,begin:i?,length:i?",
         .params     = "file",
-        .help       = "dump to file (using -d to not wait for completion)",
+        .help       = "dump to file (using -d to not wait for completion)"
+                      "\n\t\t\t begin(optional): the starting physical address"
+                      "\n\t\t\t length(optional): the memory size, in bytes",
         .user_print = monitor_user_noop,
         .mhandler.cmd = hmp_dump,
     },
diff --git a/hmp.c b/hmp.c
index b36921c..e0c5c62 100644
--- a/hmp.c
+++ b/hmp.c
@@ -857,8 +857,19 @@  void hmp_dump(Monitor *mon, const QDict *qdict)
     Error *errp = NULL;
     bool detach = qdict_get_try_bool(qdict, "detach", 0);
     const char *file = qdict_get_str(qdict, "file");
+    bool has_begin = qdict_haskey(qdict, "begin");
+    bool has_length = qdict_haskey(qdict, "length");
+    int64_t begin = 0;
+    int64_t length = 0;
 
-    qmp_dump(detach, file, &errp);
+    if (has_begin) {
+        begin = qdict_get_int(qdict, "begin");
+    }
+    if (has_length) {
+        length = qdict_get_int(qdict, "length");
+    }
+
+    qmp_dump(detach, file, has_begin, begin, has_length, length, &errp);
     hmp_handle_error(mon, &errp);
 }
 
diff --git a/memory_mapping.c b/memory_mapping.c
index fc0ddee..e2fcf2e 100644
--- a/memory_mapping.c
+++ b/memory_mapping.c
@@ -193,3 +193,30 @@  void get_memory_mapping(MemoryMappingList *list)
 
     return;
 }
+
+void filter_memory_mapping(MemoryMappingList *list, int64_t begin,
+                           int64_t length)
+{
+    MemoryMapping *cur, *next;
+
+    QTAILQ_FOREACH_SAFE(cur, &list->head, next, next) {
+        if (cur->phys_addr >= begin + length ||
+            cur->phys_addr + cur->length <= begin) {
+            QTAILQ_REMOVE(&list->head, cur, next);
+            list->num--;
+            continue;
+        }
+
+        if (cur->phys_addr < begin) {
+            cur->length -= begin - cur->phys_addr;
+            if (cur->virt_addr) {
+                cur->virt_addr += begin - cur->phys_addr;
+            }
+            cur->phys_addr = begin;
+        }
+
+        if (cur->phys_addr + cur->length > begin + length) {
+            cur->length -= cur->phys_addr + cur->length - begin - length;
+        }
+    }
+}
diff --git a/memory_mapping.h b/memory_mapping.h
index 679f9ef..c7bb4fa 100644
--- a/memory_mapping.h
+++ b/memory_mapping.h
@@ -35,5 +35,7 @@  void add_to_memory_mapping(MemoryMappingList *list,
 
 void free_memory_mapping_list(MemoryMappingList *list);
 void get_memory_mapping(MemoryMappingList *list);
+void filter_memory_mapping(MemoryMappingList *list, int64_t begin,
+                           int64_t length);
 
 #endif
diff --git a/qapi-schema.json b/qapi-schema.json
index 27d5199..aee9efa 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1590,12 +1590,16 @@ 
 #
 # @detach: detached dumping.
 # @file: the filename or file descriptor of the vmcore.
+# @begin: if specified, the starting physical address.
+# @length: if specified, the memory size, in bytes.
 #
 # Returns: nothing on success
 #
 # Since: 1.1
 ##
-{ 'command': 'dump', 'data': { 'detach': 'bool', 'file': 'str' } }
+{ 'command': 'dump',
+  'data': { 'detach': 'bool', 'file': 'str', '*begin': 'int',
+            '*length': 'int' } }
 
 ##
 # @dump_cancel
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 1656eea..0c72536 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -567,7 +567,7 @@  EQMP
 
     {
         .name       = "dump",
-        .args_type  = "detach:-d,file:s",
+        .args_type  = "detach:-d,file:s,begin:i?,end:i?",
         .params     = "file",
         .help       = "dump to file (using -d to not wait for completion)",
         .user_print = monitor_user_noop,
@@ -584,6 +584,8 @@  Arguments:
 
 - "detach": detached dumping (json-bool, optional)
 - "file":   Destination file (json-string)
+- "begin":  the starting physical address (json-int)
+- "length": the memory size, in bytes (json-int)
 
 Example: