[Qemu-devel] [5434] Introduce v3 of savevm protocol

[Anthony Liguori]

Revision: 5434
          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=5434
Author:   aliguori
Date:     2008-10-06 14:53:52 +0000 (Mon, 06 Oct 2008)

Log Message:
-----------
Introduce v3 of savevm protocol

The current savevm/loadvm protocol has some draw backs.  It does not support
the ability to do progressive saving which means it cannot be used for live
checkpointing or migration.  The sections sizes are 32-bit integers which
means that it will not function when using more than 4GB of memory for a guest.
It attempts to seek within the output file which means it cannot be streamed.
The current protocol also is pretty lax about how it supports forward
compatibility.  If a saved section version is greater than what the restore
code support, the restore code generally treats the saved data as being in
whatever version it supports.  This means that restoring a saved VM on an older
version of QEMU will likely result in silent guest failure.

This patch introduces a new version of the savevm protocol.  It has the
following features:

 * Support for progressive save of sections (for live checkpoint/migration)
 * An asynchronous API for doing save
 * Support for interleaving multiple progressive save sections
   (for future support of memory hot-add/storage migration)
 * Fully streaming format
 * Strong section version checking

Signed-off-by: Anthony Liguori <address@hidden>

Modified Paths:
--------------
    trunk/hw/hw.h
    trunk/sysemu.h
    trunk/vl.c

Modified: trunk/hw/hw.h
===================================================================
--- trunk/hw/hw.h       2008-10-06 14:02:03 UTC (rev 5433)
+++ trunk/hw/hw.h       2008-10-06 14:53:52 UTC (rev 5434)
@@ -217,6 +217,7 @@
 int64_t qemu_fseek(QEMUFile *f, int64_t pos, int whence);
 
 typedef void SaveStateHandler(QEMUFile *f, void *opaque);
+typedef int SaveLiveStateHandler(QEMUFile *f, int stage, void *opaque);
 typedef int LoadStateHandler(QEMUFile *f, void *opaque, int version_id);
 
 int register_savevm(const char *idstr,
@@ -226,6 +227,14 @@
                     LoadStateHandler *load_state,
                     void *opaque);
 
+int register_savevm_live(const char *idstr,
+                         int instance_id,
+                         int version_id,
+                         SaveLiveStateHandler *save_live_state,
+                         SaveStateHandler *save_state,
+                         LoadStateHandler *load_state,
+                         void *opaque);
+
 typedef void QEMUResetHandler(void *opaque);
 
 void qemu_register_reset(QEMUResetHandler *func, void *opaque);

Modified: trunk/sysemu.h
===================================================================
--- trunk/sysemu.h      2008-10-06 14:02:03 UTC (rev 5433)
+++ trunk/sysemu.h      2008-10-06 14:53:52 UTC (rev 5434)
@@ -50,6 +50,12 @@
 
 void main_loop_wait(int timeout);
 
+int qemu_savevm_state_begin(QEMUFile *f);
+int qemu_savevm_state_iterate(QEMUFile *f);
+int qemu_savevm_state_complete(QEMUFile *f);
+int qemu_savevm_state(QEMUFile *f);
+int qemu_loadvm_state(QEMUFile *f);
+
 /* Polling handling */
 
 /* return TRUE if no sleep should be done afterwards */

Modified: trunk/vl.c
===================================================================
--- trunk/vl.c  2008-10-06 14:02:03 UTC (rev 5433)
+++ trunk/vl.c  2008-10-06 14:53:52 UTC (rev 5434)
@@ -6579,6 +6579,8 @@
     char idstr[256];
     int instance_id;
     int version_id;
+    int section_id;
+    SaveLiveStateHandler *save_live_state;
     SaveStateHandler *save_state;
     LoadStateHandler *load_state;
     void *opaque;
@@ -6591,14 +6593,16 @@
    of the system, so instance_id should be removed/replaced.
    Meanwhile pass -1 as instance_id if you do not already have a clearly
    distinguishing id for all instances of your device class. */
-int register_savevm(const char *idstr,
-                    int instance_id,
-                    int version_id,
-                    SaveStateHandler *save_state,
-                    LoadStateHandler *load_state,
-                    void *opaque)
+int register_savevm_live(const char *idstr,
+                         int instance_id,
+                         int version_id,
+                         SaveLiveStateHandler *save_live_state,
+                         SaveStateHandler *save_state,
+                         LoadStateHandler *load_state,
+                         void *opaque)
 {
     SaveStateEntry *se, **pse;
+    static int global_section_id;
 
     se = qemu_malloc(sizeof(SaveStateEntry));
     if (!se)
@@ -6606,6 +6610,8 @@
     pstrcpy(se->idstr, sizeof(se->idstr), idstr);
     se->instance_id = (instance_id == -1) ? 0 : instance_id;
     se->version_id = version_id;
+    se->section_id = global_section_id++;
+    se->save_live_state = save_live_state;
     se->save_state = save_state;
     se->load_state = load_state;
     se->opaque = opaque;
@@ -6624,25 +6630,105 @@
     return 0;
 }
 
-#define QEMU_VM_FILE_MAGIC   0x5145564d
-#define QEMU_VM_FILE_VERSION 0x00000002
+int register_savevm(const char *idstr,
+                    int instance_id,
+                    int version_id,
+                    SaveStateHandler *save_state,
+                    LoadStateHandler *load_state,
+                    void *opaque)
+{
+    return register_savevm_live(idstr, instance_id, version_id,
+                                NULL, save_state, load_state, opaque);
+}
 
-static int qemu_savevm_state(QEMUFile *f)
+#define QEMU_VM_FILE_MAGIC           0x5145564d
+#define QEMU_VM_FILE_VERSION_COMPAT  0x00000002
+#define QEMU_VM_FILE_VERSION         0x00000003
+
+#define QEMU_VM_EOF                  0x00
+#define QEMU_VM_SECTION_START        0x01
+#define QEMU_VM_SECTION_PART         0x02
+#define QEMU_VM_SECTION_END          0x03
+#define QEMU_VM_SECTION_FULL         0x04
+
+int qemu_savevm_state_begin(QEMUFile *f)
 {
     SaveStateEntry *se;
-    int len, ret;
-    int64_t cur_pos, len_pos, total_len_pos;
 
     qemu_put_be32(f, QEMU_VM_FILE_MAGIC);
     qemu_put_be32(f, QEMU_VM_FILE_VERSION);
-    total_len_pos = qemu_ftell(f);
-    qemu_put_be64(f, 0); /* total size */
 
+    for (se = first_se; se != NULL; se = se->next) {
+        int len;
+
+        if (se->save_live_state == NULL)
+            continue;
+
+        /* Section type */
+        qemu_put_byte(f, QEMU_VM_SECTION_START);
+        qemu_put_be32(f, se->section_id);
+
+        /* ID string */
+        len = strlen(se->idstr);
+        qemu_put_byte(f, len);
+        qemu_put_buffer(f, (uint8_t *)se->idstr, len);
+
+        qemu_put_be32(f, se->instance_id);
+        qemu_put_be32(f, se->version_id);
+
+        se->save_live_state(f, QEMU_VM_SECTION_START, se->opaque);
+    }
+
+    return 0;
+}
+
+int qemu_savevm_state_iterate(QEMUFile *f)
+{
+    SaveStateEntry *se;
+    int ret = 0;
+
+    for (se = first_se; se != NULL; se = se->next) {
+        if (se->save_live_state == NULL)
+            continue;
+
+        /* Section type */
+        qemu_put_byte(f, QEMU_VM_SECTION_PART);
+        qemu_put_be32(f, se->section_id);
+
+        ret |= se->save_live_state(f, QEMU_VM_SECTION_PART, se->opaque);
+    }
+
+    if (ret)
+        return 1;
+
+    return 0;
+}
+
+int qemu_savevm_state_complete(QEMUFile *f)
+{
+    SaveStateEntry *se;
+
+    for (se = first_se; se != NULL; se = se->next) {
+        if (se->save_live_state == NULL)
+            continue;
+
+        /* Section type */
+        qemu_put_byte(f, QEMU_VM_SECTION_END);
+        qemu_put_be32(f, se->section_id);
+
+        se->save_live_state(f, QEMU_VM_SECTION_END, se->opaque);
+    }
+
     for(se = first_se; se != NULL; se = se->next) {
+        int len;
+
        if (se->save_state == NULL)
-           /* this one has a loader only, for backwards compatibility */
            continue;
 
+        /* Section type */
+        qemu_put_byte(f, QEMU_VM_SECTION_FULL);
+        qemu_put_be32(f, se->section_id);
+
         /* ID string */
         len = strlen(se->idstr);
         qemu_put_byte(f, len);
@@ -6651,24 +6737,37 @@
         qemu_put_be32(f, se->instance_id);
         qemu_put_be32(f, se->version_id);
 
-        /* record size: filled later */
-        len_pos = qemu_ftell(f);
-        qemu_put_be32(f, 0);
         se->save_state(f, se->opaque);
-
-        /* fill record size */
-        cur_pos = qemu_ftell(f);
-        len = cur_pos - len_pos - 4;
-        qemu_fseek(f, len_pos, SEEK_SET);
-        qemu_put_be32(f, len);
-        qemu_fseek(f, cur_pos, SEEK_SET);
     }
-    cur_pos = qemu_ftell(f);
-    qemu_fseek(f, total_len_pos, SEEK_SET);
-    qemu_put_be64(f, cur_pos - total_len_pos - 8);
-    qemu_fseek(f, cur_pos, SEEK_SET);
 
-    ret = 0;
+    qemu_put_byte(f, QEMU_VM_EOF);
+
+    return 0;
+}
+
+int qemu_savevm_state(QEMUFile *f)
+{
+    int saved_vm_running;
+    int ret;
+
+    saved_vm_running = vm_running;
+    vm_stop(0);
+
+    ret = qemu_savevm_state_begin(f);
+    if (ret < 0)
+        goto out;
+
+    do {
+        ret = qemu_savevm_state_iterate(f);
+        if (ret < 0)
+            goto out;
+    } while (ret == 1);
+
+    ret = qemu_savevm_state_complete(f);
+
+out:
+    if (saved_vm_running)
+        vm_start();
     return ret;
 }
 
@@ -6684,23 +6783,20 @@
     return NULL;
 }
 
-static int qemu_loadvm_state(QEMUFile *f)
+typedef struct LoadStateEntry {
+    SaveStateEntry *se;
+    int section_id;
+    int version_id;
+    struct LoadStateEntry *next;
+} LoadStateEntry;
+
+static int qemu_loadvm_state_v2(QEMUFile *f)
 {
     SaveStateEntry *se;
     int len, ret, instance_id, record_len, version_id;
     int64_t total_len, end_pos, cur_pos;
-    unsigned int v;
     char idstr[256];
 
-    v = qemu_get_be32(f);
-    if (v != QEMU_VM_FILE_MAGIC)
-        goto fail;
-    v = qemu_get_be32(f);
-    if (v != QEMU_VM_FILE_VERSION) {
-    fail:
-        ret = -1;
-        goto the_end;
-    }
     total_len = qemu_get_be64(f);
     end_pos = total_len + qemu_ftell(f);
     for(;;) {
@@ -6712,10 +6808,6 @@
         instance_id = qemu_get_be32(f);
         version_id = qemu_get_be32(f);
         record_len = qemu_get_be32(f);
-#if 0
-        printf("idstr=%s instance=0x%x version=%d len=%d\n",
-               idstr, instance_id, version_id, record_len);
-#endif
         cur_pos = qemu_ftell(f);
         se = find_se(idstr, instance_id);
         if (!se) {
@@ -6731,8 +6823,104 @@
         /* always seek to exact end of record */
         qemu_fseek(f, cur_pos + record_len, SEEK_SET);
     }
+    return 0;
+}
+
+int qemu_loadvm_state(QEMUFile *f)
+{
+    LoadStateEntry *first_le = NULL;
+    uint8_t section_type;
+    unsigned int v;
+    int ret;
+
+    v = qemu_get_be32(f);
+    if (v != QEMU_VM_FILE_MAGIC)
+        return -EINVAL;
+
+    v = qemu_get_be32(f);
+    if (v == QEMU_VM_FILE_VERSION_COMPAT)
+        return qemu_loadvm_state_v2(f);
+    if (v != QEMU_VM_FILE_VERSION)
+        return -ENOTSUP;
+
+    while ((section_type = qemu_get_byte(f)) != QEMU_VM_EOF) {
+        uint32_t instance_id, version_id, section_id;
+        LoadStateEntry *le;
+        SaveStateEntry *se;
+        char idstr[257];
+        int len;
+
+        switch (section_type) {
+        case QEMU_VM_SECTION_START:
+        case QEMU_VM_SECTION_FULL:
+            /* Read section start */
+            section_id = qemu_get_be32(f);
+            len = qemu_get_byte(f);
+            qemu_get_buffer(f, (uint8_t *)idstr, len);
+            idstr[len] = 0;
+            instance_id = qemu_get_be32(f);
+            version_id = qemu_get_be32(f);
+
+            /* Find savevm section */
+            se = find_se(idstr, instance_id);
+            if (se == NULL) {
+                fprintf(stderr, "Unknown savevm section or instance '%s' 
%d\n", idstr, instance_id);
+                ret = -EINVAL;
+                goto out;
+            }
+
+            /* Validate version */
+            if (version_id > se->version_id) {
+                fprintf(stderr, "savevm: unsupported version %d for '%s' 
v%d\n",
+                        version_id, idstr, se->version_id);
+                ret = -EINVAL;
+                goto out;
+            }
+
+            /* Add entry */
+            le = qemu_mallocz(sizeof(*le));
+            if (le == NULL) {
+                ret = -ENOMEM;
+                goto out;
+            }
+
+            le->se = se;
+            le->section_id = section_id;
+            le->version_id = version_id;
+            le->next = first_le;
+            first_le = le;
+
+            le->se->load_state(f, le->se->opaque, le->version_id);
+            break;
+        case QEMU_VM_SECTION_PART:
+        case QEMU_VM_SECTION_END:
+            section_id = qemu_get_be32(f);
+
+            for (le = first_le; le && le->section_id != section_id; le = 
le->next);
+            if (le == NULL) {
+                fprintf(stderr, "Unknown savevm section %d\n", section_id);
+                ret = -EINVAL;
+                goto out;
+            }
+
+            le->se->load_state(f, le->se->opaque, le->version_id);
+            break;
+        default:
+            fprintf(stderr, "Unknown savevm section type %d\n", section_type);
+            ret = -EINVAL;
+            goto out;
+        }
+    }
+
     ret = 0;
- the_end:
+
+out:
+    while (first_le) {
+        LoadStateEntry *le = first_le;
+        first_le = first_le->next;
+        qemu_free(le);
+    }
+
     return ret;
 }