migration/next for 20140225

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Merge remote-tracking branch 'remotes/juanquintela/tags/migration/20140225' into staging

migration/next for 20140225

# gpg: Signature made Tue 25 Feb 2014 14:04:31 GMT using RSA key ID 5872D723
# gpg: Can't check signature: public key not found

* remotes/juanquintela/tags/migration/20140225:
  rdma: rename 'x-rdma' => 'rdma'
  Fix two XBZRLE corruption issues
  Fix vmstate_info_int32_le comparison/assign
  qemu_file: use fwrite() correctly

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

arch_init.c

@@ -122,7 +122,6 @@ static void check_guest_throttling(void);
 #define RAM_SAVE_FLAG_XBZRLE   0x40
 /* 0x80 is reserved in migration.h start with 0x100 next */
 
-
 static struct defconfig_file {
     const char *filename;
     /* Indicates it is an user config file (disabled by -no-user-config) */
@@ -133,6 +132,7 @@ static struct defconfig_file {
     { NULL }, /* end of list */
 };
 
+static const uint8_t ZERO_TARGET_PAGE[TARGET_PAGE_SIZE];
 
 int qemu_read_default_config_files(bool userconfig)
 {
@@ -273,6 +273,34 @@ static size_t save_block_hdr(QEMUFile *f, RAMBlock *block, ram_addr_t offset,
     return size;
 }
 
+/* This is the last block that we have visited serching for dirty pages
+ */
+static RAMBlock *last_seen_block;
+/* This is the last block from where we have sent data */
+static RAMBlock *last_sent_block;
+static ram_addr_t last_offset;
+static unsigned long *migration_bitmap;
+static uint64_t migration_dirty_pages;
+static uint32_t last_version;
+static bool ram_bulk_stage;
+
+/* Update the xbzrle cache to reflect a page that's been sent as all 0.
+ * The important thing is that a stale (not-yet-0'd) page be replaced
+ * by the new data.
+ * As a bonus, if the page wasn't in the cache it gets added so that
+ * when a small write is made into the 0'd page it gets XBZRLE sent
+ */
+static void xbzrle_cache_zero_page(ram_addr_t current_addr)
+{
+    if (ram_bulk_stage || !migrate_use_xbzrle()) {
+        return;
+    }
+
+    /* We don't care if this fails to allocate a new cache page
+     * as long as it updated an old one */
+    cache_insert(XBZRLE.cache, current_addr, ZERO_TARGET_PAGE);
+}
+
 #define ENCODING_FLAG_XBZRLE 0x1
 
 static int save_xbzrle_page(QEMUFile *f, uint8_t *current_data,
@@ -329,18 +357,6 @@ static int save_xbzrle_page(QEMUFile *f, uint8_t *current_data,
     return bytes_sent;
 }
 
-
-/* This is the last block that we have visited serching for dirty pages
- */
-static RAMBlock *last_seen_block;
-/* This is the last block from where we have sent data */
-static RAMBlock *last_sent_block;
-static ram_addr_t last_offset;
-static unsigned long *migration_bitmap;
-static uint64_t migration_dirty_pages;
-static uint32_t last_version;
-static bool ram_bulk_stage;
-
 static inline
 ram_addr_t migration_bitmap_find_and_reset_dirty(MemoryRegion *mr,
                                                  ram_addr_t start)
@@ -512,6 +528,7 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
         } else {
             int ret;
             uint8_t *p;
+            bool send_async = true;
             int cont = (block == last_sent_block) ?
                 RAM_SAVE_FLAG_CONTINUE : 0;
 
@@ -522,6 +539,7 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
             ret = ram_control_save_page(f, block->offset,
                                offset, TARGET_PAGE_SIZE, &bytes_sent);
 
+            current_addr = block->offset + offset;
             if (ret != RAM_SAVE_CONTROL_NOT_SUPP) {
                 if (ret != RAM_SAVE_CONTROL_DELAYED) {
                     if (bytes_sent > 0) {
@@ -536,19 +554,35 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
                                             RAM_SAVE_FLAG_COMPRESS);
                 qemu_put_byte(f, 0);
                 bytes_sent++;
+                /* Must let xbzrle know, otherwise a previous (now 0'd) cached
+                 * page would be stale
+                 */
+                xbzrle_cache_zero_page(current_addr);
             } else if (!ram_bulk_stage && migrate_use_xbzrle()) {
-                current_addr = block->offset + offset;
                 bytes_sent = save_xbzrle_page(f, p, current_addr, block,
                                               offset, cont, last_stage);
                 if (!last_stage) {
+                    /* We must send exactly what's in the xbzrle cache
+                     * even if the page wasn't xbzrle compressed, so that
+                     * it's right next time.
+                     */
                     p = get_cached_data(XBZRLE.cache, current_addr);
+
+                    /* Can't send this cached data async, since the cache page
+                     * might get updated before it gets to the wire
+                     */
+                    send_async = false;
                 }
             }
 
             /* XBZRLE overflow or normal page */
             if (bytes_sent == -1) {
                 bytes_sent = save_block_hdr(f, block, offset, cont, RAM_SAVE_FLAG_PAGE);
-                qemu_put_buffer_async(f, p, TARGET_PAGE_SIZE);
+                if (send_async) {
+                    qemu_put_buffer_async(f, p, TARGET_PAGE_SIZE);
+                } else {
+                    qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
+                }
                 bytes_sent += TARGET_PAGE_SIZE;
                 acct_info.norm_pages++;
             }

docs/rdma.txt

@@ -66,7 +66,7 @@ bulk-phase round of the migration and can be enabled for extremely
 high-performance RDMA hardware using the following command:
 
 QEMU Monitor Command:
-$ migrate_set_capability x-rdma-pin-all on # disabled by default
+$ migrate_set_capability rdma-pin-all on # disabled by default
 
 Performing this action will cause all 8GB to be pinned, so if that's
 not what you want, then please ignore this step altogether.
@@ -93,12 +93,12 @@ $ migrate_set_speed 40g # or whatever is the MAX of your RDMA device
 
 Next, on the destination machine, add the following to the QEMU command line:
 
-qemu ..... -incoming x-rdma:host:port
+qemu ..... -incoming rdma:host:port
 
 Finally, perform the actual migration on the source machine:
 
 QEMU Monitor Command:
-$ migrate -d x-rdma:host:port
+$ migrate -d rdma:host:port
 
 PERFORMANCE
 ===========
@@ -120,8 +120,8 @@ For example, in the same 8GB RAM example with all 8GB of memory in
 active use and the VM itself is completely idle using the same 40 gbps
 infiniband link:
 
-1. x-rdma-pin-all disabled total time: approximately 7.5 seconds @ 9.5 Gbps
+1. rdma-pin-all disabled total time: approximately 7.5 seconds @ 9.5 Gbps
-2. x-rdma-pin-all enabled total time: approximately 4 seconds @ 26 Gbps
+2. rdma-pin-all enabled total time: approximately 4 seconds @ 26 Gbps
 
 These numbers would of course scale up to whatever size virtual machine
 you have to migrate using RDMA.
@@ -407,18 +407,14 @@ socket is broken during a non-RDMA based migration.
 
 TODO:
 =====
-1. 'migrate x-rdma:host:port' and '-incoming x-rdma' options will be
+1. Currently, 'ulimit -l' mlock() limits as well as cgroups swap limits
-   renamed to 'rdma' after the experimental phase of this work has
-   completed upstream.
-2. Currently, 'ulimit -l' mlock() limits as well as cgroups swap limits
    are not compatible with infinband memory pinning and will result in
    an aborted migration (but with the source VM left unaffected).
-3. Use of the recent /proc/<pid>/pagemap would likely speed up
+2. Use of the recent /proc/<pid>/pagemap would likely speed up
    the use of KSM and ballooning while using RDMA.
-4. Also, some form of balloon-device usage tracking would also
+3. Also, some form of balloon-device usage tracking would also
    help alleviate some issues.
-5. Move UNREGISTER requests to a separate thread.
+4. Use LRU to provide more fine-grained direction of UNREGISTER
-6. Use LRU to provide more fine-grained direction of UNREGISTER
    requests for unpinning memory in an overcommitted environment.
-7. Expose UNREGISTER support to the user by way of workload-specific
+5. Expose UNREGISTER support to the user by way of workload-specific
    hints about application behavior.

include/migration/page_cache.h

@@ -66,7 +66,7 @@ uint8_t *get_cached_data(const PageCache *cache, uint64_t addr);
  * @addr: page address
  * @pdata: pointer to the page
  */
-int cache_insert(PageCache *cache, uint64_t addr, uint8_t *pdata);
+int cache_insert(PageCache *cache, uint64_t addr, const uint8_t *pdata);
 
 /**
  * cache_resize: resize the page cache. In case of size reduction the extra

migration-rdma.c

@@ -3412,7 +3412,7 @@ void rdma_start_outgoing_migration(void *opaque,
     }
 
     ret = qemu_rdma_source_init(rdma, &local_err,
-        s->enabled_capabilities[MIGRATION_CAPABILITY_X_RDMA_PIN_ALL]);
+        s->enabled_capabilities[MIGRATION_CAPABILITY_RDMA_PIN_ALL]);
 
     if (ret) {
         goto err;

migration.c

@@ -82,7 +82,7 @@ void qemu_start_incoming_migration(const char *uri, Error **errp)
     if (strstart(uri, "tcp:", &p))
         tcp_start_incoming_migration(p, errp);
 #ifdef CONFIG_RDMA
-    else if (strstart(uri, "x-rdma:", &p))
+    else if (strstart(uri, "rdma:", &p))
         rdma_start_incoming_migration(p, errp);
 #endif
 #if !defined(WIN32)
@@ -438,7 +438,7 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
     if (strstart(uri, "tcp:", &p)) {
         tcp_start_outgoing_migration(s, p, &local_err);
 #ifdef CONFIG_RDMA
-    } else if (strstart(uri, "x-rdma:", &p)) {
+    } else if (strstart(uri, "rdma:", &p)) {
         rdma_start_outgoing_migration(s, p, &local_err);
 #endif
 #if !defined(WIN32)
@@ -532,7 +532,7 @@ bool migrate_rdma_pin_all(void)
 
     s = migrate_get_current();
 
-    return s->enabled_capabilities[MIGRATION_CAPABILITY_X_RDMA_PIN_ALL];
+    return s->enabled_capabilities[MIGRATION_CAPABILITY_RDMA_PIN_ALL];
 }
 
 bool migrate_auto_converge(void)

page_cache.c

@@ -150,7 +150,7 @@ uint8_t *get_cached_data(const PageCache *cache, uint64_t addr)
     return cache_get_by_addr(cache, addr)->it_data;
 }
 
-int cache_insert(PageCache *cache, uint64_t addr, uint8_t *pdata)
+int cache_insert(PageCache *cache, uint64_t addr, const uint8_t *pdata)
 {
 
     CacheItem *it = NULL;

qapi-schema.json

@@ -751,10 +751,9 @@
 #          This feature allows us to minimize migration traffic for certain work
 #          loads, by sending compressed difference of the pages
 #
-# @x-rdma-pin-all: Controls whether or not the entire VM memory footprint is
+# @rdma-pin-all: Controls whether or not the entire VM memory footprint is
 #          mlock()'d on demand or all at once. Refer to docs/rdma.txt for usage.
-#          Disabled by default. Experimental: may (or may not) be renamed after
+#          Disabled by default. (since 2.0)
-#          further testing is complete. (since 1.6)
 #
 # @zero-blocks: During storage migration encode blocks of zeroes efficiently. This
 #          essentially saves 1MB of zeroes per block on the wire. Enabling requires
@@ -768,7 +767,7 @@
 # Since: 1.2
 ##
 { 'enum': 'MigrationCapability',
-  'data': ['xbzrle', 'x-rdma-pin-all', 'auto-converge', 'zero-blocks'] }
+  'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', 'zero-blocks'] }
 
 ##
 # @MigrationCapabilityStatus

qemu-file.c

@@ -100,7 +100,14 @@ static int stdio_put_buffer(void *opaque, const uint8_t *buf, int64_t pos,
                             int size)
 {
     QEMUFileStdio *s = opaque;
-    return fwrite(buf, 1, size, s->stdio_file);
+    int res;
+
+    res = fwrite(buf, 1, size, s->stdio_file);
+
+    if (res != size) {
+        return -EIO;	/* fake errno value */
+    }
+    return res;
 }
 
 static int stdio_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)

vmstate.c

@@ -321,23 +321,24 @@ const VMStateInfo vmstate_info_int32_equal = {
     .put  = put_int32,
 };
 
-/* 32 bit int. See that the received value is the less or the same
+/* 32 bit int. Check that the received value is less than or equal to
-   than the one in the field */
+   the one in the field */
 
 static int get_int32_le(QEMUFile *f, void *pv, size_t size)
 {
-    int32_t *old = pv;
+    int32_t *cur = pv;
-    int32_t new;
+    int32_t loaded;
-    qemu_get_sbe32s(f, &new);
+    qemu_get_sbe32s(f, &loaded);
 
-    if (*old <= new) {
+    if (loaded <= *cur) {
+        *cur = loaded;
         return 0;
     }
     return -EINVAL;
 }
 
 const VMStateInfo vmstate_info_int32_le = {
-    .name = "int32 equal",
+    .name = "int32 le",
     .get  = get_int32_le,
     .put  = put_int32,
 };