Merge remote-tracking branch 'remotes/dgilbert/tags/pull-migration-20201026a' into staging

migration pull: 2020-10-26

Another go at Peter's postcopy fixes

Cleanups from Bihong Yu and Peter Maydell.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

# gpg: Signature made Mon 26 Oct 2020 16:17:03 GMT
# gpg:                using RSA key 45F5C71B4A0CB7FB977A9FA90516331EBC5BFDE7
# gpg: Good signature from "Dr. David Alan Gilbert (RH2) <dgilbert@redhat.com>" [full]
# Primary key fingerprint: 45F5 C71B 4A0C B7FB 977A  9FA9 0516 331E BC5B FDE7

* remotes/dgilbert/tags/pull-migration-20201026a:
  migration-test: Only hide error if !QTEST_LOG
  migration/postcopy: Release fd before going into 'postcopy-pause'
  migration: Sync requested pages after postcopy recovery
  migration: Maintain postcopy faulted addresses
  migration: Introduce migrate_send_rp_message_req_pages()
  migration: Pass incoming state into qemu_ufd_copy_ioctl()
  migration: using trace_ to replace DPRINTF
  migration: Delete redundant spaces
  migration: Open brace '{' following function declarations go on the next line
  migration: Do not initialise statics and globals to 0 or NULL
  migration: Add braces {} for if statement
  migration: Open brace '{' following struct go on the same line
  migration: Add spaces around operator
  migration: Don't use '#' flag of printf format
  migration: Do not use C99 // comments
  migration: Drop unused VMSTATE_FLOAT64 support

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

13 files changed, 213 insertions, 103 deletions

diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index f68ed7db13..4d71dc8fba 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -219,7 +219,6 @@ extern const VMStateInfo vmstate_info_uint64;
 #define VMS_NULLPTR_MARKER (0x30U) /* '0' */
 extern const VMStateInfo vmstate_info_nullptr;
 
-extern const VMStateInfo vmstate_info_float64;
 extern const VMStateInfo vmstate_info_cpudouble;
 
 extern const VMStateInfo vmstate_info_timer;
@@ -997,12 +996,6 @@ extern const VMStateInfo vmstate_info_qlist;
     VMSTATE_SINGLE_TEST(_f, _s, _t, 0, vmstate_info_uint64, uint64_t)
 
 
-#define VMSTATE_FLOAT64_V(_f, _s, _v)                                 \
-    VMSTATE_SINGLE(_f, _s, _v, vmstate_info_float64, float64)
-
-#define VMSTATE_FLOAT64(_f, _s)                                       \
-    VMSTATE_FLOAT64_V(_f, _s, 0)
-
 #define VMSTATE_TIMER_PTR_TEST(_f, _s, _test)                             \
     VMSTATE_POINTER_TEST(_f, _s, _test, vmstate_info_timer, QEMUTimer *)
 
@@ -1114,12 +1107,6 @@ extern const VMStateInfo vmstate_info_qlist;
 #define VMSTATE_INT64_ARRAY(_f, _s, _n)                               \
     VMSTATE_INT64_ARRAY_V(_f, _s, _n, 0)
 
-#define VMSTATE_FLOAT64_ARRAY_V(_f, _s, _n, _v)                       \
-    VMSTATE_ARRAY(_f, _s, _n, _v, vmstate_info_float64, float64)
-
-#define VMSTATE_FLOAT64_ARRAY(_f, _s, _n)                             \
-    VMSTATE_FLOAT64_ARRAY_V(_f, _s, _n, 0)
-
 #define VMSTATE_CPUDOUBLE_ARRAY_V(_f, _s, _n, _v)                     \
     VMSTATE_ARRAY(_f, _s, _n, _v, vmstate_info_cpudouble, CPU_DoubleU)
 
diff --git a/migration/block.c b/migration/block.c
index 737b6499f9..a950977855 100644
--- a/migration/block.c
+++ b/migration/block.c
@@ -26,6 +26,7 @@
 #include "qemu-file.h"
 #include "migration/vmstate.h"
 #include "sysemu/block-backend.h"
+#include "trace.h"
 
 #define BLK_MIG_BLOCK_SIZE           (1 << 20)
 #define BDRV_SECTORS_PER_DIRTY_CHUNK (BLK_MIG_BLOCK_SIZE >> BDRV_SECTOR_BITS)
@@ -40,7 +41,7 @@
 #define MAX_IO_BUFFERS 512
 #define MAX_PARALLEL_IO 16
 
-//#define DEBUG_BLK_MIGRATION
+/* #define DEBUG_BLK_MIGRATION */
 
 #ifdef DEBUG_BLK_MIGRATION
 #define DPRINTF(fmt, ...) \
@@ -434,10 +435,9 @@ static int init_blk_migration(QEMUFile *f)
         block_mig_state.total_sector_sum += sectors;
 
         if (bmds->shared_base) {
-            DPRINTF("Start migration for %s with shared base image\n",
-                    bdrv_get_device_name(bs));
+            trace_migration_block_init_shared(bdrv_get_device_name(bs));
         } else {
-            DPRINTF("Start full migration for %s\n", bdrv_get_device_name(bs));
+            trace_migration_block_init_full(bdrv_get_device_name(bs));
         }
 
         QSIMPLEQ_INSERT_TAIL(&block_mig_state.bmds_list, bmds, entry);
@@ -592,7 +592,7 @@ static int mig_save_device_dirty(QEMUFile *f, BlkMigDevState *bmds,
     return (bmds->cur_dirty >= bmds->total_sectors);
 
 error:
-    DPRINTF("Error reading sector %" PRId64 "\n", sector);
+    trace_migration_block_save_device_dirty(sector);
     g_free(blk->buf);
     g_free(blk);
     return ret;
@@ -628,9 +628,9 @@ static int flush_blks(QEMUFile *f)
     BlkMigBlock *blk;
     int ret = 0;
 
-    DPRINTF("%s Enter submitted %d read_done %d transferred %d\n",
-            __func__, block_mig_state.submitted, block_mig_state.read_done,
-            block_mig_state.transferred);
+    trace_migration_block_flush_blks("Enter", block_mig_state.submitted,
+                                     block_mig_state.read_done,
+                                     block_mig_state.transferred);
 
     blk_mig_lock();
     while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) {
@@ -656,9 +656,9 @@ static int flush_blks(QEMUFile *f)
     }
     blk_mig_unlock();
 
-    DPRINTF("%s Exit submitted %d read_done %d transferred %d\n", __func__,
-            block_mig_state.submitted, block_mig_state.read_done,
-            block_mig_state.transferred);
+    trace_migration_block_flush_blks("Exit", block_mig_state.submitted,
+                                     block_mig_state.read_done,
+                                     block_mig_state.transferred);
     return ret;
 }
 
@@ -727,8 +727,8 @@ static int block_save_setup(QEMUFile *f, void *opaque)
 {
     int ret;
 
-    DPRINTF("Enter save live setup submitted %d transferred %d\n",
-            block_mig_state.submitted, block_mig_state.transferred);
+    trace_migration_block_save("setup", block_mig_state.submitted,
+                               block_mig_state.transferred);
 
     qemu_mutex_lock_iothread();
     ret = init_blk_migration(f);
@@ -759,8 +759,8 @@ static int block_save_iterate(QEMUFile *f, void *opaque)
     int64_t last_ftell = qemu_ftell(f);
     int64_t delta_ftell;
 
-    DPRINTF("Enter save live iterate submitted %d transferred %d\n",
-            block_mig_state.submitted, block_mig_state.transferred);
+    trace_migration_block_save("iterate", block_mig_state.submitted,
+                               block_mig_state.transferred);
 
     ret = flush_blks(f);
     if (ret) {
@@ -825,8 +825,8 @@ static int block_save_complete(QEMUFile *f, void *opaque)
 {
     int ret;
 
-    DPRINTF("Enter save live complete submitted %d transferred %d\n",
-            block_mig_state.submitted, block_mig_state.transferred);
+    trace_migration_block_save("complete", block_mig_state.submitted,
+                               block_mig_state.transferred);
 
     ret = flush_blks(f);
     if (ret) {
@@ -851,7 +851,7 @@ static int block_save_complete(QEMUFile *f, void *opaque)
     /* report completion */
     qemu_put_be64(f, (100 << BDRV_SECTOR_BITS) | BLK_MIG_FLAG_PROGRESS);
 
-    DPRINTF("Block migration completed\n");
+    trace_migration_block_save_complete();
 
     qemu_put_be64(f, BLK_MIG_FLAG_EOS);
 
@@ -884,7 +884,7 @@ static void block_save_pending(QEMUFile *f, void *opaque, uint64_t max_size,
         pending = max_size + BLK_MIG_BLOCK_SIZE;
     }
 
-    DPRINTF("Enter save live pending  %" PRIu64 "\n", pending);
+    trace_migration_block_save_pending(pending);
     /* We don't do postcopy */
     *res_precopy_only += pending;
 }
@@ -998,7 +998,7 @@ static int block_load(QEMUFile *f, void *opaque, int version_id)
                    (addr == 100) ? '\n' : '\r');
             fflush(stdout);
         } else if (!(flags & BLK_MIG_FLAG_EOS)) {
-            fprintf(stderr, "Unknown block migration flags: %#x\n", flags);
+            fprintf(stderr, "Unknown block migration flags: 0x%x\n", flags);
             return -EINVAL;
         }
         ret = qemu_file_get_error(f);
diff --git a/migration/migration.c b/migration/migration.c
index deb6005b8d..9bb4fee5ac 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -143,6 +143,13 @@ static int migration_maybe_pause(MigrationState *s,
                                  int new_state);
 static void migrate_fd_cancel(MigrationState *s);
 
+static gint page_request_addr_cmp(gconstpointer ap, gconstpointer bp)
+{
+    uintptr_t a = (uintptr_t) ap, b = (uintptr_t) bp;
+
+    return (a > b) - (a < b);
+}
+
 void migration_object_init(void)
 {
     Error *err = NULL;
@@ -164,6 +171,8 @@ void migration_object_init(void)
     qemu_event_init(&current_incoming->main_thread_load_event, false);
     qemu_sem_init(&current_incoming->postcopy_pause_sem_dst, 0);
     qemu_sem_init(&current_incoming->postcopy_pause_sem_fault, 0);
+    qemu_mutex_init(&current_incoming->page_request_mutex);
+    current_incoming->page_requested = g_tree_new(page_request_addr_cmp);
 
     if (!migration_object_check(current_migration, &err)) {
         error_report_err(err);
@@ -230,6 +239,11 @@ void migration_incoming_state_destroy(void)
 
     qemu_event_reset(&mis->main_thread_load_event);
 
+    if (mis->page_requested) {
+        g_tree_destroy(mis->page_requested);
+        mis->page_requested = NULL;
+    }
+
     if (mis->socket_address_list) {
         qapi_free_SocketAddressList(mis->socket_address_list);
         mis->socket_address_list = NULL;
@@ -306,8 +320,8 @@ error:
  *   Start: Address offset within the RB
  *   Len: Length in bytes required - must be a multiple of pagesize
  */
-int migrate_send_rp_req_pages(MigrationIncomingState *mis, RAMBlock *rb,
-                              ram_addr_t start)
+int migrate_send_rp_message_req_pages(MigrationIncomingState *mis,
+                                      RAMBlock *rb, ram_addr_t start)
 {
     uint8_t bufc[12 + 1 + 255]; /* start (8), len (4), rbname up to 256 */
     size_t msglen = 12; /* start + len */
@@ -343,6 +357,37 @@ int migrate_send_rp_req_pages(MigrationIncomingState *mis, RAMBlock *rb,
     return migrate_send_rp_message(mis, msg_type, msglen, bufc);
 }
 
+int migrate_send_rp_req_pages(MigrationIncomingState *mis,
+                              RAMBlock *rb, ram_addr_t start, uint64_t haddr)
+{
+    void *aligned = (void *)(uintptr_t)(haddr & (-qemu_ram_pagesize(rb)));
+    bool received;
+
+    WITH_QEMU_LOCK_GUARD(&mis->page_request_mutex) {
+        received = ramblock_recv_bitmap_test_byte_offset(rb, start);
+        if (!received && !g_tree_lookup(mis->page_requested, aligned)) {
+            /*
+             * The page has not been received, and it's not yet in the page
+             * request list.  Queue it.  Set the value of element to 1, so that
+             * things like g_tree_lookup() will return TRUE (1) when found.
+             */
+            g_tree_insert(mis->page_requested, aligned, (gpointer)1);
+            mis->page_requested_count++;
+            trace_postcopy_page_req_add(aligned, mis->page_requested_count);
+        }
+    }
+
+    /*
+     * If the page is there, skip sending the message.  We don't even need the
+     * lock because as long as the page arrived, it'll be there forever.
+     */
+    if (received) {
+        return 0;
+    }
+
+    return migrate_send_rp_message_req_pages(mis, rb, start);
+}
+
 static bool migration_colo_enabled;
 bool migration_incoming_colo_enabled(void)
 {
@@ -2468,8 +2513,8 @@ static void migrate_handle_rp_req_pages(MigrationState *ms, const char* rbname,
      * Since we currently insist on matching page sizes, just sanity check
      * we're being asked for whole host pages.
      */
-    if (start & (our_host_ps-1) ||
-       (len & (our_host_ps-1))) {
+    if (start & (our_host_ps - 1) ||
+       (len & (our_host_ps - 1))) {
         error_report("%s: Misaligned page request, start: " RAM_ADDR_FMT
                      " len: %zd", __func__, start, len);
         mark_source_rp_bad(ms);
@@ -3123,9 +3168,6 @@ static MigThrError postcopy_pause(MigrationState *s)
     while (true) {
         QEMUFile *file;
 
-        migrate_set_state(&s->state, s->state,
-                          MIGRATION_STATUS_POSTCOPY_PAUSED);
-
         /* Current channel is possibly broken. Release it. */
         assert(s->to_dst_file);
         qemu_mutex_lock(&s->qemu_file_lock);
@@ -3136,6 +3178,9 @@ static MigThrError postcopy_pause(MigrationState *s)
         qemu_file_shutdown(file);
         qemu_fclose(file);
 
+        migrate_set_state(&s->state, s->state,
+                          MIGRATION_STATUS_POSTCOPY_PAUSED);
+
         error_report("Detected IO failure for postcopy. "
                      "Migration paused.");
 
diff --git a/migration/migration.h b/migration/migration.h
index deb411aaad..d096b77f74 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -104,6 +104,23 @@ struct MigrationIncomingState {
 
     /* List of listening socket addresses  */
     SocketAddressList *socket_address_list;
+
+    /* A tree of pages that we requested to the source VM */
+    GTree *page_requested;
+    /* For debugging purpose only, but would be nice to keep */
+    int page_requested_count;
+    /*
+     * The mutex helps to maintain the requested pages that we sent to the
+     * source, IOW, to guarantee coherent between the page_requests tree and
+     * the per-ramblock receivedmap.  Note! This does not guarantee consistency
+     * of the real page copy procedures (using UFFDIO_[ZERO]COPY).  E.g., even
+     * if one bit in receivedmap is cleared, UFFDIO_COPY could have happened
+     * for that page already.  This is intended so that the mutex won't
+     * serialize and blocked by slow operations like UFFDIO_* ioctls.  However
+     * this should be enough to make sure the page_requested tree always
+     * contains valid information.
+     */
+    QemuMutex page_request_mutex;
 };
 
 MigrationIncomingState *migration_incoming_get_current(void);
@@ -124,8 +141,7 @@ struct MigrationClass {
     DeviceClass parent_class;
 };
 
-struct MigrationState
-{
+struct MigrationState {
     /*< private >*/
     DeviceState parent_obj;
 
@@ -332,7 +348,9 @@ void migrate_send_rp_shut(MigrationIncomingState *mis,
 void migrate_send_rp_pong(MigrationIncomingState *mis,
                           uint32_t value);
 int migrate_send_rp_req_pages(MigrationIncomingState *mis, RAMBlock *rb,
-                              ram_addr_t start);
+                              ram_addr_t start, uint64_t haddr);
+int migrate_send_rp_message_req_pages(MigrationIncomingState *mis,
+                                      RAMBlock *rb, ram_addr_t start);
 void migrate_send_rp_recv_bitmap(MigrationIncomingState *mis,
                                  char *block_name);
 void migrate_send_rp_resume_ack(MigrationIncomingState *mis, uint32_t value);
diff --git a/migration/page_cache.c b/migration/page_cache.c
index 775582f453..098b436223 100644
--- a/migration/page_cache.c
+++ b/migration/page_cache.c
@@ -18,14 +18,7 @@
 #include "qapi/error.h"
 #include "qemu/host-utils.h"
 #include "page_cache.h"
-
-#ifdef DEBUG_CACHE
-#define DPRINTF(fmt, ...) \
-    do { fprintf(stdout, "cache: " fmt, ## __VA_ARGS__); } while (0)
-#else
-#define DPRINTF(fmt, ...) \
-    do { } while (0)
-#endif
+#include "trace.h"
 
 /* the page in cache will not be replaced in two cycles */
 #define CACHED_PAGE_LIFETIME 2
@@ -75,7 +68,7 @@ PageCache *cache_init(int64_t new_size, size_t page_size, Error **errp)
     cache->num_items = 0;
     cache->max_num_items = num_pages;
 
-    DPRINTF("Setting cache buckets to %" PRId64 "\n", cache->max_num_items);
+    trace_migration_pagecache_init(cache->max_num_items);
 
     /* We prefer not to abort if there is no memory */
     cache->page_cache = g_try_malloc((cache->max_num_items) *
@@ -169,7 +162,7 @@ int cache_insert(PageCache *cache, uint64_t addr, const uint8_t *pdata,
     if (!it->it_data) {
         it->it_data = g_try_malloc(cache->page_size);
         if (!it->it_data) {
-            DPRINTF("Error allocating page\n");
+            trace_migration_pagecache_insert();
             return -1;
         }
         cache->num_items++;
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index 0a2f88a87d..d3bb3a744b 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -403,7 +403,7 @@ bool postcopy_ram_supported_by_host(MigrationIncomingState *mis)
                      strerror(errno));
         goto out;
     }
-    g_assert(((size_t)testarea & (pagesize-1)) == 0);
+    g_assert(((size_t)testarea & (pagesize - 1)) == 0);
 
     reg_struct.range.start = (uintptr_t)testarea;
     reg_struct.range.len = pagesize;
@@ -684,7 +684,7 @@ int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
                                         qemu_ram_get_idstr(rb), rb_offset);
         return postcopy_wake_shared(pcfd, client_addr, rb);
     }
-    migrate_send_rp_req_pages(mis, rb, aligned_rbo);
+    migrate_send_rp_req_pages(mis, rb, aligned_rbo, client_addr);
     return 0;
 }
 
@@ -979,7 +979,8 @@ retry:
              * Send the request to the source - we want to request one
              * of our host page sizes (which is >= TPS)
              */
-            ret = migrate_send_rp_req_pages(mis, rb, rb_offset);
+            ret = migrate_send_rp_req_pages(mis, rb, rb_offset,
+                                            msg.arg.pagefault.address);
             if (ret) {
                 /* May be network failure, try to wait for recovery */
                 if (ret == -EIO && postcopy_pause_fault_thread(mis)) {
@@ -1128,10 +1129,12 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis)
     return 0;
 }
 
-static int qemu_ufd_copy_ioctl(int userfault_fd, void *host_addr,
+static int qemu_ufd_copy_ioctl(MigrationIncomingState *mis, void *host_addr,
                                void *from_addr, uint64_t pagesize, RAMBlock *rb)
 {
+    int userfault_fd = mis->userfault_fd;
     int ret;
+
     if (from_addr) {
         struct uffdio_copy copy_struct;
         copy_struct.dst = (uint64_t)(uintptr_t)host_addr;
@@ -1147,10 +1150,20 @@ static int qemu_ufd_copy_ioctl(int userfault_fd, void *host_addr,
         ret = ioctl(userfault_fd, UFFDIO_ZEROPAGE, &zero_struct);
     }
     if (!ret) {
+        qemu_mutex_lock(&mis->page_request_mutex);
         ramblock_recv_bitmap_set_range(rb, host_addr,
                                        pagesize / qemu_target_page_size());
+        /*
+         * If this page resolves a page fault for a previous recorded faulted
+         * address, take a special note to maintain the requested page list.
+         */
+        if (g_tree_lookup(mis->page_requested, host_addr)) {
+            g_tree_remove(mis->page_requested, host_addr);
+            mis->page_requested_count--;
+            trace_postcopy_page_req_del(host_addr, mis->page_requested_count);
+        }
+        qemu_mutex_unlock(&mis->page_request_mutex);
         mark_postcopy_blocktime_end((uintptr_t)host_addr);
-
     }
     return ret;
 }
@@ -1185,7 +1198,7 @@ int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
      * which would be slightly cheaper, but we'd have to be careful
      * of the order of updating our page state.
      */
-    if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, from, pagesize, rb)) {
+    if (qemu_ufd_copy_ioctl(mis, host, from, pagesize, rb)) {
         int e = errno;
         error_report("%s: %s copy host: %p from: %p (size: %zd)",
                      __func__, strerror(e), host, from, pagesize);
@@ -1212,7 +1225,7 @@ int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
      * but it's not available for everything (e.g. hugetlbpages)
      */
     if (qemu_ram_is_uf_zeroable(rb)) {
-        if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, NULL, pagesize, rb)) {
+        if (qemu_ufd_copy_ioctl(mis, host, NULL, pagesize, rb)) {
             int e = errno;
             error_report("%s: %s zero host: %p",
                          __func__, strerror(e), host);
diff --git a/migration/ram.c b/migration/ram.c
index 433489d633..2da2b622ab 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -101,14 +101,16 @@ static struct {
 
 static void XBZRLE_cache_lock(void)
 {
-    if (migrate_use_xbzrle())
+    if (migrate_use_xbzrle()) {
         qemu_mutex_lock(&XBZRLE.lock);
+    }
 }
 
 static void XBZRLE_cache_unlock(void)
 {
-    if (migrate_use_xbzrle())
+    if (migrate_use_xbzrle()) {
         qemu_mutex_unlock(&XBZRLE.lock);
+    }
 }
 
 /**
@@ -1563,7 +1565,7 @@ int ram_save_queue_pages(const char *rbname, ram_addr_t start, ram_addr_t len)
         rs->last_req_rb = ramblock;
     }
     trace_ram_save_queue_pages(ramblock->idstr, start, len);
-    if (start+len > ramblock->used_length) {
+    if (start + len > ramblock->used_length) {
         error_report("%s request overrun start=" RAM_ADDR_FMT " len="
                      RAM_ADDR_FMT " blocklen=" RAM_ADDR_FMT,
                      __func__, start, len, ramblock->used_length);
@@ -2741,7 +2743,7 @@ static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host)
  */
 static inline RAMBlock *ram_block_from_stream(QEMUFile *f, int flags)
 {
-    static RAMBlock *block = NULL;
+    static RAMBlock *block;
     char id[256];
     uint8_t len;
 
@@ -3298,7 +3300,7 @@ static int ram_load_postcopy(QEMUFile *f)
             multifd_recv_sync_main();
             break;
         default:
-            error_report("Unknown combination of migration flags: %#x"
+            error_report("Unknown combination of migration flags: 0x%x"
                          " (postcopy mode)", flags);
             ret = -EINVAL;
             break;
@@ -3576,7 +3578,7 @@ static int ram_load_precopy(QEMUFile *f)
             if (flags & RAM_SAVE_FLAG_HOOK) {
                 ram_control_load_hook(f, RAM_CONTROL_HOOK, NULL);
             } else {
-                error_report("Unknown combination of migration flags: %#x",
+                error_report("Unknown combination of migration flags: 0x%x",
                              flags);
                 ret = -EINVAL;
             }
diff --git a/migration/rdma.c b/migration/rdma.c
index 0340841fad..00eac34232 100644
--- a/migration/rdma.c
+++ b/migration/rdma.c
@@ -273,7 +273,8 @@ static uint64_t htonll(uint64_t v)
     return u.llv;
 }
 
-static uint64_t ntohll(uint64_t v) {
+static uint64_t ntohll(uint64_t v)
+{
     union { uint32_t lv[2]; uint64_t llv; } u;
     u.llv = v;
     return ((uint64_t)ntohl(u.lv[0]) << 32) | (uint64_t) ntohl(u.lv[1]);
@@ -854,7 +855,7 @@ static int qemu_rdma_broken_ipv6_kernel(struct ibv_context *verbs, Error **errp)
      */
     if (!verbs) {
         int num_devices, x;
-        struct ibv_device ** dev_list = ibv_get_device_list(&num_devices);
+        struct ibv_device **dev_list = ibv_get_device_list(&num_devices);
         bool roce_found = false;
         bool ib_found = false;
 
@@ -1288,7 +1289,7 @@ const char *print_wrid(int wrid)
  * workload information or LRU information is available, do not attempt to use
  * this feature except for basic testing.
  */
-//#define RDMA_UNREGISTRATION_EXAMPLE
+/* #define RDMA_UNREGISTRATION_EXAMPLE */
 
 /*
  * Perform a non-optimized memory unregistration after every transfer
diff --git a/migration/savevm.c b/migration/savevm.c
index ff33e210eb..21ccba9fb3 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -63,7 +63,7 @@
 #include "qemu/bitmap.h"
 #include "net/announce.h"
 
-const unsigned int postcopy_ram_discard_version = 0;
+const unsigned int postcopy_ram_discard_version;
 
 /* Subcommands for QEMU_VM_COMMAND */
 enum qemu_vm_cmd {
@@ -520,7 +520,7 @@ static const VMStateDescription vmstate_configuration = {
         VMSTATE_VBUFFER_ALLOC_UINT32(name, SaveState, 0, NULL, len),
         VMSTATE_END_OF_LIST()
     },
-    .subsections = (const VMStateDescription*[]) {
+    .subsections = (const VMStateDescription *[]) {
         &vmstate_target_page_bits,
         &vmstate_capabilites,
         &vmstate_uuid,
@@ -2010,6 +2010,49 @@ static int loadvm_postcopy_handle_run(MigrationIncomingState *mis)
     return LOADVM_QUIT;
 }
 
+/* We must be with page_request_mutex held */
+static gboolean postcopy_sync_page_req(gpointer key, gpointer value,
+                                       gpointer data)
+{
+    MigrationIncomingState *mis = data;
+    void *host_addr = (void *) key;
+    ram_addr_t rb_offset;
+    RAMBlock *rb;
+    int ret;
+
+    rb = qemu_ram_block_from_host(host_addr, true, &rb_offset);
+    if (!rb) {
+        /*
+         * This should _never_ happen.  However be nice for a migrating VM to
+         * not crash/assert.  Post an error (note: intended to not use *_once
+         * because we do want to see all the illegal addresses; and this can
+         * never be triggered by the guest so we're safe) and move on next.
+         */
+        error_report("%s: illegal host addr %p", __func__, host_addr);
+        /* Try the next entry */
+        return FALSE;
+    }
+
+    ret = migrate_send_rp_message_req_pages(mis, rb, rb_offset);
+    if (ret) {
+        /* Please refer to above comment. */
+        error_report("%s: send rp message failed for addr %p",
+                     __func__, host_addr);
+        return FALSE;
+    }
+
+    trace_postcopy_page_req_sync(host_addr);
+
+    return FALSE;
+}
+
+static void migrate_send_rp_req_pages_pending(MigrationIncomingState *mis)
+{
+    WITH_QEMU_LOCK_GUARD(&mis->page_request_mutex) {
+        g_tree_foreach(mis->page_requested, postcopy_sync_page_req, mis);
+    }
+}
+
 static int loadvm_postcopy_handle_resume(MigrationIncomingState *mis)
 {
     if (mis->state != MIGRATION_STATUS_POSTCOPY_RECOVER) {
@@ -2032,6 +2075,20 @@ static int loadvm_postcopy_handle_resume(MigrationIncomingState *mis)
     /* Tell source that "we are ready" */
     migrate_send_rp_resume_ack(mis, MIGRATION_RESUME_ACK_VALUE);
 
+    /*
+     * After a postcopy recovery, the source should have lost the postcopy
+     * queue, or potentially the requested pages could have been lost during
+     * the network down phase.  Let's re-sync with the source VM by re-sending
+     * all the pending pages that we eagerly need, so these threads won't get
+     * blocked too long due to the recovery.
+     *
+     * Without this procedure, the faulted destination VM threads (waiting for
+     * page requests right before the postcopy is interrupted) can keep hanging
+     * until the pages are sent by the source during the background copying of
+     * pages, or another thread faulted on the same address accidentally.
+     */
+    migrate_send_rp_req_pages_pending(mis);
+
     return 0;
 }
 
diff --git a/migration/trace-events b/migration/trace-events
index 338f38b3dd..75de5004ac 100644
--- a/migration/trace-events
+++ b/migration/trace-events
@@ -49,6 +49,7 @@ vmstate_save(const char *idstr, const char *vmsd_name) "%s, %s"
 vmstate_load(const char *idstr, const char *vmsd_name) "%s, %s"
 postcopy_pause_incoming(void) ""
 postcopy_pause_incoming_continued(void) ""
+postcopy_page_req_sync(void *host_addr) "sync page req %p"
 
 # vmstate.c
 vmstate_load_field_error(const char *field, int ret) "field \"%s\" load failed, ret = %d"
@@ -162,6 +163,7 @@ postcopy_pause_return_path(void) ""
 postcopy_pause_return_path_continued(void) ""
 postcopy_pause_continued(void) ""
 postcopy_start_set_run(void) ""
+postcopy_page_req_add(void *addr, int count) "new page req %p total %d"
 source_return_path_thread_bad_end(void) ""
 source_return_path_thread_end(void) ""
 source_return_path_thread_entry(void) ""
@@ -272,6 +274,7 @@ postcopy_ram_incoming_cleanup_blocktime(uint64_t total) "total blocktime %" PRIu
 postcopy_request_shared_page(const char *sharer, const char *rb, uint64_t rb_offset) "for %s in %s offset 0x%"PRIx64
 postcopy_request_shared_page_present(const char *sharer, const char *rb, uint64_t rb_offset) "%s already %s offset 0x%"PRIx64
 postcopy_wake_shared(uint64_t client_addr, const char *rb) "at 0x%"PRIx64" in %s"
+postcopy_page_req_del(void *addr, int count) "resolved page req %p total %d"
 
 get_mem_fault_cpu_index(int cpu, uint32_t pid) "cpu: %d, pid: %u"
 
@@ -325,3 +328,16 @@ get_ramblock_vfn_hash(const char *idstr, uint64_t vfn, uint32_t crc) "ramblock n
 calc_page_dirty_rate(const char *idstr, uint32_t new_crc, uint32_t old_crc) "ramblock name: %s, new crc: %" PRIu32 ", old crc: %" PRIu32
 skip_sample_ramblock(const char *idstr, uint64_t ramblock_size) "ramblock name: %s, ramblock size: %" PRIu64
 find_page_matched(const char *idstr) "ramblock %s addr or size changed"
+
+# block.c
+migration_block_init_shared(const char *blk_device_name) "Start migration for %s with shared base image"
+migration_block_init_full(const char *blk_device_name) "Start full migration for %s"
+migration_block_save_device_dirty(int64_t sector) "Error reading sector %" PRId64
+migration_block_flush_blks(const char *action, int submitted, int read_done, int transferred) "%s submitted %d read_done %d transferred %d"
+migration_block_save(const char *mig_stage, int submitted, int transferred) "Enter save live %s submitted %d transferred %d"
+migration_block_save_complete(void) "Block migration completed"
+migration_block_save_pending(uint64_t pending) "Enter save live pending  %" PRIu64
+
+# page_cache.c
+migration_pagecache_init(int64_t max_num_items) "Setting cache buckets to %" PRId64
+migration_pagecache_insert(void) "Error allocating page"
diff --git a/migration/vmstate-types.c b/migration/vmstate-types.c
index 35e784c9d9..e22d41d73d 100644
--- a/migration/vmstate-types.c
+++ b/migration/vmstate-types.c
@@ -420,32 +420,6 @@ const VMStateInfo vmstate_info_uint16_equal = {
     .put  = put_uint16,
 };
 
-/* floating point */
-
-static int get_float64(QEMUFile *f, void *pv, size_t size,
-                       const VMStateField *field)
-{
-    float64 *v = pv;
-
-    *v = make_float64(qemu_get_be64(f));
-    return 0;
-}
-
-static int put_float64(QEMUFile *f, void *pv, size_t size,
-                       const VMStateField *field, QJSON *vmdesc)
-{
-    uint64_t *v = pv;
-
-    qemu_put_be64(f, float64_val(*v));
-    return 0;
-}
-
-const VMStateInfo vmstate_info_float64 = {
-    .name = "float64",
-    .get  = get_float64,
-    .put  = put_float64,
-};
-
 /* CPU_DoubleU type */
 
 static int get_cpudouble(QEMUFile *f, void *pv, size_t size,
diff --git a/migration/vmstate.c b/migration/vmstate.c
index bafa890384..e9d2aef66b 100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c
@@ -32,13 +32,13 @@ static int vmstate_n_elems(void *opaque, const VMStateField *field)
     if (field->flags & VMS_ARRAY) {
         n_elems = field->num;
     } else if (field->flags & VMS_VARRAY_INT32) {
-        n_elems = *(int32_t *)(opaque+field->num_offset);
+        n_elems = *(int32_t *)(opaque + field->num_offset);
     } else if (field->flags & VMS_VARRAY_UINT32) {
-        n_elems = *(uint32_t *)(opaque+field->num_offset);
+        n_elems = *(uint32_t *)(opaque + field->num_offset);
     } else if (field->flags & VMS_VARRAY_UINT16) {
-        n_elems = *(uint16_t *)(opaque+field->num_offset);
+        n_elems = *(uint16_t *)(opaque + field->num_offset);
     } else if (field->flags & VMS_VARRAY_UINT8) {
-        n_elems = *(uint8_t *)(opaque+field->num_offset);
+        n_elems = *(uint8_t *)(opaque + field->num_offset);
     }
 
     if (field->flags & VMS_MULTIPLY_ELEMENTS) {
@@ -54,7 +54,7 @@ static int vmstate_size(void *opaque, const VMStateField *field)
     int size = field->size;
 
     if (field->flags & VMS_VBUFFER) {
-        size = *(int32_t *)(opaque+field->size_offset);
+        size = *(int32_t *)(opaque + field->size_offset);
         if (field->flags & VMS_MULTIPLY) {
             size *= field->size;
         }
diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
index f410ec5996..f2142fbd3c 100644
--- a/tests/qtest/migration-test.c
+++ b/tests/qtest/migration-test.c
@@ -464,6 +464,10 @@ static void migrate_postcopy_start(QTestState *from, QTestState *to)
 }
 
 typedef struct {
+    /*
+     * QTEST_LOG=1 may override this.  When QTEST_LOG=1, we always dump errors
+     * unconditionally, because it means the user would like to be verbose.
+     */
     bool hide_stderr;
     bool use_shmem;
     /* only launch the target process */
@@ -557,7 +561,7 @@ static int test_migrate_start(QTestState **from, QTestState **to,
 
     g_free(bootpath);
 
-    if (args->hide_stderr) {
+    if (!getenv("QTEST_LOG") && args->hide_stderr) {
         ignore_stderr = "2>/dev/null";
     } else {
         ignore_stderr = "";