Merge tag 'migration-20240317-pull-request' of https://gitlab.com/peterx/qemu into staging

Migration pull for 9.0-rc0

- Nicholas/Phil's fix on migration corruption / inconsistent for tcg
- Cedric's fix on block migration over n_sectors==0
- Steve's CPR reboot documentation page
- Fabiano's misc fixes on mapped-ram (IOC leak, dup() errors, fd checks, fd
  use race, etc.)

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# gpg:                using EDDSA key B9184DC20CC457DACF7DD1A93B5FCCCDF3ABD706
# gpg:                issuer "peterx@redhat.com"
# gpg: Good signature from "Peter Xu <xzpeter@gmail.com>" [marginal]
# gpg:                 aka "Peter Xu <peterx@redhat.com>" [marginal]
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* tag 'migration-20240317-pull-request' of https://gitlab.com/peterx/qemu:
  migration/multifd: Duplicate the fd for the outgoing_args
  migration/multifd: Ensure we're not given a socket for file migration
  migration: Fix iocs leaks during file and fd migration
  migration: cpr-reboot documentation
  migration: Skip only empty block devices
  physmem: Fix migration dirty bitmap coherency with TCG memory access
  physmem: Factor cpu_physical_memory_dirty_bits_cleared() out
  physmem: Expose tlb_reset_dirty_range_all()
  migration: Fix error handling after dup in file migration
  io: Introduce qio_channel_file_new_dupfd

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

5 files changed, 84 insertions, 54 deletions

diff --git a/migration/block.c b/migration/block.c
index 8c6ebafacc..2b9054889a 100644
--- a/migration/block.c
+++ b/migration/block.c
@@ -402,7 +402,10 @@ static int init_blk_migration(QEMUFile *f)
         }
 
         sectors = bdrv_nb_sectors(bs);
-        if (sectors <= 0) {
+        if (sectors == 0) {
+            continue;
+        }
+        if (sectors < 0) {
             ret = sectors;
             bdrv_next_cleanup(&it);
             goto out;
diff --git a/migration/fd.c b/migration/fd.c
index d4ae72d132..fe0d096abd 100644
--- a/migration/fd.c
+++ b/migration/fd.c
@@ -18,9 +18,11 @@
 #include "qapi/error.h"
 #include "channel.h"
 #include "fd.h"
+#include "file.h"
 #include "migration.h"
 #include "monitor/monitor.h"
 #include "io/channel-file.h"
+#include "io/channel-socket.h"
 #include "io/channel-util.h"
 #include "options.h"
 #include "trace.h"
@@ -47,8 +49,7 @@ void fd_start_outgoing_migration(MigrationState *s, const char *fdname, Error **
 {
     QIOChannel *ioc;
     int fd = monitor_get_fd(monitor_cur(), fdname, errp);
-
-    outgoing_args.fd = -1;
+    int newfd;
 
     if (fd == -1) {
         return;
@@ -61,7 +62,17 @@ void fd_start_outgoing_migration(MigrationState *s, const char *fdname, Error **
         return;
     }
 
-    outgoing_args.fd = fd;
+    /*
+     * This is dup()ed just to avoid referencing an fd that might
+     * be already closed by the iochannel.
+     */
+    newfd = dup(fd);
+    if (newfd == -1) {
+        error_setg_errno(errp, errno, "Could not dup FD %d", fd);
+        object_unref(ioc);
+        return;
+    }
+    outgoing_args.fd = newfd;
 
     qio_channel_set_name(ioc, "migration-fd-outgoing");
     migration_channel_connect(s, ioc, NULL, NULL);
@@ -93,28 +104,20 @@ void fd_start_incoming_migration(const char *fdname, Error **errp)
         return;
     }
 
-    qio_channel_set_name(ioc, "migration-fd-incoming");
-    qio_channel_add_watch_full(ioc, G_IO_IN,
-                               fd_accept_incoming_migration,
-                               NULL, NULL,
-                               g_main_context_get_thread_default());
-
     if (migrate_multifd()) {
-        int channels = migrate_multifd_channels();
-
-        while (channels--) {
-            ioc = QIO_CHANNEL(qio_channel_file_new_fd(dup(fd)));
-
-            if (QIO_CHANNEL_FILE(ioc)->fd == -1) {
-                error_setg(errp, "Failed to duplicate fd %d", fd);
-                return;
-            }
-
-            qio_channel_set_name(ioc, "migration-fd-incoming");
-            qio_channel_add_watch_full(ioc, G_IO_IN,
-                                       fd_accept_incoming_migration,
-                                       NULL, NULL,
-                                       g_main_context_get_thread_default());
+        if (fd_is_socket(fd)) {
+            error_setg(errp,
+                       "Multifd migration to a socket FD is not supported");
+            object_unref(ioc);
+            return;
         }
+
+        file_create_incoming_channels(ioc, errp);
+    } else {
+        qio_channel_set_name(ioc, "migration-fd-incoming");
+        qio_channel_add_watch_full(ioc, G_IO_IN,
+                                   fd_accept_incoming_migration,
+                                   NULL, NULL,
+                                   g_main_context_get_thread_default());
     }
 }
diff --git a/migration/file.c b/migration/file.c
index b0b963e0ce..b6e8ba13f2 100644
--- a/migration/file.c
+++ b/migration/file.c
@@ -15,6 +15,7 @@
 #include "file.h"
 #include "migration.h"
 #include "io/channel-file.h"
+#include "io/channel-socket.h"
 #include "io/channel-util.h"
 #include "options.h"
 #include "trace.h"
@@ -58,12 +59,19 @@ bool file_send_channel_create(gpointer opaque, Error **errp)
     int fd = fd_args_get_fd();
 
     if (fd && fd != -1) {
-        ioc = qio_channel_file_new_fd(dup(fd));
-    } else {
-        ioc = qio_channel_file_new_path(outgoing_args.fname, flags, 0, errp);
-        if (!ioc) {
+        if (fd_is_socket(fd)) {
+            error_setg(errp,
+                       "Multifd migration to a socket FD is not supported");
             goto out;
         }
+
+        ioc = qio_channel_file_new_dupfd(fd, errp);
+    } else {
+        ioc = qio_channel_file_new_path(outgoing_args.fname, flags, 0, errp);
+    }
+
+    if (!ioc) {
+        goto out;
     }
 
     multifd_channel_connect(opaque, QIO_CHANNEL(ioc));
@@ -114,13 +122,46 @@ static gboolean file_accept_incoming_migration(QIOChannel *ioc,
     return G_SOURCE_REMOVE;
 }
 
+void file_create_incoming_channels(QIOChannel *ioc, Error **errp)
+{
+    int i, fd, channels = 1;
+    g_autofree QIOChannel **iocs = NULL;
+
+    if (migrate_multifd()) {
+        channels += migrate_multifd_channels();
+    }
+
+    iocs = g_new0(QIOChannel *, channels);
+    fd = QIO_CHANNEL_FILE(ioc)->fd;
+    iocs[0] = ioc;
+
+    for (i = 1; i < channels; i++) {
+        QIOChannelFile *fioc = qio_channel_file_new_dupfd(fd, errp);
+
+        if (!fioc) {
+            while (i) {
+                object_unref(iocs[--i]);
+            }
+            return;
+        }
+
+        iocs[i] = QIO_CHANNEL(fioc);
+    }
+
+    for (i = 0; i < channels; i++) {
+        qio_channel_set_name(iocs[i], "migration-file-incoming");
+        qio_channel_add_watch_full(iocs[i], G_IO_IN,
+                                   file_accept_incoming_migration,
+                                   NULL, NULL,
+                                   g_main_context_get_thread_default());
+    }
+}
+
 void file_start_incoming_migration(FileMigrationArgs *file_args, Error **errp)
 {
     g_autofree char *filename = g_strdup(file_args->filename);
     QIOChannelFile *fioc = NULL;
     uint64_t offset = file_args->offset;
-    int channels = 1;
-    int i = 0;
 
     trace_migration_file_incoming(filename);
 
@@ -131,29 +172,11 @@ void file_start_incoming_migration(FileMigrationArgs *file_args, Error **errp)
 
     if (offset &&
         qio_channel_io_seek(QIO_CHANNEL(fioc), offset, SEEK_SET, errp) < 0) {
+        object_unref(OBJECT(fioc));
         return;
     }
 
-    if (migrate_multifd()) {
-        channels += migrate_multifd_channels();
-    }
-
-    do {
-        QIOChannel *ioc = QIO_CHANNEL(fioc);
-
-        qio_channel_set_name(ioc, "migration-file-incoming");
-        qio_channel_add_watch_full(ioc, G_IO_IN,
-                                   file_accept_incoming_migration,
-                                   NULL, NULL,
-                                   g_main_context_get_thread_default());
-
-        fioc = qio_channel_file_new_fd(dup(fioc->fd));
-
-        if (!fioc || fioc->fd == -1) {
-            error_setg(errp, "Error creating migration incoming channel");
-            break;
-        }
-    } while (++i < channels);
+    file_create_incoming_channels(QIO_CHANNEL(fioc), errp);
 }
 
 int file_write_ramblock_iov(QIOChannel *ioc, const struct iovec *iov,
diff --git a/migration/file.h b/migration/file.h
index 9f71e87f74..7699c04677 100644
--- a/migration/file.h
+++ b/migration/file.h
@@ -20,6 +20,7 @@ void file_start_outgoing_migration(MigrationState *s,
 int file_parse_offset(char *filespec, uint64_t *offsetp, Error **errp);
 void file_cleanup_outgoing_migration(void);
 bool file_send_channel_create(gpointer opaque, Error **errp);
+void file_create_incoming_channels(QIOChannel *ioc, Error **errp);
 int file_write_ramblock_iov(QIOChannel *ioc, const struct iovec *iov,
                             int niov, RAMBlock *block, Error **errp);
 int multifd_file_recv_data(MultiFDRecvParams *p, Error **errp);
diff --git a/migration/migration.c b/migration/migration.c
index 644e073b7d..f60bd371e3 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -166,9 +166,9 @@ static bool transport_supports_seeking(MigrationAddress *addr)
     }
 
     /*
-     * At this point, the user might not yet have passed the file
-     * descriptor to QEMU, so we cannot know for sure whether it
-     * refers to a plain file or a socket. Let it through anyway.
+     * At this point QEMU has not yet fetched the fd passed in by the
+     * user, so we cannot know for sure whether it refers to a plain
+     * file or a socket. Let it through anyway and check at fd.c.
      */
     if (addr->transport == MIGRATION_ADDRESS_TYPE_SOCKET) {
         return addr->u.socket.type == SOCKET_ADDRESS_TYPE_FD;