migration: cpr-transfer save and load

Add functions to create a QEMUFile based on a unix URI, for saving or
loading, for use by cpr-transfer mode to preserve CPR state.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1736967650-129648-16-git-send-email-steven.sistare@oracle.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>

include/migration/cpr.h

@@ -22,4 +22,7 @@ int cpr_state_load(MigrationChannel *channel, Error **errp);
 void cpr_state_close(void);
 struct QIOChannel *cpr_state_ioc(void);
 
+QEMUFile *cpr_transfer_output(MigrationChannel *channel, Error **errp);
+QEMUFile *cpr_transfer_input(MigrationChannel *channel, Error **errp);
+
 #endif

migration/cpr-transfer.c

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2022, 2024 Oracle and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "io/channel-file.h"
+#include "io/channel-socket.h"
+#include "io/net-listener.h"
+#include "migration/cpr.h"
+#include "migration/migration.h"
+#include "migration/savevm.h"
+#include "migration/qemu-file.h"
+#include "migration/vmstate.h"
+#include "trace.h"
+
+QEMUFile *cpr_transfer_output(MigrationChannel *channel, Error **errp)
+{
+    MigrationAddress *addr = channel->addr;
+
+    if (addr->transport == MIGRATION_ADDRESS_TYPE_SOCKET &&
+        addr->u.socket.type == SOCKET_ADDRESS_TYPE_UNIX) {
+
+        g_autoptr(QIOChannelSocket) sioc = qio_channel_socket_new();
+        QIOChannel *ioc = QIO_CHANNEL(sioc);
+        SocketAddress *saddr = &addr->u.socket;
+
+        if (qio_channel_socket_connect_sync(sioc, saddr, errp) < 0) {
+            return NULL;
+        }
+        trace_cpr_transfer_output(addr->u.socket.u.q_unix.path);
+        qio_channel_set_name(ioc, "cpr-out");
+        return qemu_file_new_output(ioc);
+
+    } else {
+        error_setg(errp, "bad cpr channel address; must be unix");
+        return NULL;
+    }
+}
+
+QEMUFile *cpr_transfer_input(MigrationChannel *channel, Error **errp)
+{
+    MigrationAddress *addr = channel->addr;
+
+    if (addr->transport == MIGRATION_ADDRESS_TYPE_SOCKET &&
+        addr->u.socket.type == SOCKET_ADDRESS_TYPE_UNIX) {
+
+        g_autoptr(QIOChannelSocket) sioc = NULL;
+        SocketAddress *saddr = &addr->u.socket;
+        g_autoptr(QIONetListener) listener = qio_net_listener_new();
+        QIOChannel *ioc;
+
+        qio_net_listener_set_name(listener, "cpr-socket-listener");
+        if (qio_net_listener_open_sync(listener, saddr, 1, errp) < 0) {
+            return NULL;
+        }
+
+        sioc = qio_net_listener_wait_client(listener);
+        ioc = QIO_CHANNEL(sioc);
+        trace_cpr_transfer_input(addr->u.socket.u.q_unix.path);
+        qio_channel_set_name(ioc, "cpr-in");
+        return qemu_file_new_input(ioc);
+
+    } else {
+        error_setg(errp, "bad cpr channel socket type; must be unix");
+        return NULL;
+    }
+}

migration/meson.build

@@ -15,6 +15,7 @@ system_ss.add(files(
   'channel.c',
   'channel-block.c',
   'cpr.c',
+  'cpr-transfer.c',
   'cpu-throttle.c',
   'dirtyrate.c',
   'exec.c',

migration/trace-events

@@ -350,6 +350,8 @@ cpr_delete_fd(const char *name, int id) "%s, id %d"
 cpr_find_fd(const char *name, int id, int fd) "%s, id %d returns %d"
 cpr_state_save(const char *mode) "%s mode"
 cpr_state_load(const char *mode) "%s mode"
+cpr_transfer_input(const char *path) "%s"
+cpr_transfer_output(const char *path) "%s"
 
 # block-dirty-bitmap.c
 send_bitmap_header_enter(void) ""