Provide migration_precreate_save for saving precreate vmstate across exec.
Create a memfd, save its value in the environment, and serialize state
to it. Reverse the process in migration_precreate_load.
Signed-off-by: Steve Sistare <steven.sist...@oracle.com>
---
include/migration/misc.h | 5 ++
migration/meson.build | 1 +
migration/precreate.c | 139 +++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 145 insertions(+)
create mode 100644 migration/precreate.c
diff --git a/include/migration/misc.h b/include/migration/misc.h
index c9e200f..cf30351 100644
--- a/include/migration/misc.h
+++ b/include/migration/misc.h
@@ -56,6 +56,11 @@ AnnounceParameters *migrate_announce_params(void);
void dump_vmstate_json_to_file(FILE *out_fp);
+/* migration/precreate.c */
+int migration_precreate_save(Error **errp);
+void migration_precreate_unsave(void);
+int migration_precreate_load(Error **errp);
+
/* migration/migration.c */
void migration_object_init(void);
void migration_shutdown(void);
diff --git a/migration/meson.build b/migration/meson.build
index f76b1ba..50e7cb2 100644
--- a/migration/meson.build
+++ b/migration/meson.build
@@ -26,6 +26,7 @@ system_ss.add(files(
'ram-compress.c',
'options.c',
'postcopy-ram.c',
+ 'precreate.c',
'savevm.c',
'socket.c',
'tls.c',
diff --git a/migration/precreate.c b/migration/precreate.c
new file mode 100644
index 0000000..0bf5e1f
--- /dev/null
+++ b/migration/precreate.c
@@ -0,0 +1,139 @@
+/*
+ * 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 "qemu/cutils.h"
+#include "qemu/memfd.h"
+#include "qapi/error.h"
+#include "io/channel-file.h"
+#include "migration/misc.h"
+#include "migration/qemu-file.h"
+#include "migration/savevm.h"
+
+#define PRECREATE_STATE_NAME "QEMU_PRECREATE_STATE"
+
+static QEMUFile *qemu_file_new_fd_input(int fd, const char *name)
+{
+ g_autoptr(QIOChannelFile) fioc = qio_channel_file_new_fd(fd);
+ QIOChannel *ioc = QIO_CHANNEL(fioc);
+ qio_channel_set_name(ioc, name);
+ return qemu_file_new_input(ioc);
+}
+
+static QEMUFile *qemu_file_new_fd_output(int fd, const char *name)
+{
+ g_autoptr(QIOChannelFile) fioc = qio_channel_file_new_fd(fd);
+ QIOChannel *ioc = QIO_CHANNEL(fioc);
+ qio_channel_set_name(ioc, name);
+ return qemu_file_new_output(ioc);
+}
+
+static int memfd_create_named(const char *name, Error **errp)
+{
+ int mfd;
+ char val[16];
+
+ mfd = memfd_create(name, 0);
+ if (mfd < 0) {
+ error_setg_errno(errp, errno, "memfd_create failed");
+ return -1;
+ }
+
+ /* Remember mfd in environment for post-exec load */
+ qemu_clear_cloexec(mfd);
+ snprintf(val, sizeof(val), "%d", mfd);
+ g_setenv(name, val, 1);
+
+ return mfd;
+}
+
+static int memfd_find_named(const char *name, int *mfd_p, Error **errp)
+{
+ const char *val = g_getenv(name);
+
+ if (!val) {
+ *mfd_p = -1;
+ return 0; /* No memfd was created, not an error */
+ }
+ g_unsetenv(name);
+ if (qemu_strtoi(val, NULL, 10, mfd_p)) {
+ error_setg(errp, "Bad %s env value %s", PRECREATE_STATE_NAME, val);
+ return -1;
+ }
+ lseek(*mfd_p, 0, SEEK_SET);
+ return 0;
+}
+
+static void memfd_delete_named(const char *name)
+{
+ int mfd;
+ const char *val = g_getenv(name);
+
+ if (val) {
+ g_unsetenv(name);
+ if (!qemu_strtoi(val, NULL, 10, &mfd)) {
+ close(mfd);
+ }
+ }
+}
+
+static QEMUFile *qemu_file_new_memfd_output(const char *name, Error **errp)
+{
+ int mfd = memfd_create_named(name, errp);
+
+ if (mfd < 0) {
+ return NULL;
+ }
+
+ return qemu_file_new_fd_output(mfd, name);
+}
+
+static QEMUFile *qemu_file_new_memfd_input(const char *name, Error **errp)
+{
+ int ret, mfd;
+
+ ret = memfd_find_named(name, &mfd, errp);
+ if (ret || mfd < 0) {
+ return NULL;
+ }
+
+ return qemu_file_new_fd_input(mfd, name);
+}
+
+int migration_precreate_save(Error **errp)
+{
+ QEMUFile *f = qemu_file_new_memfd_output(PRECREATE_STATE_NAME, errp);
+
+ if (!f) {
+ return -1;
+ } else if (qemu_savevm_precreate_save(f, errp)) {
+ memfd_delete_named(PRECREATE_STATE_NAME);
+ return -1;
+ } else {
+ /* Do not close f, as mfd must remain open. */
+ return 0;
+ }
+}
+
+void migration_precreate_unsave(void)
+{
+ memfd_delete_named(PRECREATE_STATE_NAME);
+}
+
+int migration_precreate_load(Error **errp)
+{
+ int ret;
+ QEMUFile *f = qemu_file_new_memfd_input(PRECREATE_STATE_NAME, errp);
