Steven Sistare <steven.sist...@oracle.com> writes: > On 5/6/2024 7:34 PM, Fabiano Rosas wrote: >> Steve Sistare <steven.sist...@oracle.com> writes: >> >>> 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); >> >> Can we avoid the QEMUFile? I don't see it being exported from this file. > > It is not exported, but within this file, it is the basis for all read and > write operations, via the existing functions qemu_file_new_input() and > qemu_file_new_output()
Right, that's the easy part, we could just use the QIOChannel directly. But I missed the fact that you also need to interop with the existing code that needs the QEMUFile. Reviewed-by: Fabiano Rosas <faro...@suse.de>