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Re: [PATCH v3 2/8] migration/savevm: Prepare vmdesc json writer in qemu_
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH v3 2/8] migration/savevm: Prepare vmdesc json writer in qemu_savevm_state_setup() |
Date: |
Thu, 12 Jan 2023 17:43:40 +0000 |
User-agent: |
Mutt/2.2.9 (2022-11-12) |
* David Hildenbrand (david@redhat.com) wrote:
> ... and store it in the migration state. This is a preparation for
> storing selected vmds's already in qemu_savevm_state_setup().
>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> migration/migration.c | 4 ++++
> migration/migration.h | 4 ++++
> migration/savevm.c | 18 ++++++++++++------
> 3 files changed, 20 insertions(+), 6 deletions(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index 52b5d39244..1d33a7efa0 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -2170,6 +2170,9 @@ void migrate_init(MigrationState *s)
> s->vm_was_running = false;
> s->iteration_initial_bytes = 0;
> s->threshold_size = 0;
> +
> + json_writer_free(s->vmdesc);
> + s->vmdesc = NULL;
> }
>
> int migrate_add_blocker_internal(Error *reason, Error **errp)
> @@ -4445,6 +4448,7 @@ static void migration_instance_finalize(Object *obj)
> qemu_sem_destroy(&ms->rp_state.rp_sem);
> qemu_sem_destroy(&ms->postcopy_qemufile_src_sem);
> error_free(ms->error);
> + json_writer_free(ms->vmdesc);
I'm not sure this is happening when you think it is.
I *think* this only happens when qemu quits....
> }
>
> static void migration_instance_init(Object *obj)
> diff --git a/migration/migration.h b/migration/migration.h
> index ae4ffd3454..66511ce532 100644
> --- a/migration/migration.h
> +++ b/migration/migration.h
> @@ -17,6 +17,7 @@
> #include "exec/cpu-common.h"
> #include "hw/qdev-core.h"
> #include "qapi/qapi-types-migration.h"
> +#include "qapi/qmp/json-writer.h"
> #include "qemu/thread.h"
> #include "qemu/coroutine_int.h"
> #include "io/channel.h"
> @@ -366,6 +367,9 @@ struct MigrationState {
> * This save hostname when out-going migration starts
> */
> char *hostname;
> +
> + /* QEMU_VM_VMDESCRIPTION content filled for all non-iterable devices. */
> + JSONWriter *vmdesc;
> };
>
> void migrate_set_state(int *state, int old_state, int new_state);
> diff --git a/migration/savevm.c b/migration/savevm.c
> index d8830297e4..ff2b8d0064 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -42,7 +42,6 @@
> #include "postcopy-ram.h"
> #include "qapi/error.h"
> #include "qapi/qapi-commands-migration.h"
> -#include "qapi/qmp/json-writer.h"
> #include "qapi/clone-visitor.h"
> #include "qapi/qapi-builtin-visit.h"
> #include "qapi/qmp/qerror.h"
> @@ -1189,10 +1188,16 @@ bool qemu_savevm_state_guest_unplug_pending(void)
>
> void qemu_savevm_state_setup(QEMUFile *f)
> {
> + MigrationState *ms = migrate_get_current();
> SaveStateEntry *se;
> Error *local_err = NULL;
> int ret;
>
> + ms->vmdesc = json_writer_new(false);
> + json_writer_start_object(ms->vmdesc, NULL);
> + json_writer_int64(ms->vmdesc, "page_size", qemu_target_page_size());
> + json_writer_start_array(ms->vmdesc, "devices");
> +
> trace_savevm_state_setup();
> QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
> if (!se->ops || !se->ops->save_setup) {
> @@ -1390,15 +1395,12 @@ int
> qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
> bool in_postcopy,
> bool inactivate_disks)
> {
> - g_autoptr(JSONWriter) vmdesc = NULL;
> + MigrationState *ms = migrate_get_current();
> + JSONWriter *vmdesc = ms->vmdesc;
> int vmdesc_len;
> SaveStateEntry *se;
> int ret;
>
> - vmdesc = json_writer_new(false);
> - json_writer_start_object(vmdesc, NULL);
> - json_writer_int64(vmdesc, "page_size", qemu_target_page_size());
> - json_writer_start_array(vmdesc, "devices");
> QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
> ret = vmstate_save(f, se, vmdesc);
> if (ret) {
> @@ -1433,6 +1435,10 @@ int
> qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
> qemu_put_buffer(f, (uint8_t *)json_writer_get(vmdesc), vmdesc_len);
> }
>
> + /* Free it now to detect any inconsistencies. */
> + json_writer_free(vmdesc);
> + ms->vmdesc = NULL;
and this only happens when this succesfully exits; so if this errors
out, and then you retry an outwards migration, I think you've leaked a
writer.
Dave
> return 0;
> }
>
> --
> 2.39.0
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
[PATCH v3 2/8] migration/savevm: Prepare vmdesc json writer in qemu_savevm_state_setup(), David Hildenbrand, 2023/01/12
- Re: [PATCH v3 2/8] migration/savevm: Prepare vmdesc json writer in qemu_savevm_state_setup(),
Dr. David Alan Gilbert <=
- Re: [PATCH v3 2/8] migration/savevm: Prepare vmdesc json writer in qemu_savevm_state_setup(), David Hildenbrand, 2023/01/12
- Re: [PATCH v3 2/8] migration/savevm: Prepare vmdesc json writer in qemu_savevm_state_setup(), Dr. David Alan Gilbert, 2023/01/12
- Re: [PATCH v3 2/8] migration/savevm: Prepare vmdesc json writer in qemu_savevm_state_setup(), Peter Xu, 2023/01/12
- Re: [PATCH v3 2/8] migration/savevm: Prepare vmdesc json writer in qemu_savevm_state_setup(), David Hildenbrand, 2023/01/13
- Re: [PATCH v3 2/8] migration/savevm: Prepare vmdesc json writer in qemu_savevm_state_setup(), David Hildenbrand, 2023/01/13
[PATCH v3 3/8] migration/savevm: Allow immutable device state to be migrated early (i.e., before RAM), David Hildenbrand, 2023/01/12