migration/migration.h | 1 + migration/migration.c | 15 ++++++++++++++- migration/rdma.c | 8 +++----- migration/tls.c | 4 ++-- 4 files changed, 20 insertions(+), 8 deletions(-)
Introduce a helper to show if we want to enable return path.
We used to imply that for postcopy-ram, that's not normally how we add cap
dependencies, however it has been like it for years. Add some comment and
stick with it.
Signed-off-by: Peter Xu <peterx@redhat.com>
---
migration/migration.h | 1 +
migration/migration.c | 15 ++++++++++++++-
migration/rdma.c | 8 +++-----
migration/tls.c | 4 ++--
4 files changed, 20 insertions(+), 8 deletions(-)
diff --git a/migration/migration.h b/migration/migration.h
index ccc4e536a5..32c2e70205 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -605,5 +605,6 @@ void migration_bitmap_sync_precopy(bool last_stage);
/* migration/block-dirty-bitmap.c */
void dirty_bitmap_mig_init(void);
bool should_send_vmdesc(void);
+bool migrate_use_return_path(void);
#endif
diff --git a/migration/migration.c b/migration/migration.c
index 1bcde301f7..f550485ea5 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -109,6 +109,19 @@ static bool close_return_path_on_source(MigrationState *s);
static void migration_completion_end(MigrationState *s);
static void migrate_hup_delete(MigrationState *s);
+/*
+ * Postcopy-ram will imply return path.
+ *
+ * Normally we don't describe capability dependencies like this; we could
+ * have failed the migration request if postcopy-ram is selected withour
+ * return-path. Said that, we had this as part of postcopy-ram capability
+ * ABI for years.. let's stick with it.
+ */
+bool migrate_use_return_path(void)
+{
+ return migrate_postcopy_ram() || migrate_return_path();
+}
+
static void migration_downtime_start(MigrationState *s)
{
trace_vmstate_downtime_checkpoint("src-downtime-start");
@@ -4067,7 +4080,7 @@ void migration_connect(MigrationState *s, Error *error_in)
* precopy, only if user specified "return-path" capability would
* QEMU uses the return path.
*/
- if (migrate_postcopy_ram() || migrate_return_path()) {
+ if (migrate_use_return_path()) {
open_return_path_on_source(s);
}
diff --git a/migration/rdma.c b/migration/rdma.c
index cced173379..a55c80908c 100644
--- a/migration/rdma.c
+++ b/migration/rdma.c
@@ -3186,8 +3186,7 @@ static int qemu_rdma_accept(RDMAContext *rdma)
* initialize the RDMAContext for return path for postcopy after first
* connection request reached.
*/
- if ((migrate_postcopy() || migrate_return_path())
- && !rdma->is_return_path) {
+ if (migrate_use_return_path() && !rdma->is_return_path) {
rdma_return_path = qemu_rdma_data_init(isock, NULL);
if (rdma_return_path == NULL) {
rdma_ack_cm_event(cm_event);
@@ -3265,8 +3264,7 @@ static int qemu_rdma_accept(RDMAContext *rdma)
}
/* Accept the second connection request for return path */
- if ((migrate_postcopy() || migrate_return_path())
- && !rdma->is_return_path) {
+ if (migrate_use_return_path() && !rdma->is_return_path) {
qemu_set_fd_handler(rdma->channel->fd, rdma_accept_incoming_migration,
NULL,
(void *)(intptr_t)rdma->return_path);
@@ -3967,7 +3965,7 @@ void rdma_start_outgoing_migration(void *opaque,
}
/* RDMA postcopy need a separate queue pair for return path */
- if (migrate_postcopy() || migrate_return_path()) {
+ if (migrate_use_return_path()) {
rdma_return_path = qemu_rdma_data_init(host_port, errp);
if (rdma_return_path == NULL) {
diff --git a/migration/tls.c b/migration/tls.c
index 56b5d1cc90..7fb49ddd82 100644
--- a/migration/tls.c
+++ b/migration/tls.c
@@ -90,7 +90,7 @@ void migration_tls_channel_process_incoming(MigrationState *s,
trace_migration_tls_incoming_handshake_start();
qio_channel_set_name(QIO_CHANNEL(tioc), "migration-tls-incoming");
- if (migrate_postcopy_ram() || migrate_return_path()) {
+ if (migrate_use_return_path()) {
qio_channel_set_feature(QIO_CHANNEL(tioc),
QIO_CHANNEL_FEATURE_CONCURRENT_IO);
}
@@ -154,7 +154,7 @@ void migration_tls_channel_connect(MigrationState *s,
trace_migration_tls_outgoing_handshake_start(hostname);
qio_channel_set_name(QIO_CHANNEL(tioc), "migration-tls-outgoing");
- if (migrate_postcopy_ram() || migrate_return_path()) {
+ if (migrate_use_return_path()) {
qio_channel_set_feature(QIO_CHANNEL(tioc),
QIO_CHANNEL_FEATURE_CONCURRENT_IO);
}
--
2.50.1On Fri, 23 Jan 2026 at 03:41, Peter Xu <peterx@redhat.com> wrote:
> Introduce a helper to show if we want to enable return path.
* return path -> the return path
> We used to imply that for postcopy-ram, that's not normally how we add cap
> dependencies, however it has been like it for years. Add some comment and
> stick with it.
/* This reads more suitable for cover-letter. */ Maybe - Postcopy
requires and enables the return path connection, add due comments for
it.
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> migration/migration.h | 1 +
> migration/migration.c | 15 ++++++++++++++-
> migration/rdma.c | 8 +++-----
> migration/tls.c | 4 ++--
> 4 files changed, 20 insertions(+), 8 deletions(-)
>
> diff --git a/migration/migration.h b/migration/migration.h
> index ccc4e536a5..32c2e70205 100644
> --- a/migration/migration.h
> +++ b/migration/migration.h
> @@ -605,5 +605,6 @@ void migration_bitmap_sync_precopy(bool last_stage);
> /* migration/block-dirty-bitmap.c */
> void dirty_bitmap_mig_init(void);
> bool should_send_vmdesc(void);
> +bool migrate_use_return_path(void);
>
> #endif
> diff --git a/migration/migration.c b/migration/migration.c
> index 1bcde301f7..f550485ea5 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -109,6 +109,19 @@ static bool close_return_path_on_source(MigrationState *s);
> static void migration_completion_end(MigrationState *s);
> static void migrate_hup_delete(MigrationState *s);
>
> +/*
> + * Postcopy-ram will imply return path.
* Postcopy-ram requires and enables the return path connection.
> + * Normally we don't describe capability dependencies like this; we could
> + * have failed the migration request if postcopy-ram is selected withour
> + * return-path. Said that, we had this as part of postcopy-ram capability
> + * ABI for years.. let's stick with it.
> + */
* withour -> without the
> +bool migrate_use_return_path(void)
> +{
> + return migrate_postcopy_ram() || migrate_return_path();
> +}
> +
* It would have been nicer if we could include '&&
!rdma->is_return_path' here, but that does not seem doable. Is '&&
!rdma->is_return_path' check really required?
> static void migration_downtime_start(MigrationState *s)
> {
> trace_vmstate_downtime_checkpoint("src-downtime-start");
> @@ -4067,7 +4080,7 @@ void migration_connect(MigrationState *s, Error *error_in)
> * precopy, only if user specified "return-path" capability would
> * QEMU uses the return path.
> */
> - if (migrate_postcopy_ram() || migrate_return_path()) {
> + if (migrate_use_return_path()) {
> open_return_path_on_source(s);
> }
>
> diff --git a/migration/rdma.c b/migration/rdma.c
> index cced173379..a55c80908c 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -3186,8 +3186,7 @@ static int qemu_rdma_accept(RDMAContext *rdma)
> * initialize the RDMAContext for return path for postcopy after first
> * connection request reached.
> */
> - if ((migrate_postcopy() || migrate_return_path())
> - && !rdma->is_return_path) {
> + if (migrate_use_return_path() && !rdma->is_return_path) {
> rdma_return_path = qemu_rdma_data_init(isock, NULL);
* Here we check && !rdma->is_return_path
> /* RDMA postcopy need a separate queue pair for return path */
> - if (migrate_postcopy() || migrate_return_path()) {
> + if (migrate_use_return_path()) {
> rdma_return_path = qemu_rdma_data_init(host_port, errp);
* Here we don't check '&& !rdma->is_return_path' ...?
> if (rdma_return_path == NULL) {
> diff --git a/migration/tls.c b/migration/tls.c
> index 56b5d1cc90..7fb49ddd82 100644
> --- a/migration/tls.c
> +++ b/migration/tls.c
> @@ -90,7 +90,7 @@ void migration_tls_channel_process_incoming(MigrationState *s,
>
> trace_migration_tls_incoming_handshake_start();
> qio_channel_set_name(QIO_CHANNEL(tioc), "migration-tls-incoming");
> - if (migrate_postcopy_ram() || migrate_return_path()) {
> + if (migrate_use_return_path()) {
> qio_channel_set_feature(QIO_CHANNEL(tioc),
> QIO_CHANNEL_FEATURE_CONCURRENT_IO);
> }
> @@ -154,7 +154,7 @@ void migration_tls_channel_connect(MigrationState *s,
> trace_migration_tls_outgoing_handshake_start(hostname);
> qio_channel_set_name(QIO_CHANNEL(tioc), "migration-tls-outgoing");
>
> - if (migrate_postcopy_ram() || migrate_return_path()) {
> + if (migrate_use_return_path()) {
> qio_channel_set_feature(QIO_CHANNEL(tioc),
> QIO_CHANNEL_FEATURE_CONCURRENT_IO);
> }
> --
* Change looks okay. /* The !rdma->is_return_path check is a little
confusing. */
Reviewed-by: Prasad Pandit <pjp@fedoraproject.org>
Thank you.
---
- Prasad
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