Re: [Qemu-devel] [PATCH v2 2/5] migration: create a dedicated connection for rdma return path

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Lidong Chen (jemmy858585@gmail.com) wrote:
> If start a RDMA migration with postcopy enabled, the source qemu
> establish a dedicated connection for return path.
> 
> Signed-off-by: Lidong Chen <lidongchen@tencent.com>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Oops, I should have Reviewed-by rather than Signed-off-by, so:


Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  migration/rdma.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 91 insertions(+), 3 deletions(-)
> 
> diff --git a/migration/rdma.c b/migration/rdma.c
> index a22be43..c745427 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -387,6 +387,10 @@ typedef struct RDMAContext {
>      uint64_t unregistrations[RDMA_SIGNALED_SEND_MAX];
>  
>      GHashTable *blockmap;
> +
> +    /* the RDMAContext for return path */
> +    struct RDMAContext *return_path;
> +    bool is_return_path;
>  } RDMAContext;
>  
>  #define TYPE_QIO_CHANNEL_RDMA "qio-channel-rdma"
> @@ -2329,10 +2333,22 @@ static void qemu_rdma_cleanup(RDMAContext *rdma)
>          rdma_destroy_id(rdma->cm_id);
>          rdma->cm_id = NULL;
>      }
> +
> +    /* the destination side, listen_id and channel is shared */
>      if (rdma->listen_id) {
> -        rdma_destroy_id(rdma->listen_id);
> +        if (!rdma->is_return_path) {
> +            rdma_destroy_id(rdma->listen_id);
> +        }
>          rdma->listen_id = NULL;
> +
> +        if (rdma->channel) {
> +            if (!rdma->is_return_path) {
> +                rdma_destroy_event_channel(rdma->channel);
> +            }
> +            rdma->channel = NULL;
> +        }
>      }
> +
>      if (rdma->channel) {
>          rdma_destroy_event_channel(rdma->channel);
>          rdma->channel = NULL;
> @@ -2561,6 +2577,25 @@ err_dest_init_create_listen_id:
>  
>  }
>  
> +static void qemu_rdma_return_path_dest_init(RDMAContext *rdma_return_path,
> +                                            RDMAContext *rdma)
> +{
> +    int idx;
> +
> +    for (idx = 0; idx < RDMA_WRID_MAX; idx++) {
> +        rdma_return_path->wr_data[idx].control_len = 0;
> +        rdma_return_path->wr_data[idx].control_curr = NULL;
> +    }
> +
> +    /*the CM channel and CM id is shared*/
> +    rdma_return_path->channel = rdma->channel;
> +    rdma_return_path->listen_id = rdma->listen_id;
> +
> +    rdma->return_path = rdma_return_path;
> +    rdma_return_path->return_path = rdma;
> +    rdma_return_path->is_return_path = true;
> +}
> +
>  static void *qemu_rdma_data_init(const char *host_port, Error **errp)
>  {
>      RDMAContext *rdma = NULL;
> @@ -3018,6 +3053,8 @@ err:
>      return ret;
>  }
>  
> +static void rdma_accept_incoming_migration(void *opaque);
> +
>  static int qemu_rdma_accept(RDMAContext *rdma)
>  {
>      RDMACapabilities cap;
> @@ -3112,7 +3149,14 @@ static int qemu_rdma_accept(RDMAContext *rdma)
>          }
>      }
>  
> -    qemu_set_fd_handler(rdma->channel->fd, NULL, NULL, NULL);
> +    /* Accept the second connection request for return path */
> +    if (migrate_postcopy() && !rdma->is_return_path) {
> +        qemu_set_fd_handler(rdma->channel->fd, rdma_accept_incoming_migration,
> +                            NULL,
> +                            (void *)(intptr_t)rdma->return_path);
> +    } else {
> +        qemu_set_fd_handler(rdma->channel->fd, NULL, NULL, NULL);
> +    }
>  
>      ret = rdma_accept(rdma->cm_id, &conn_param);
>      if (ret) {
> @@ -3693,6 +3737,10 @@ static void rdma_accept_incoming_migration(void *opaque)
>  
>      trace_qemu_rdma_accept_incoming_migration_accepted();
>  
> +    if (rdma->is_return_path) {
> +        return;
> +    }
> +
>      f = qemu_fopen_rdma(rdma, "rb");
>      if (f == NULL) {
>          ERROR(errp, "could not qemu_fopen_rdma!");
> @@ -3707,7 +3755,7 @@ static void rdma_accept_incoming_migration(void *opaque)
>  void rdma_start_incoming_migration(const char *host_port, Error **errp)
>  {
>      int ret;
> -    RDMAContext *rdma;
> +    RDMAContext *rdma, *rdma_return_path;
>      Error *local_err = NULL;
>  
>      trace_rdma_start_incoming_migration();
> @@ -3734,12 +3782,24 @@ void rdma_start_incoming_migration(const char *host_port, Error **errp)
>  
>      trace_rdma_start_incoming_migration_after_rdma_listen();
>  
> +    /* initialize the RDMAContext for return path */
> +    if (migrate_postcopy()) {
> +        rdma_return_path = qemu_rdma_data_init(host_port, &local_err);
> +
> +        if (rdma_return_path == NULL) {
> +            goto err;
> +        }
> +
> +        qemu_rdma_return_path_dest_init(rdma_return_path, rdma);
> +    }
> +
>      qemu_set_fd_handler(rdma->channel->fd, rdma_accept_incoming_migration,
>                          NULL, (void *)(intptr_t)rdma);
>      return;
>  err:
>      error_propagate(errp, local_err);
>      g_free(rdma);
> +    g_free(rdma_return_path);
>  }
>  
>  void rdma_start_outgoing_migration(void *opaque,
> @@ -3747,6 +3807,7 @@ void rdma_start_outgoing_migration(void *opaque,
>  {
>      MigrationState *s = opaque;
>      RDMAContext *rdma = qemu_rdma_data_init(host_port, errp);
> +    RDMAContext *rdma_return_path = NULL;
>      int ret = 0;
>  
>      if (rdma == NULL) {
> @@ -3767,6 +3828,32 @@ void rdma_start_outgoing_migration(void *opaque,
>          goto err;
>      }
>  
> +    /* RDMA postcopy need a seprate queue pair for return path */
> +    if (migrate_postcopy()) {
> +        rdma_return_path = qemu_rdma_data_init(host_port, errp);
> +
> +        if (rdma_return_path == NULL) {
> +            goto err;
> +        }
> +
> +        ret = qemu_rdma_source_init(rdma_return_path,
> +            s->enabled_capabilities[MIGRATION_CAPABILITY_RDMA_PIN_ALL], errp);
> +
> +        if (ret) {
> +            goto err;
> +        }
> +
> +        ret = qemu_rdma_connect(rdma_return_path, errp);
> +
> +        if (ret) {
> +            goto err;
> +        }
> +
> +        rdma->return_path = rdma_return_path;
> +        rdma_return_path->return_path = rdma;
> +        rdma_return_path->is_return_path = true;
> +    }
> +
>      trace_rdma_start_outgoing_migration_after_rdma_connect();
>  
>      s->to_dst_file = qemu_fopen_rdma(rdma, "wb");
> @@ -3774,4 +3861,5 @@ void rdma_start_outgoing_migration(void *opaque,
>      return;
>  err:
>      g_free(rdma);
> +    g_free(rdma_return_path);
>  }
> -- 
> 1.8.3.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK