Re: [Qemu-devel] [PATCH COLO-Frame v18 12/34] COLO: Load VMState into buffer before restore it

[Dr. David Alan Gilbert]

* zhanghailiang (address@hidden) wrote:
> We should not destroy the state of SVM (Secondary VM) until we receive
> the whole state from the PVM (Primary VM), in case the primary fails in
> the middle of sending the state, so, here we cache the device state in
> Secondary before restore it.
> 
> Besides, we should call qemu_system_reset() before load VM state,
> which can ensure the data is intact.
> 
> Signed-off-by: zhanghailiang <address@hidden>
> Signed-off-by: Li Zhijian <address@hidden>
> Signed-off-by: Gonglei <address@hidden>
> Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> Cc: Dr. David Alan Gilbert <address@hidden>
> ---
> v17:
> - Replace the old buffer API with the new channel buffer API.
> v16:
> - Rename colo_get_cmd_value() to colo_receive_mesage_value();
> v13:
> - Fix the define of colo_get_cmd_value() to use 'Error **errp' instead of
>   return value.
> v12:
> - Use the new helper colo_get_cmd_value() instead of colo_ctl_get()
> ---
>  migration/colo.c | 70 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 68 insertions(+), 2 deletions(-)
> 
> diff --git a/migration/colo.c b/migration/colo.c
> index 0401629..8fa2104 100644
> --- a/migration/colo.c
> +++ b/migration/colo.c
> @@ -115,6 +115,28 @@ static void colo_receive_check_message(QEMUFile *f, 
> COLOMessage expect_msg,
>      }
>  }
>  
> +static uint64_t colo_receive_message_value(QEMUFile *f, uint32_t expect_msg,
> +                                           Error **errp)
> +{
> +    Error *local_err = NULL;
> +    uint64_t value;
> +    int ret;
> +
> +    colo_receive_check_message(f, expect_msg, &local_err);
> +    if (local_err) {
> +        error_propagate(errp, local_err);
> +        return 0;
> +    }
> +
> +    value = qemu_get_be64(f);
> +    ret = qemu_file_get_error(f);
> +    if (ret < 0) {
> +        error_setg_errno(errp, -ret, "Failed to get value for COLO message: 
> %s",
> +                         COLOMessage_lookup[expect_msg]);
> +    }
> +    return value;
> +}
> +
>  static int colo_do_checkpoint_transaction(MigrationState *s,
>                                            QIOChannelBuffer *bioc,
>                                            QEMUFile *fb)
> @@ -286,6 +308,10 @@ static void colo_wait_handle_message(QEMUFile *f, int 
> *checkpoint_request,
>  void *colo_process_incoming_thread(void *opaque)
>  {
>      MigrationIncomingState *mis = opaque;
> +    QEMUFile *fb = NULL;
> +    QIOChannelBuffer *bioc = NULL; /* Cache incoming device state */
> +    uint64_t total_size;
> +    uint64_t value;
>      Error *local_err = NULL;
>      int ret;
>  
> @@ -310,6 +336,10 @@ void *colo_process_incoming_thread(void *opaque)
>          goto out;
>      }
>  
> +    bioc = qio_channel_buffer_new(COLO_BUFFER_BASE_SIZE);
> +    fb = qemu_fopen_channel_input(QIO_CHANNEL(bioc));
> +    object_unref(OBJECT(bioc));
> +
>      colo_send_message(mis->to_src_file, COLO_MESSAGE_CHECKPOINT_READY,
>                        &local_err);
>      if (local_err) {
> @@ -337,7 +367,30 @@ void *colo_process_incoming_thread(void *opaque)
>              goto out;
>          }
>  
> -        /* TODO: read migration data into colo buffer */
> +        value = colo_receive_message_value(mis->from_src_file,
> +                                 COLO_MESSAGE_VMSTATE_SIZE, &local_err);
> +        if (local_err) {
> +            goto out;
> +        }
> +
> +        /*
> +         * Read VM device state data into channel buffer,
> +         * It's better to re-use the memory allocated.
> +         * Here we need to handle the channel buffer directly.
> +         */
> +        if (value > bioc->capacity) {
> +            bioc->capacity = value;
> +            bioc->data = g_realloc(bioc->data, bioc->capacity);
> +        }

Dan: Are you ok with that, or should there be some io/channel-buffer.c call
to do it?

Dave

> +        total_size = qemu_get_buffer(mis->from_src_file, bioc->data, value);
> +        if (total_size != value) {
> +            error_report("Got %lu VMState data, less than expected %lu",
> +                         total_size, value);
> +            ret = -EINVAL;
> +            goto out;
> +        }
> +        bioc->usage = total_size;
> +        qio_channel_io_seek(QIO_CHANNEL(bioc), 0, 0, NULL);
>  
>          colo_send_message(mis->to_src_file, COLO_MESSAGE_VMSTATE_RECEIVED,
>                       &local_err);
> @@ -345,7 +398,16 @@ void *colo_process_incoming_thread(void *opaque)
>              goto out;
>          }
>  
> -        /* TODO: load vm state */
> +        qemu_mutex_lock_iothread();
> +        qemu_system_reset(VMRESET_SILENT);
> +        if (qemu_loadvm_state(fb) < 0) {
> +            error_report("COLO: loadvm failed");
> +            qemu_mutex_unlock_iothread();
> +            goto out;
> +        }
> +        qemu_mutex_unlock_iothread();
> +
> +        /* TODO: flush vm state */
>  
>          colo_send_message(mis->to_src_file, COLO_MESSAGE_VMSTATE_LOADED,
>                       &local_err);
> @@ -360,6 +422,10 @@ out:
>          error_report_err(local_err);
>      }
>  
> +    if (fb) {
> +        qemu_fclose(fb);
> +    }
> +
>      qemu_mutex_lock_iothread();
>      colo_release_ram_cache();
>      qemu_mutex_unlock_iothread();
> -- 
> 1.8.3.1
> 
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK