On (Tue) 16 Jun 2015 [11:26:32], Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
>
> MIG_CMD_PACKAGED is a migration command that wraps a chunk of migration
> stream inside a package whose length can be determined purely by reading
> its header. The destination guarantees that the whole MIG_CMD_PACKAGED
> is read off the stream prior to parsing the contents.
>
> This is used by postcopy to load device state (from the package)
> while leaving the main stream free to receive memory pages.
Not sure why this is necessary. I suppose I'll have to go read the
documentation in patch 1..
However:
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -718,6 +718,50 @@ void qemu_savevm_send_open_return_path(QEMUFile *f)
> qemu_savevm_command_send(f, MIG_CMD_OPEN_RETURN_PATH, 0, NULL);
> }
>
> +/* We have a buffer of data to send; we don't want that all to be loaded
> + * by the command itself, so the command contains just the length of the
> + * extra buffer that we then send straight after it.
> + * TODO: Must be a better way to organise that
> + *
> + * Returns:
> + * 0 on success
> + * -ve on error
> + */
> +int qemu_savevm_send_packaged(QEMUFile *f, const QEMUSizedBuffer *qsb)
> +{
> + size_t cur_iov;
> + size_t len = qsb_get_length(qsb);
> + uint32_t tmp;
> +
> + if (len > MAX_VM_CMD_PACKAGED_SIZE) {
> + error_report("%s: Unreasonably large packaged state: %zu",
> + __func__, len);
> + return -1;
> + }
> +
> + tmp = cpu_to_be32(len);
> +
> + trace_qemu_savevm_send_packaged();
> + qemu_savevm_command_send(f, MIG_CMD_PACKAGED, 4, (uint8_t *)&tmp);
> +
> + /* all the data follows (concatinating the iov's) */
> + for (cur_iov = 0; cur_iov < qsb->n_iov; cur_iov++) {
> + /* The iov entries are partially filled */
> + size_t towrite = (qsb->iov[cur_iov].iov_len > len) ?
> + len :
> + qsb->iov[cur_iov].iov_len;
If iov_len was > len, we only wrote part of the current buffer, and we
skip to the next?
Amit
