Re: [Qemu-devel] [RFC PATCH v2 15/16] Wire in BER visitors

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Apr 23, 2014 at 05:37:48PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> BER output visitor to be selected with env
> BER input visitor recognized by file header
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
>  include/migration/migration.h |   2 +
>  savevm.c                      | 105 +++++++++++++++++++++++++++++++-----------
>  2 files changed, 80 insertions(+), 27 deletions(-)
> 
> diff --git a/include/migration/migration.h b/include/migration/migration.h
> index 8111125..5d500ec 100644
> --- a/include/migration/migration.h
> +++ b/include/migration/migration.h
> @@ -27,6 +27,8 @@
>  #define QEMU_VM_FILE_VERSION_COMPAT  0x00000002
>  #define QEMU_VM_FILE_VERSION         0x00000003
>  
> +#define QEMU_VM_BER_FILE_MAGIC       0x7fcdc551
> +

Where does this come from? I presume this matches
something in BER format?

>  #define QEMU_VM_EOF                  0x00
>  #define QEMU_VM_SECTION_START        0x01
>  #define QEMU_VM_SECTION_PART         0x02
> diff --git a/savevm.c b/savevm.c
> index 515dd77..2bbbcdc 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -24,6 +24,8 @@
>  
>  #include "config-host.h"
>  #include "qemu-common.h"
> +#include "qapi/qemu-file-ber-output-visitor.h"
> +#include "qapi/qemu-file-ber-input-visitor.h"
>  #include "qapi/qemu-file-binary-input-visitor.h"
>  #include "qapi/qemu-file-binary-output-visitor.h"
>  #include "hw/hw.h"
> @@ -527,6 +529,34 @@ bool qemu_savevm_state_blocked(Error **errp)
>      return false;
>  }
>  
> +/* Return a visitor for use on the QEMUFile; visit_destroy should be
> + * called on it to clean it up.
> + */
> +static Visitor *qemu_savevm_get_visitor(QEMUFile *f)
> +{
> +    char *formatvar = getenv("QEMUMIGFORMAT");
> +
> +    if (formatvar && (!strcmp(formatvar, "BER"))) {
> +        QemuFileBEROutputVisitor *qfberov = qemu_file_ber_output_visitor_new(f);
> +        Visitor *v = qemu_file_ber_output_get_visitor(qfberov);
> +
> +        qemu_file_set_tmp_visitor(f, v);
> +        return v;
> +    }
> +
> +    if (formatvar) {
> +        error_report("QEMUMIGFORMAT set to unknown value '%s'", formatvar);
> +        assert(0);
> +    }
> +
> +    QemuFileBinOutputVisitor *qfbov = qemu_file_bin_output_visitor_new(f);
> +    Visitor *v = qemu_file_bin_output_get_visitor(qfbov);
> +
> +    qemu_file_set_tmp_visitor(f, v);
> +
> +    return v;
> +}
> +
>  void qemu_savevm_state_begin(QEMUFile *f,
>                               const MigrationParams *params)
>  {
> @@ -534,10 +564,7 @@ void qemu_savevm_state_begin(QEMUFile *f,
>      int ret;
>      Error *local_err = NULL;
>      SectionHeader sh;
> -
> -    QemuFileBinOutputVisitor *qfbov = qemu_file_bin_output_visitor_new(f);
> -    Visitor *v = qemu_file_bin_output_get_visitor(qfbov);
> -    qemu_file_set_tmp_visitor(f, v);
> +    Visitor *v = qemu_savevm_get_visitor(f);
>  
>      trace_savevm_state_begin();
>      QTAILQ_FOREACH(se, &savevm_handlers, entry) {
> @@ -789,13 +816,11 @@ static int qemu_savevm_state(QEMUFile *f)
>  
>  static int qemu_save_device_state(QEMUFile *f)
>  {
> +    Visitor *v = qemu_savevm_get_visitor(f);
>      SaveStateEntry *se;
>      Error *local_err;
>      SectionHeader sh;
>  
> -    QemuFileBinOutputVisitor *qfbov = qemu_file_bin_output_visitor_new(f);
> -    qemu_file_set_tmp_visitor(f, qemu_file_bin_output_get_visitor(qfbov));
> -    Visitor *v = qemu_file_bin_output_get_visitor(qfbov);
>      int32_t section_type;
>  
>      cpu_synchronize_all_states();
> @@ -861,41 +886,65 @@ typedef struct LoadStateEntry {
>      int version_id;
>  } LoadStateEntry;
>  
> +/* Given a just opened input QEMUFile, peak at the header and figure
> + * out which visitor should be used for it.
> + * Return the visitor ready for use.
> + */
> +static Visitor *pick_input_visitor(QEMUFile *f)
> +{
> +    uint32_t tmp32;
> +
> +    if (qemu_peek_buffer(f, (uint8_t *)&tmp32, 4, 0) != 4) {
> +        fprintf(stderr, "Failed to read SaveVM header word\n");
> +        return NULL;
> +    }
> +
> +    tmp32 = be32_to_cpu(tmp32);
> +
> +    switch (tmp32) {
> +    case QEMU_VM_FILE_MAGIC: {
> +        QemuFileBinInputVisitor *qfbiv = qemu_file_bin_input_visitor_new(f);
> +        Visitor *v = qemu_file_bin_input_get_visitor(qfbiv);
> +        qemu_file_set_tmp_visitor(f, v);
> +
> +        return v;
> +        }
> +
> +    case QEMU_VM_BER_FILE_MAGIC: {
> +        QemuFileBERInputVisitor *qfberiv = qemu_file_ber_input_visitor_new(f);
> +        Visitor *v = qemu_file_ber_input_get_visitor(qfberiv);
> +        qemu_file_set_tmp_visitor(f, v);
> +
> +        return v;
> +        }
> +
> +    default:
> +        fprintf(stderr, "Invalid SaveVM header (0x%x)\n", tmp32);
> +        return NULL;
> +    }
> +}
> +
>  int qemu_loadvm_state(QEMUFile *f)
>  {
>      QLIST_HEAD(, LoadStateEntry) loadvm_handlers =
>          QLIST_HEAD_INITIALIZER(loadvm_handlers);
>      LoadStateEntry *le, *new_le;
> +    Visitor *v;
>      Error *local_err = NULL;
>      int32_t section_type;
> -    unsigned int tmp;
>      int ret;
>  
>      if (qemu_savevm_state_blocked(NULL)) {
>          return -EINVAL;
>      }
>  
> -    tmp = qemu_get_be32(f);
> -    if (tmp != QEMU_VM_FILE_MAGIC) {
> -        return -EINVAL;
> -    }
> -
> -    tmp = qemu_get_be32(f);
> -    if (tmp == QEMU_VM_FILE_VERSION_COMPAT) {
> -        error_report("SaveVM v2 format is obsolete and don't work anymore");
> +    v = pick_input_visitor(f);
> +    if (!v) {
>          return -ENOTSUP;
>      }
> -    if (tmp != QEMU_VM_FILE_VERSION) {
> -        return -ENOTSUP;
> -    }
> -
> -    /* TODO: Here we should be able to figure out if it's a binary file
> -     * or what and open the right type of visitor
> -     */
> -    QemuFileBinInputVisitor *qfbiv = qemu_file_bin_input_visitor_new(f);
> -    Visitor *v = qemu_file_bin_input_get_visitor(qfbiv);
> -    qemu_file_set_tmp_visitor(f, v);
>  
> +    visit_start_sequence_compat(v, "file", VISIT_SEQ_COMPAT_FILE, NULL,
> +                                &local_err);
>      visit_start_sequence_compat(v, "top", VISIT_SEQ_COMPAT_BYTE0TERM,
>                                  NULL, &local_err);
>      while (visit_get_next_type(v, &section_type, NULL, "section", &local_err),
> @@ -912,6 +961,7 @@ int qemu_loadvm_state(QEMUFile *f)
>                        "secstart" : "secfull",
>                    VISIT_SEQ_COMPAT_SECTION_HEADER, &sh, &local_err);
>              if (local_err) {
> +                error_report("%s", error_get_pretty(local_err));
>                  ret = -EINVAL;
>                  goto out;
>              }
> @@ -1001,6 +1051,7 @@ out:
>      }
>  
>      visit_end_sequence_compat(v, "top", VISIT_SEQ_COMPAT_BYTE0TERM, &local_err);
> +    visit_end_sequence_compat(v, "file", VISIT_SEQ_COMPAT_FILE, &local_err);
>      if (local_err) {
>          error_report("%s", error_get_pretty(local_err));
>          ret = -EINVAL;
> @@ -1010,7 +1061,7 @@ out:
>          ret = qemu_file_get_error(f);
>      }
>  
> -    qemu_file_bin_input_visitor_cleanup(qfbiv);
> +    visit_destroy(v, &local_err);
>      return ret;
>  }
>  
> -- 
> 1.9.0