[Qemu-devel] Re: [RFC PATCH 10/20] Introduce skip_header parameter to qemu_loadvm_state() so that it can be called iteratively without reading the header.

[Anthony Liguori <aliguori@linux.vnet.ibm.com>]

On 04/21/2010 12:57 AM, Yoshiaki Tamura wrote:
> Signed-off-by: Yoshiaki Tamura<tamura.yoshiaki@lab.ntt.co.jp>
>    

I think the more appropriate thing to do is have 
qemu_savevm_state_complete() not write QEMU_VM_EOF when doing a 
continuous live migration.

You would then want qemu_loadvm_state() to detect real EOF and treat 
that the same as QEMU_VM_EOF (provided it occurred at a section boundary).

Of course, this should be a flag to qemu_loadvm_state() as it's not 
always the right behavior.

Regards,

Anthony Liguori

> ---
>   migration-exec.c |    2 +-
>   migration-fd.c   |    2 +-
>   migration-tcp.c  |    2 +-
>   migration-unix.c |    2 +-
>   savevm.c         |   25 ++++++++++++++-----------
>   sysemu.h         |    2 +-
>   6 files changed, 19 insertions(+), 16 deletions(-)
>
> diff --git a/migration-exec.c b/migration-exec.c
> index 3edc026..5839a6d 100644
> --- a/migration-exec.c
> +++ b/migration-exec.c
> @@ -113,7 +113,7 @@ static void exec_accept_incoming_migration(void *opaque)
>       QEMUFile *f = opaque;
>       int ret;
>
> -    ret = qemu_loadvm_state(f);
> +    ret = qemu_loadvm_state(f, 0);
>       if (ret<  0) {
>           fprintf(stderr, "load of migration failed\n");
>           goto err;
> diff --git a/migration-fd.c b/migration-fd.c
> index 0cc74ad..0e97ed0 100644
> --- a/migration-fd.c
> +++ b/migration-fd.c
> @@ -106,7 +106,7 @@ static void fd_accept_incoming_migration(void *opaque)
>       QEMUFile *f = opaque;
>       int ret;
>
> -    ret = qemu_loadvm_state(f);
> +    ret = qemu_loadvm_state(f, 0);
>       if (ret<  0) {
>           fprintf(stderr, "load of migration failed\n");
>           goto err;
> diff --git a/migration-tcp.c b/migration-tcp.c
> index 56e1a3b..94a1a03 100644
> --- a/migration-tcp.c
> +++ b/migration-tcp.c
> @@ -182,7 +182,7 @@ static void tcp_accept_incoming_migration(void *opaque)
>           goto out;
>       }
>
> -    ret = qemu_loadvm_state(f);
> +    ret = qemu_loadvm_state(f, 0);
>       if (ret<  0) {
>           fprintf(stderr, "load of migration failed\n");
>           goto out_fopen;
> diff --git a/migration-unix.c b/migration-unix.c
> index b7aab38..dd99a73 100644
> --- a/migration-unix.c
> +++ b/migration-unix.c
> @@ -168,7 +168,7 @@ static void unix_accept_incoming_migration(void *opaque)
>           goto out;
>       }
>
> -    ret = qemu_loadvm_state(f);
> +    ret = qemu_loadvm_state(f, 0);
>       if (ret<  0) {
>           fprintf(stderr, "load of migration failed\n");
>           goto out_fopen;
> diff --git a/savevm.c b/savevm.c
> index 22d928c..a401b27 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -1554,7 +1554,7 @@ typedef struct LoadStateEntry {
>       int version_id;
>   } LoadStateEntry;
>
> -int qemu_loadvm_state(QEMUFile *f)
> +int qemu_loadvm_state(QEMUFile *f, int skip_header)
>   {
>       QLIST_HEAD(, LoadStateEntry) loadvm_handlers =
>           QLIST_HEAD_INITIALIZER(loadvm_handlers);
> @@ -1563,17 +1563,20 @@ int qemu_loadvm_state(QEMUFile *f)
>       unsigned int v;
>       int ret;
>
> -    v = qemu_get_be32(f);
> -    if (v != QEMU_VM_FILE_MAGIC)
> -        return -EINVAL;
> +    if (!skip_header) {
> +        v = qemu_get_be32(f);
> +        if (v != QEMU_VM_FILE_MAGIC)
> +            return -EINVAL;
> +
> +        v = qemu_get_be32(f);
> +        if (v == QEMU_VM_FILE_VERSION_COMPAT) {
> +            fprintf(stderr, "SaveVM v3 format is obsolete and don't work anymore\n");
> +            return -ENOTSUP;
> +        }
> +        if (v != QEMU_VM_FILE_VERSION)
> +            return -ENOTSUP;
>
> -    v = qemu_get_be32(f);
> -    if (v == QEMU_VM_FILE_VERSION_COMPAT) {
> -        fprintf(stderr, "SaveVM v2 format is obsolete and don't work anymore\n");
> -        return -ENOTSUP;
>       }
> -    if (v != QEMU_VM_FILE_VERSION)
> -        return -ENOTSUP;
>
>       while ((section_type = qemu_get_byte(f)) != QEMU_VM_EOF) {
>           uint32_t instance_id, version_id, section_id;
> @@ -1898,7 +1901,7 @@ int load_vmstate(Monitor *mon, const char *name)
>           monitor_printf(mon, "Could not open VM state file\n");
>           return -EINVAL;
>       }
> -    ret = qemu_loadvm_state(f);
> +    ret = qemu_loadvm_state(f, 0);
>       qemu_fclose(f);
>       if (ret<  0) {
>           monitor_printf(mon, "Error %d while loading VM state\n", ret);
> diff --git a/sysemu.h b/sysemu.h
> index 647a468..6c1441f 100644
> --- a/sysemu.h
> +++ b/sysemu.h
> @@ -68,7 +68,7 @@ int qemu_savevm_state_begin(Monitor *mon, QEMUFile *f, int blk_enable,
>   int qemu_savevm_state_iterate(Monitor *mon, QEMUFile *f);
>   int qemu_savevm_state_complete(Monitor *mon, QEMUFile *f);
>   void qemu_savevm_state_cancel(Monitor *mon, QEMUFile *f);
> -int qemu_loadvm_state(QEMUFile *f);
> +int qemu_loadvm_state(QEMUFile *f, int skip_header);
>
>   void qemu_errors_to_file(FILE *fp);
>   void qemu_errors_to_mon(Monitor *mon);
>