Re: [PATCH v2 07/17] migration: Add qemu_loadvm_load_state_buffer() and its handler

[Avihai Horon <avihaih@nvidia.com>]

On 27/08/2024 20:54, Maciej S. Szmigiero wrote:
> External email: Use caution opening links or attachments
>
>
> From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>
>
> qemu_loadvm_load_state_buffer() and its load_state_buffer
> SaveVMHandler allow providing device state buffer to explicitly
> specified device via its idstr and instance id.
>
> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
> ---
>   include/migration/register.h | 15 +++++++++++++++
>   migration/savevm.c           | 25 +++++++++++++++++++++++++
>   migration/savevm.h           |  3 +++
>   3 files changed, 43 insertions(+)
>
> diff --git a/include/migration/register.h b/include/migration/register.h
> index 9de123252edf..4a578f140713 100644
> --- a/include/migration/register.h
> +++ b/include/migration/register.h
> @@ -263,6 +263,21 @@ typedef struct SaveVMHandlers {
>        */
>       int (*load_state)(QEMUFile *f, void *opaque, int version_id);
>
> +    /**
> +     * @load_state_buffer
> +     *
> +     * Load device state buffer provided to qemu_loadvm_load_state_buffer().
> +     *
> +     * @opaque: data pointer passed to register_savevm_live()
> +     * @data: the data buffer to load
> +     * @data_size: the data length in buffer
> +     * @errp: pointer to Error*, to store an error if it happens.
> +     *
> +     * Returns zero to indicate success and negative for error
> +     */
> +    int (*load_state_buffer)(void *opaque, char *data, size_t data_size,
> +                             Error **errp);

Nit: Maybe rename data to buf and data_size to len to be consistent with 
qemu_loadvm_load_state_buffer()?

> +
>       /**
>        * @load_setup
>        *
> diff --git a/migration/savevm.c b/migration/savevm.c
> index d43acbbf20cf..3fde5ca8c26b 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -3101,6 +3101,31 @@ int qemu_loadvm_approve_switchover(void)
>       return migrate_send_rp_switchover_ack(mis);
>   }
>
> +int qemu_loadvm_load_state_buffer(const char *idstr, uint32_t instance_id,
> +                                  char *buf, size_t len, Error **errp)
> +{
> +    SaveStateEntry *se;
> +
> +    se = find_se(idstr, instance_id);
> +    if (!se) {
> +        error_setg(errp, "Unknown idstr %s or instance id %u for load state buffer",
> +                   idstr, instance_id);
> +        return -1;
> +    }
> +
> +    if (!se->ops || !se->ops->load_state_buffer) {
> +        error_setg(errp, "idstr %s / instance %u has no load state buffer operation",
> +                   idstr, instance_id);
> +        return -1;
> +    }
> +
> +    if (se->ops->load_state_buffer(se->opaque, buf, len, errp) != 0) {
> +        return -1;
> +    }
> +
> +    return 0;

Nit: this can be simplified to:
return se->ops->load_state_buffer(se->opaque, buf, len, errp);

Thanks.

> +}
> +
>   bool save_snapshot(const char *name, bool overwrite, const char *vmstate,
>                     bool has_devices, strList *devices, Error **errp)
>   {
> diff --git a/migration/savevm.h b/migration/savevm.h
> index 9ec96a995c93..d388f1bfca98 100644
> --- a/migration/savevm.h
> +++ b/migration/savevm.h
> @@ -70,4 +70,7 @@ int qemu_loadvm_approve_switchover(void);
>   int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
>           bool in_postcopy, bool inactivate_disks);
>
> +int qemu_loadvm_load_state_buffer(const char *idstr, uint32_t instance_id,
> +                                  char *buf, size_t len, Error **errp);
> +
>   #endif