Re: [PATCH v2 06/18] libxl: store a copy of configuration when creating domain

[Ian Campbell <ian.campbell@citrix.com>]

On Wed, 2014-07-30 at 19:23 +0100, Wei Liu wrote:
> The configuration is stored in libxl-json format. It will be used as
> template to reconstruct domain configuration during runtime.
> 
> There's only one write to disk when domain creation finishes. We
> therefore has a window that the domain exists but has no JSON config in

"therefore have a window".

> disk. We define this state as domain being created or destroyed. Any
> other operations that need to access JSON config should bail.
> 
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>

Acked-by: Ian Campbell <ian.campbell@citrix.com>

> ---
>  tools/libxl/libxl_create.c   |   22 ++++++++++++++++++++++
>  tools/libxl/libxl_internal.c |   21 +++++++++++++++++++++
>  tools/libxl/libxl_internal.h |   21 +++++++++++++++++++++
>  3 files changed, 64 insertions(+)
> 
> diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
> index 0686f96..c997d7a 100644
> --- a/tools/libxl/libxl_create.c
> +++ b/tools/libxl/libxl_create.c
> @@ -1350,10 +1350,30 @@ static void domcreate_complete(libxl__egc *egc,
>  {
>      STATE_AO_GC(dcs->ao);
>      libxl_domain_config *const d_config = dcs->guest_config;
> +    libxl_domain_config *d_config_saved = &dcs->guest_config_saved;
>  
>      if (!rc && d_config->b_info.exec_ssidref)
>          rc = xc_flask_relabel_domain(CTX->xch, dcs->guest_domid, d_config->b_info.exec_ssidref);
>  
> +    if (!rc) {
> +        libxl__carefd *lock;
> +
> +        /* Note that we hold CTX lock at this point so only need to
> +         * take data store lock
> +         */
> +        lock = libxl__lock_domain_data(gc, dcs->guest_domid);
> +        if (!lock) {
> +            rc = ERROR_LOCK_FAIL;
> +        } else {
> +            libxl__update_domain_configuration(gc, d_config_saved, d_config);
> +            rc = libxl__set_domain_configuration(gc, dcs->guest_domid,
> +                                                 d_config_saved);
> +            libxl__unlock_domain_data(lock);
> +        }
> +    }
> +
> +    libxl_domain_config_dispose(d_config_saved);
> +
>      if (rc) {
>          if (dcs->guest_domid) {
>              dcs->dds.ao = ao;
> @@ -1404,6 +1424,8 @@ static int do_domain_create(libxl_ctx *ctx, libxl_domain_config *d_config,
>      GCNEW(cdcs);
>      cdcs->dcs.ao = ao;
>      cdcs->dcs.guest_config = d_config;
> +    libxl_domain_config_init(&cdcs->dcs.guest_config_saved);
> +    libxl_domain_config_copy(ctx, &cdcs->dcs.guest_config_saved, d_config);
>      cdcs->dcs.restore_fd = restore_fd;
>      cdcs->dcs.callback = domain_create_cb;
>      cdcs->dcs.checkpointed_stream = checkpointed_stream;
> diff --git a/tools/libxl/libxl_internal.c b/tools/libxl/libxl_internal.c
> index 052315b..a002899 100644
> --- a/tools/libxl/libxl_internal.c
> +++ b/tools/libxl/libxl_internal.c
> @@ -506,6 +506,27 @@ out:
>      return rc;
>  }
>  
> +void libxl__update_domain_configuration(libxl__gc *gc,
> +                                        libxl_domain_config *dst,
> +                                        const libxl_domain_config *src)
> +{
> +    int i;
> +
> +    /* update network interface information */
> +    for (i = 0; i < src->num_nics; i++)
> +        libxl__update_config_nic(gc, &dst->nics[i], &src->nics[i]);
> +
> +    /* update vtpm information */
> +    for (i = 0; i < src->num_vtpms; i++)
> +        libxl__update_config_vtpm(gc, &dst->vtpms[i], &src->vtpms[i]);
> +
> +    /* update guest UUID */
> +    libxl_uuid_copy(CTX, &dst->c_info.uuid, &src->c_info.uuid);
> +
> +    /* video ram */
> +    dst->b_info.video_memkb = src->b_info.video_memkb;
> +}
> +
>  /*
>   * Local variables:
>   * mode: C
> diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
> index 52d4d6c..02708c7 100644
> --- a/tools/libxl/libxl_internal.h
> +++ b/tools/libxl/libxl_internal.h
> @@ -2779,6 +2779,7 @@ struct libxl__domain_create_state {
>      /* filled in by user */
>      libxl__ao *ao;
>      libxl_domain_config *guest_config;
> +    libxl_domain_config guest_config_saved; /* vanilla config */
>      int restore_fd;
>      libxl__domain_create_cb *callback;
>      libxl_asyncprogress_how aop_console_how;
> @@ -3247,6 +3248,26 @@ int libxl__get_domain_configuration(libxl__gc *gc, uint32_t domid,
>  int libxl__set_domain_configuration(libxl__gc *gc, uint32_t domid,
>                                      libxl_domain_config *d_config);
>  
> +/* ------ Things related to updating domain configurations ----- */
> +void libxl__update_domain_configuration(libxl__gc *gc,
> +                                        libxl_domain_config *dst,
> +                                        const libxl_domain_config *src);
> +static inline void libxl__update_config_nic(libxl__gc *gc,
> +                                            libxl_device_nic *dst,
> +                                            libxl_device_nic *src)
> +{
> +    dst->devid = src->devid;
> +    libxl_mac_copy(CTX, &dst->mac, &src->mac);
> +}
> +
> +static inline void libxl__update_config_vtpm(libxl__gc *gc,
> +                                             libxl_device_vtpm *dst,
> +                                             libxl_device_vtpm *src)
> +{
> +    dst->devid = src->devid;
> +    libxl_uuid_copy(CTX, &dst->uuid, &src->uuid);
> +}
> +
>  #endif
>  
>  /*