Re: [PATCH v10 11/11] (lib)xl: soft reset support

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Tue, Jul 28, 2015 at 03:28:16PM +0200, Vitaly Kuznetsov wrote:
> Use existing create/restore path to perform 'soft reset' for HVM
> domains. Tear everything down, e.g. destroy domain's device model,
> remove the domain from xenstore, save toolstack record and start
> over.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>


> ---
> Changes since v9:
> - s,reset,Reset, in xl.cfg.pod.5 [Konrad Rzeszutek Wilk]
> - full stops in comments/log messages [Konrad Rzeszutek Wilk]
> - reword the need to remove the domain from xs [Konrad Rzeszutek Wilk]
> - rebase on top of current staging, minor fixes to adapt to Andrew's
>   changes.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  docs/man/xl.cfg.pod.5        |   7 +-
>  tools/libxl/libxl.c          |  23 ++++-
>  tools/libxl/libxl.h          |  15 ++++
>  tools/libxl/libxl_create.c   | 195 ++++++++++++++++++++++++++++++++++++++-----
>  tools/libxl/libxl_internal.h |   4 +
>  tools/libxl/libxl_types.idl  |   2 +
>  tools/libxl/xl.h             |   1 +
>  tools/libxl/xl_cmdimpl.c     |  25 +++++-
>  8 files changed, 243 insertions(+), 29 deletions(-)
> 
> diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
> index 69935d9..561710a 100644
> --- a/docs/man/xl.cfg.pod.5
> +++ b/docs/man/xl.cfg.pod.5
> @@ -346,6 +346,11 @@ destroy the domain.
>  write a "coredump" of the domain to F</var/lib/xen/dump/NAME> and then
>  restart the domain.
>  
> +=item B<soft-reset>
> +
> +Reset all Xen specific interfaces for the Xen-aware HVM domain allowing
> +it to reastablish these interfaces and continue executing the domain.
> +
>  =back
>  
>  The default for C<on_poweroff> is C<destroy>.
> @@ -367,7 +372,7 @@ Action to take if the domain crashes.  Default is C<destroy>.
>  =item B<on_soft_reset="ACTION">
>  
>  Action to take if the domain performs 'soft reset' (e.g. does kexec).
> -Default is C<restart>.
> +Default is C<soft-reset>.
>  
>  =back
>  
> diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
> index ff0d616..5f5559b 100644
> --- a/tools/libxl/libxl.c
> +++ b/tools/libxl/libxl.c
> @@ -1478,6 +1478,7 @@ void libxl__domain_destroy(libxl__egc *egc, libxl__domain_destroy_state *dds)
>          dds->stubdom.ao = ao;
>          dds->stubdom.domid = stubdomid;
>          dds->stubdom.callback = stubdom_destroy_callback;
> +        dds->stubdom.soft_reset = false;
>          libxl__destroy_domid(egc, &dds->stubdom);
>      } else {
>          dds->stubdom_finished = 1;
> @@ -1486,6 +1487,7 @@ void libxl__domain_destroy(libxl__egc *egc, libxl__domain_destroy_state *dds)
>      dds->domain.ao = ao;
>      dds->domain.domid = dds->domid;
>      dds->domain.callback = domain_destroy_callback;
> +    dds->domain.soft_reset = dds->soft_reset;
>      libxl__destroy_domid(egc, &dds->domain);
>  }
>  
> @@ -1666,10 +1668,14 @@ static void devices_destroy_cb(libxl__egc *egc,
>  
>      /* Clean up qemu-save and qemu-resume files. They are
>       * intermediate files created by libxc. Unfortunately they
> -     * don't fit in existing userdata scheme very well.
> +     * don't fit in existing userdata scheme very well. In soft reset
> +     * case we need to keep the file.
>       */
> -    rc = libxl__remove_file(gc, libxl__device_model_savefile(gc, domid));
> -    if (rc < 0) goto out;
> +    if (!dis->soft_reset) {
> +        rc = libxl__remove_file(gc,
> +                                libxl__device_model_savefile(gc, domid));
> +        if (rc < 0) goto out;
> +    }
>      rc = libxl__remove_file(gc,
>               GCSPRINTF(XC_DEVICE_MODEL_RESTORE_FILE".%u", domid));
>      if (rc < 0) goto out;
> @@ -1680,7 +1686,16 @@ static void devices_destroy_cb(libxl__egc *egc,
>          ctx->xch = xc_interface_open(ctx->lg,0,0);
>          if (!ctx->xch) goto badchild;
>  
> -        rc = xc_domain_destroy(ctx->xch, domid);
> +        if (!dis->soft_reset) {
> +            rc = xc_domain_destroy(ctx->xch, domid);
> +        }
> +        else {
> +            rc = xc_domain_pause(ctx->xch, domid);
> +            if (rc < 0) goto badchild;
> +            rc = xc_domain_soft_reset(ctx->xch, domid);
> +            if (rc < 0) goto badchild;
> +            rc = xc_domain_unpause(ctx->xch, domid);
> +        }
>          if (rc < 0) goto badchild;
>          _exit(0);
>  
> diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
> index 5f9047c..4ee9fbf 100644
> --- a/tools/libxl/libxl.h
> +++ b/tools/libxl/libxl.h
> @@ -205,6 +205,13 @@
>  #define LIBXL_HAVE_BUILDINFO_ARM_GIC_VERSION 1
>  
>  /*
> + * LIBXL_HAVE_SOFT_RESET indicates that libxl supports performing
> + * 'soft reset' for domains and there is 'soft_reset' shutdown reason
> + * in enum libxl_shutdown_reason.
> + */
> +#define LIBXL_HAVE_SOFT_RESET 1
> +
> +/*
>   * libxl ABI compatibility
>   *
>   * The only guarantee which libxl makes regarding ABI compatibility
> @@ -1132,6 +1139,14 @@ int static inline libxl_domain_create_restore_0x040200(
>  
>  #endif
>  
> +int libxl_domain_soft_reset(libxl_ctx *ctx,
> +                            libxl_domain_config *d_config,
> +                            uint32_t domid,
> +                            const libxl_asyncop_how *ao_how,
> +                            const libxl_asyncprogress_how
> +                            *aop_console_how)
> +                            LIBXL_EXTERNAL_CALLERS_ONLY;
> +
>    /* A progress report will be made via ao_console_how, of type
>     * domain_create_console_available, when the domain's primary
>     * console is available and can be connected to.
> diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
> index 855b42c..dc9b9d6 100644
> --- a/tools/libxl/libxl_create.c
> +++ b/tools/libxl/libxl_create.c
> @@ -496,8 +496,6 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
>      /* convenience aliases */
>      libxl_domain_create_info *info = &d_config->c_info;
>  
> -    assert(!libxl_domid_valid_guest(*domid));
> -
>      uuid_string = libxl__uuid2string(gc, info->uuid);
>      if (!uuid_string) {
>          rc = ERROR_NOMEM;
> @@ -518,7 +516,6 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
>          }
>          flags |= XEN_DOMCTL_CDF_hap;
>      }
> -    *domid = -1;
>  
>      /* Ultimately, handle is an array of 16 uint8_t, same as uuid */
>      libxl_uuid_copy(ctx, (libxl_uuid *)handle, &info->uuid);
> @@ -530,13 +527,17 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
>          goto out;
>      }
>  
> -    ret = xc_domain_create_config(ctx->xch, info->ssidref,
> -                                  handle, flags, domid,
> -                                  xc_config);
> -    if (ret < 0) {
> -        LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "domain creation fail");
> -        rc = ERROR_FAIL;
> -        goto out;
> +    /* Valid domid here means we're soft resetting. */
> +    if (!libxl_domid_valid_guest(*domid)) {
> +        ret = xc_domain_create_config(ctx->xch, info->ssidref,
> +                                      handle, flags, domid,
> +                                      xc_config);
> +        if (ret < 0) {
> +            LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR,
> +                             "domain creation fail");
> +            rc = ERROR_FAIL;
> +            goto out;
> +        }
>      }
>  
>      rc = libxl__arch_domain_save_config(gc, d_config, xc_config);
> @@ -771,9 +772,8 @@ static void initiate_domain_create(libxl__egc *egc,
>      libxl_domain_config *const d_config = dcs->guest_config;
>      libxl__domain_build_state *const state = &dcs->build_state;
>      const int restore_fd = dcs->restore_fd;
> -    memset(&dcs->build_state, 0, sizeof(dcs->build_state));
>  
> -    domid = 0;
> +    domid = dcs->domid_soft_reset;
>  
>      if (d_config->c_info.ssid_label) {
>          char *s = d_config->c_info.ssid_label;
> @@ -921,7 +921,7 @@ static void initiate_domain_create(libxl__egc *egc,
>              d_config->nics[i].devid = ++last_devid;
>      }
>  
> -    if (restore_fd >= 0) {
> +    if (restore_fd >= 0 || dcs->domid_soft_reset != INVALID_DOMID) {
>          LOG(DEBUG, "restoring, not running bootloader");
>          domcreate_bootloader_done(egc, &dcs->bl, 0);
>      } else  {
> @@ -994,7 +994,7 @@ static void domcreate_bootloader_done(libxl__egc *egc,
>      dcs->dmss.dm.callback = domcreate_devmodel_started;
>      dcs->dmss.callback = domcreate_devmodel_started;
>  
> -    if ( restore_fd < 0 ) {
> +    if (restore_fd < 0 && dcs->domid_soft_reset == INVALID_DOMID) {
>          rc = libxl__domain_build(gc, d_config, domid, state);
>          domcreate_rebuild_done(egc, dcs, rc);
>          return;
> @@ -1014,8 +1014,10 @@ static void domcreate_bootloader_done(libxl__egc *egc,
>      dcs->srs.completion_callback = domcreate_stream_done;
>      dcs->srs.checkpoint_callback = remus_checkpoint_stream_done;
>  
> -    libxl__stream_read_start(egc, &dcs->srs);
> -    return;
> +    if (restore_fd >= 0) {
> +        libxl__stream_read_start(egc, &dcs->srs);
> +        return;
> +    }
>  
>   out:
>      domcreate_stream_done(egc, &dcs->srs, rc);
> @@ -1094,8 +1096,12 @@ static void domcreate_stream_done(libxl__egc *egc,
>          goto out;
>  
>      if (info->type == LIBXL_DOMAIN_TYPE_HVM) {
> -        state->saved_state = GCSPRINTF(
> -                       XC_DEVICE_MODEL_RESTORE_FILE".%d", domid);
> +        if (fd != -1)
> +            state->saved_state = GCSPRINTF(
> +                XC_DEVICE_MODEL_RESTORE_FILE".%d", domid);
> +        else
> +            state->saved_state = GCSPRINTF(
> +                XC_DEVICE_MODEL_SAVE_FILE".%d", domid);
>      }
>  
>  out:
> @@ -1104,9 +1110,12 @@ out:
>          libxl__file_reference_unmap(&state->pv_ramdisk);
>      }
>  
> -    esave = errno;
> -    libxl_fd_set_nonblock(ctx, fd, 0);
> -    errno = esave;
> +    /* fd == -1 here means we're doing soft reset. */
> +    if (fd != -1) {
> +        esave = errno;
> +        libxl_fd_set_nonblock(ctx, fd, 0);
> +        errno = esave;
> +    }
>      domcreate_rebuild_done(egc, dcs, ret);
>  }
>  
> @@ -1527,6 +1536,14 @@ typedef struct {
>      uint32_t *domid_out;
>  } libxl__app_domain_create_state;
>  
> +typedef struct {
> +    libxl__app_domain_create_state cdcs;
> +    libxl__domain_destroy_state dds;
> +    libxl__domain_suspend_state dss;
> +    uint8_t *toolstack_buf;
> +    uint32_t toolstack_len;
> +} libxl__domain_soft_reset_state;
> +
>  static void domain_create_cb(libxl__egc *egc,
>                               libxl__domain_create_state *dcs,
>                               int rc, uint32_t domid);
> @@ -1549,6 +1566,7 @@ static int do_domain_create(libxl_ctx *ctx, libxl_domain_config *d_config,
>      if (restore_fd > -1)
>          cdcs->dcs.restore_params = *params;
>      cdcs->dcs.callback = domain_create_cb;
> +    cdcs->dcs.domid_soft_reset = INVALID_DOMID;
>      libxl__ao_progress_gethow(&cdcs->dcs.aop_console_how, aop_console_how);
>      cdcs->domid_out = domid;
>  
> @@ -1557,6 +1575,126 @@ static int do_domain_create(libxl_ctx *ctx, libxl_domain_config *d_config,
>      return AO_INPROGRESS;
>  }
>  
> +static void domain_soft_reset_cb(libxl__egc *egc,
> +                                 libxl__domain_destroy_state *dds,
> +                                 int rc)
> +{
> +    STATE_AO_GC(dds->ao);
> +    libxl__save_helper_state *shs;
> +    libxl__domain_soft_reset_state *srs = CONTAINER_OF(dds, *srs, dds);
> +    libxl__app_domain_create_state *cdcs = &srs->cdcs;
> +
> +    GCNEW(shs);
> +    shs->caller_state = &cdcs->dcs;
> +
> +    if (rc) {
> +        LOG(ERROR, "destruction of domain %u failed.", dds->domid);
> +        goto error;
> +    }
> +
> +    rc = libxl__toolstack_restore(cdcs->dcs.domid_soft_reset,
> +                                  srs->toolstack_buf,
> +                                  srs->toolstack_len, shs);
> +    if (rc) {
> +        LOG(ERROR, "failed to restore toolstack record.");
> +        goto error;
> +    }
> +
> +    initiate_domain_create(egc, &cdcs->dcs);
> +    return;
> +
> +error:
> +    domcreate_complete(egc, &cdcs->dcs, rc);
> +}
> +
> +static int do_domain_soft_reset(libxl_ctx *ctx,
> +                                libxl_domain_config *d_config,
> +                                uint32_t domid_soft_reset,
> +                                const libxl_asyncop_how *ao_how,
> +                                const libxl_asyncprogress_how
> +                                *aop_console_how)
> +{
> +    AO_CREATE(ctx, 0, ao_how);
> +    libxl__domain_soft_reset_state *srs;
> +    libxl__app_domain_create_state *cdcs;
> +    libxl__domain_create_state *dcs;
> +    libxl__domain_build_state *state;
> +    libxl__domain_suspend_state *dss;
> +    char *dom_path, *xs_store_mfn, *xs_console_mfn;
> +    uint32_t domid_out;
> +    int rc;
> +
> +    GCNEW(srs);
> +    cdcs = &srs->cdcs;
> +    dcs = &cdcs->dcs;
> +    state = &dcs->build_state;
> +    dss = &srs->dss;
> +
> +    srs->cdcs.dcs.ao = ao;
> +    srs->cdcs.dcs.guest_config = d_config;
> +    libxl_domain_config_init(&srs->cdcs.dcs.guest_config_saved);
> +    libxl_domain_config_copy(ctx, &srs->cdcs.dcs.guest_config_saved,
> +                             d_config);
> +    cdcs->dcs.restore_fd = -1;
> +    cdcs->dcs.domid_soft_reset = domid_soft_reset;
> +    cdcs->dcs.callback = domain_create_cb;
> +    libxl__ao_progress_gethow(&srs->cdcs.dcs.aop_console_how,
> +                              aop_console_how);
> +    cdcs->domid_out = &domid_out;
> +
> +    dom_path = libxl__xs_get_dompath(gc, domid_soft_reset);
> +    if (!dom_path) {
> +        LOG(ERROR, "failed to read domain path");
> +        return AO_CREATE_FAIL(ERROR_FAIL);
> +    }
> +
> +    xs_store_mfn = xs_read(ctx->xsh, XBT_NULL,
> +                           GCSPRINTF("%s/store/ring-ref", dom_path),
> +                           NULL);
> +    state->store_mfn = xs_store_mfn ? atol(xs_store_mfn): 0;
> +    free(xs_store_mfn);
> +
> +    xs_console_mfn = xs_read(ctx->xsh, XBT_NULL,
> +                             GCSPRINTF("%s/console/ring-ref", dom_path),
> +                             NULL);
> +    state->console_mfn = xs_console_mfn ? atol(xs_console_mfn): 0;
> +    free(xs_console_mfn);
> +
> +    dss->ao = ao;
> +    dss->domid = domid_soft_reset;
> +    dss->dm_savefile = GCSPRINTF(XC_DEVICE_MODEL_SAVE_FILE".%d",
> +                                 domid_soft_reset);
> +
> +    rc = libxl__toolstack_save(domid_soft_reset, &srs->toolstack_buf,
> +                               &srs->toolstack_len, dss);
> +    if (rc) {
> +        LOG(ERROR, "failed to save toolstack record.");
> +        return AO_CREATE_FAIL(ERROR_FAIL);
> +    }
> +
> +    rc = libxl__domain_suspend_device_model(gc, dss);
> +    if (rc) {
> +        LOG(ERROR, "failed to suspend device model.");
> +        return AO_CREATE_FAIL(ERROR_FAIL);
> +    }
> +
> +    /*
> +     * Ask all backends to disconnect by removing the domain from
> +     * xenstore. On the creation path the domain will be introduced to
> +     * xenstore again with probably different store/console/...
> +     * channels.
> +     */
> +    xs_release_domain(ctx->xsh, cdcs->dcs.domid_soft_reset);
> +
> +    srs->dds.ao = ao;
> +    srs->dds.domid = domid_soft_reset;
> +    srs->dds.callback = domain_soft_reset_cb;
> +    srs->dds.soft_reset = true;
> +    libxl__domain_destroy(egc, &srs->dds);
> +
> +    return AO_INPROGRESS;
> +}
> +
>  static void domain_create_cb(libxl__egc *egc,
>                               libxl__domain_create_state *dcs,
>                               int rc, uint32_t domid)
> @@ -1588,6 +1726,21 @@ int libxl_domain_create_restore(libxl_ctx *ctx, libxl_domain_config *d_config,
>                              ao_how, aop_console_how);
>  }
>  
> +int libxl_domain_soft_reset(libxl_ctx *ctx,
> +                            libxl_domain_config *d_config,
> +                            uint32_t domid,
> +                            const libxl_asyncop_how *ao_how,
> +                            const libxl_asyncprogress_how
> +                            *aop_console_how)
> +{
> +    libxl_domain_build_info *const info = &d_config->b_info;
> +
> +    if (info->type != LIBXL_DOMAIN_TYPE_HVM) return ERROR_INVAL;
> +
> +    return do_domain_soft_reset(ctx, d_config, domid, ao_how,
> +                                aop_console_how);
> +}
> +
>  /*
>   * Local variables:
>   * mode: C
> diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
> index f2466dc..352f087 100644
> --- a/tools/libxl/libxl_internal.h
> +++ b/tools/libxl/libxl_internal.h
> @@ -109,6 +109,7 @@
>  #define STUBDOM_SPECIAL_CONSOLES 3
>  #define TAP_DEVICE_SUFFIX "-emu"
>  #define DOMID_XS_PATH "domid"
> +#define INVALID_DOMID ~0
>  
>  #define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
>  
> @@ -3217,6 +3218,7 @@ struct libxl__destroy_domid_state {
>      /* private to implementation */
>      libxl__devices_remove_state drs;
>      libxl__ev_child destroyer;
> +    bool soft_reset;
>  };
>  
>  struct libxl__domain_destroy_state {
> @@ -3231,6 +3233,7 @@ struct libxl__domain_destroy_state {
>      int stubdom_finished;
>      libxl__destroy_domid_state domain;
>      int domain_finished;
> +    bool soft_reset;
>  };
>  
>  /*
> @@ -3394,6 +3397,7 @@ struct libxl__domain_create_state {
>      libxl_domain_config guest_config_saved; /* vanilla config */
>      int restore_fd, libxc_fd;
>      libxl_domain_restore_params restore_params;
> +    uint32_t domid_soft_reset;
>      libxl__domain_create_cb *callback;
>      libxl_asyncprogress_how aop_console_how;
>      /* private to domain_create */
> diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
> index 9f6ec00..87d8255 100644
> --- a/tools/libxl/libxl_types.idl
> +++ b/tools/libxl/libxl_types.idl
> @@ -138,6 +138,8 @@ libxl_action_on_shutdown = Enumeration("action_on_shutdown", [
>  
>      (5, "COREDUMP_DESTROY"),
>      (6, "COREDUMP_RESTART"),
> +
> +    (7, "SOFT_RESET"),
>      ], init_val = "LIBXL_ACTION_ON_SHUTDOWN_DESTROY")
>  
>  libxl_trigger = Enumeration("trigger", [
> diff --git a/tools/libxl/xl.h b/tools/libxl/xl.h
> index 6c19c0d..0021112 100644
> --- a/tools/libxl/xl.h
> +++ b/tools/libxl/xl.h
> @@ -194,6 +194,7 @@ typedef enum {
>      DOMAIN_RESTART_NONE = 0,     /* No domain restart */
>      DOMAIN_RESTART_NORMAL,       /* Domain should be restarted */
>      DOMAIN_RESTART_RENAME,       /* Domain should be renamed and restarted */
> +    DOMAIN_RESTART_SOFT_RESET,   /* Soft reset should be performed */
>  } domain_restart_type;
>  
>  extern void printf_info_sexp(int domid, libxl_domain_config *d_config, FILE *fh);
> diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
> index 2e9e1bd..0b29d34 100644
> --- a/tools/libxl/xl_cmdimpl.c
> +++ b/tools/libxl/xl_cmdimpl.c
> @@ -133,6 +133,8 @@ static const char *action_on_shutdown_names[] = {
>  
>      [LIBXL_ACTION_ON_SHUTDOWN_COREDUMP_DESTROY] = "coredump-destroy",
>      [LIBXL_ACTION_ON_SHUTDOWN_COREDUMP_RESTART] = "coredump-restart",
> +
> +    [LIBXL_ACTION_ON_SHUTDOWN_SOFT_RESET] = "soft-reset",
>  };
>  
>  /* Optional data, in order:
> @@ -1396,7 +1398,7 @@ static void parse_config_data(const char *config_source,
>      }
>  
>      if (xlu_cfg_get_string (config, "on_soft_reset", &buf, 0))
> -        buf = "restart";
> +        buf = "soft-reset";
>      if (!parse_action_on_shutdown(buf, &d_config->on_soft_reset)) {
>          fprintf(stderr, "Unknown on_soft_reset action \"%s\" specified\n", buf);
>          exit(1);
> @@ -2469,6 +2471,11 @@ static domain_restart_type handle_domain_death(uint32_t *r_domid,
>          *r_domid = INVALID_DOMID;
>          break;
>  
> +    case LIBXL_ACTION_ON_SHUTDOWN_SOFT_RESET:
> +        reload_domain_config(*r_domid, d_config);
> +        restart = DOMAIN_RESTART_SOFT_RESET;
> +        break;
> +
>      case LIBXL_ACTION_ON_SHUTDOWN_COREDUMP_DESTROY:
>      case LIBXL_ACTION_ON_SHUTDOWN_COREDUMP_RESTART:
>          /* Already handled these above. */
> @@ -2644,6 +2651,7 @@ static uint32_t create_domain(struct domain_create *dom_info)
>      int restore_fd = -1;
>      const libxl_asyncprogress_how *autoconnect_console_how;
>      struct save_file_header hdr;
> +    uint32_t domid_soft_reset = INVALID_DOMID;
>  
>      int restoring = (restore_file || (migrate_fd >= 0));
>  
> @@ -2857,7 +2865,13 @@ start:
>           * restore/migrate-receive it again.
>           */
>          restoring = 0;
> -    }else{
> +    } else if ( domid_soft_reset != INVALID_DOMID ) {
> +        /* Do soft reset. */
> +        ret = libxl_domain_soft_reset(ctx, &d_config, domid_soft_reset,
> +                                      0, autoconnect_console_how);
> +        domid = domid_soft_reset;
> +        domid_soft_reset = INVALID_DOMID;
> +    } else {
>          ret = libxl_domain_create_new(ctx, &d_config, &domid,
>                                        0, autoconnect_console_how);
>      }
> @@ -2918,8 +2932,13 @@ start:
>                  event->u.domain_shutdown.shutdown_reason,
>                  event->u.domain_shutdown.shutdown_reason);
>              switch (handle_domain_death(&domid, event, &d_config)) {
> +            case DOMAIN_RESTART_SOFT_RESET:
> +                domid_soft_reset = domid;
> +                domid = INVALID_DOMID;
> +                /* fall through */
>              case DOMAIN_RESTART_RENAME:
> -                if (!preserve_domain(&domid, event, &d_config)) {
> +                if (domid_soft_reset == INVALID_DOMID &&
> +                    !preserve_domain(&domid, event, &d_config)) {
>                      /* If we fail then exit leaving the old domain in place. */
>                      ret = -1;
>                      goto out;
> -- 
> 2.4.3
>