Re: [Xen-devel] [RFC 7/7] libxl: Wait for QEMU startup in stubdomain

[Wei Liu <wei.liu2@xxxxxxxxxx>]

Thanks for posting.

On Tue, Feb 03, 2015 at 11:06:15PM -0500, Eric Shelton wrote:
[...]
> @@ -1368,12 +1401,24 @@ static void stubdom_pvqemu_cb(libxl__egc *egc,
>      libxl__stub_dm_spawn_state *sdss = CONTAINER_OF(multidev, *sdss, 
> multidev);
>      STATE_AO_GC(sdss->dm.spawn.ao);
>      uint32_t dm_domid = sdss->pvqemu.guest_domid;
> +    libxl__xswait_state *xswait = &sdss->pvqemu.spawn.xswait;
>  
>      if (rc) {
>          LOGE(ERROR, "error connecting nics devices");
>          goto out;
>      }
>  
> +    /* wait for PV stubdom QEMU instance to be ready */
> +    libxl__xswait_init(xswait);
> +    xswait->ao = sdss->dm.spawn.ao;
> +    xswait->what = GCSPRINTF("stub domain %d startup", dm_domid);
> +    xswait->path = GCSPRINTF("/local/domain/0/device-model/%d/state",
> +                             sdss->dm.guest_domid);

FWIW  we are now experiencing problem with this startup protocol (not
Linux stubdom specific) -- that path that libxl waiting for is wrong.

Unfortunately this problem can't be solved without putting in
significant effort and time (involves redesign of protocol and handle
all the compatibility issues). We can't say for sure when the solution
is going to land.

Also upstream QEMU stubdom, as you already notice, doesn't have a
critical functionality -- save / restore. Adding that in might involve
upstreaming some changes to QEMU, which has a time frame that is out of
our control.  So my hunch is that we're not going to make it in time for
4.6. :-/

Wei.

> +    xswait->timeout_ms = LIBXL_DEVICE_MODEL_START_TIMEOUT * 1000;
> +    xswait->callback = stub_dm_watch_event;
> +    rc = libxl__xswait_start(gc, xswait);
> +    if (rc) goto out;
> +
>      rc = libxl_domain_unpause(CTX, dm_domid);
>      if (rc) goto out;
>  
> @@ -1387,7 +1432,6 @@ static void stubdom_pvqemu_cb(libxl__egc *egc,
>              return;
>          }
>      }
> -    sdss->callback(egc, &sdss->dm, rc);
>  }
>  
>  static void spawn_stubdom_pvqemu_destroy_cb(libxl__egc *egc,
> -- 
> 1.8.5.5
> 
> 
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