Re: Xen 4.6 script calling conventions

["Roger Pau Monné" <roger.pau@citrix.com>]

On Sat, Jul 02, 2016 at 12:40:43PM +0100, Wei Liu wrote:
> On Tue, Jun 28, 2016 at 06:00:49PM -0700, John Nemeth wrote:
> >      I'm trying to package Xen 4.6 (specifically Xen 4.6.3) for
> > use with NetBSD.  I have it mostly done; however, when I try to
> > create a domU, libxl goes into an infinite loop calling the scripts.
> > If I try to create a domU with no network or disk, it works fine
> > (albeit of rather limited use).  Have there been changes between
> > Xen 4.5 and Xen 4.6 in the calling convention for the scripts?  Is
> > there documentation on what is expected somewhere?  Please CC me on
> > any responses.  Here is my domU config file:
> 
> Can you give this patch a try? I don't have netbsd system at hand to
> test it.
> 
> I suspect netbsd doesn't support stubdom because that pile of code is a
> bit Linux centric, but it wouldn't hurt to prepare for it.
> 
> ---8<---
> From 3c64a22f4a5dcf76244c2acff7a26717402ea33c Mon Sep 17 00:00:00 2001
> From: Wei Liu <wei.liu2@citrix.com>
> Date: Sat, 2 Jul 2016 12:35:30 +0100
> Subject: [PATCH] libxl/netbsd: check num_exec in hotplug function
> 
> This basically replicates the same logic in libxl_linux.c. Without this
> libxl will loop indefinitely trying to execute hotplug script.
> 
> Reported-by: John Nemeth <jnemeth@cue.bc.ca>
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> ---
>  tools/libxl/libxl_netbsd.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/tools/libxl/libxl_netbsd.c b/tools/libxl/libxl_netbsd.c
> index 096c057..92d3c89 100644
> --- a/tools/libxl/libxl_netbsd.c
> +++ b/tools/libxl/libxl_netbsd.c
> @@ -68,7 +68,25 @@ int libxl__get_hotplug_script_info(libxl__gc *gc, libxl__device *dev,
>  
>      switch (dev->backend_kind) {
>      case LIBXL__DEVICE_KIND_VBD:
> +        if (num_exec != 0) {
> +            LOG(DEBUG, "num_exec %d, not running hotplug scripts", num_exec);
> +            rc = 0;
> +            goto out;
> +        }
> +        rc = libxl__hotplug(gc, dev, args, action);
> +        if (!rc) rc = 1;
> +        break;
>      case LIBXL__DEVICE_KIND_VIF:
> +        /*
> +         * If domain has a stubdom we don't have to execute hotplug scripts
> +         * for emulated interfaces
> +         */
> +        if ((num_exec > 1) ||

This should be num_exec != 0, NetBSD libxl only executes the network hotplug 
script once, because the emulated network card is attached to the bridge 
using a script called directly by QEMU, see:

http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=tools/libxl/libxl_dm.c;hb=HEAD#l608

And:

http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=tools/libxl/libxl_dm.c;hb=HEAD#l27 

Apart from that the change looks fine, and provided this is fixed:

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks, Roger.

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