Re: [Xen-devel] Xen 4.6 script calling conventions

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Jul 04, 2016 at 01:57:20PM +0200, Roger Pau Monné wrote:
> 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@xxxxxxxxxx>
> > 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@xxxxxxxxx>
> > Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> > ---
> >  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@xxxxxxxxxx>
> 

Thanks for your clarification on how netbsd works.

I will update the patch accordingly.

Wei.

> Thanks, Roger.

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