Re: [Xen-devel] [PATCH 05 of 16 RFC] blktap3: Don't check if blktap is available

[Thanos Makatos <thanos.makatos@xxxxxxxxxx>]

> -----Original Message-----
> From: Ian Campbell
> Sent: 26 October 2012 12:24
> To: Thanos Makatos
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-devel] [PATCH 05 of 16 RFC] blktap3: Don't check if
> blktap is available
> 
> On Wed, 2012-10-24 at 18:02 +0100, Thanos Makatos wrote:
> > Don't check if blktap is enabled since it will always be enabled (no
> > blktap/blkback requirement anymore).
> 
> I think this needs to stay until the *BSD dom0's implement the
> necessary kernel drivers (gnttab/gntalloc etc) such that blktap3 can
> run on them.
> Currently we use libxl_noblktap2.c on those platforms and I think until
> then we need to retain a libxl_noblktap3.c for use there.

Ok.

> 
> Perhaps even on Linux we would want a sanity check that the drivers are
> present and loaded etc?

We could ensure that the tapdisk binaries are present, apart from that I don't 
see anything else we could check.

> 
> >
> > diff -r bcb5a6182868 -r 57896068356d tools/libxl/libxl_blktap3.c
> > --- a/tools/libxl/libxl_blktap3.c   Wed Oct 24 17:25:02 2012 +0100
> > +++ b/tools/libxl/libxl_blktap3.c   Wed Oct 24 17:25:12 2012 +0100
> > @@ -1,10 +1,6 @@
> >  #include "libxl_osdeps.h"
> >  #include "libxl_internal.h"
> >
> > -int libxl__blktap_enabled(libxl__gc *gc) {
> > -    return 1;
> > -}
> > -
> >  int libxl__blktap_devpath(libxl__gc *gc, const char *disk,
> >      libxl_disk_format format) {
> >      return -ENOSYS;
> > diff -r bcb5a6182868 -r 57896068356d tools/libxl/libxl_device.c
> > --- a/tools/libxl/libxl_device.c    Wed Oct 24 17:25:02 2012 +0100
> > +++ b/tools/libxl/libxl_device.c    Wed Oct 24 17:25:12 2012 +0100
> > @@ -177,13 +177,6 @@ static int disk_try_backend(disk_try_bac
> >
> >      case LIBXL_DISK_BACKEND_TAP:
> >          if (a->disk->script) goto bad_script;
> > -
> > -        if (!libxl__blktap_enabled(a->gc)) {
> > -            LIBXL__LOG(ctx, LIBXL__LOG_DEBUG, "Disk vdev=%s, backend
> tap"
> > -                       " unsuitable because blktap not available",
> > -                       a->disk->vdev);
> > -            return 0;
> > -        }
> >          if (!(a->disk->format == LIBXL_DISK_FORMAT_RAW ||
> >                a->disk->format == LIBXL_DISK_FORMAT_VHD)) {
> >              goto bad_format;
> >
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> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel
> 

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