Re: [PATCH v3 04/17] libxl: Allow running qemu-xen in stubdomain

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Thu, Feb 21, 2019 at 04:01:59PM +0000, Wei Liu wrote:
> On Mon, Jan 28, 2019 at 10:30:21PM +0100, Marek Marczykowski-Górecki wrote:
> > Do not prohibit anymore using stubdomain with qemu-xen.
> > To help distingushing MiniOS and Linux stubdomain, add helper inline
> > functions libxl__stubdomain_is_linux() and
> > libxl__stubdomain_is_linux_running(). Those should be used where really
> > the difference is about MiniOS/Linux, not qemu-xen/qemu-xen-traditional.
> > 
> > Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
> > 
> > ---
> > Changes in v3:
> >  - new patch, instead of "libxl: Add "stubdomain_version" to
> >  domain_build_info"
> >  - helper functions as suggested by Ian Jackson
> > ---
> >  tools/libxl/libxl_create.c   |  9 ---------
> >  tools/libxl/libxl_internal.h | 17 +++++++++++++++++
> >  2 files changed, 17 insertions(+), 9 deletions(-)
> > 
(...)
> > diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
> > index 459f9bf..b8c698a 100644
> > --- a/tools/libxl/libxl_internal.h
> > +++ b/tools/libxl/libxl_internal.h
> > @@ -2195,6 +2195,23 @@ _hidden int libxl__device_model_version_running(libxl__gc *gc, uint32_t domid);
> >    /* Return the system-wide default device model */
> >  _hidden libxl_device_model_version libxl__default_device_model(libxl__gc *gc);
> >  
> > +static inline
> > +bool libxl__stubdomain_is_linux_running(libxl__gc *gc, uint32_t domid)
> > +{
> > +    /* same logic as in libxl__stubdomain_is_linux */
> > +    return libxl__device_model_version_running(gc, domid)
> > +        == LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN;
> 
> I don't think the logic is accurate. You're precluding running
> qemu-xen in a unikernel as stubdom.
> 
> I think putting an extra key in xenstore with the underlying platform is
> more desirable.
> 
> > +}
> > +
> > +static inline
> > +bool libxl__stubdomain_is_linux(libxl_domain_build_info *b_info)
> > +{
> > +    /* right now qemu-tranditional implies MiniOS stubdomain and qemu-xen
> > +     * implies Linux stubdomain */
> > +    return libxl_defbool_val(b_info->device_model_stubdomain) &&
> > +        b_info->device_model_version == LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN;
> 
> Subsequently you will need a new field in b_info.
> 
> What do you think?

This is _exactly_ what was in v2 of this patch and Ian suggested to
change it:
https://lists.xenproject.org/archives/html/xen-devel/2018-10/msg01317.html

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

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