Re: [Xen-devel] [PATCH v4 12/24] xen/arm: introduce CONFIG_XEN on ARM

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 17 Sep 2012, Stefano Stabellini wrote:
> On Mon, 17 Sep 2012, Sergei Shtylyov wrote:
> > Hello.
> > 
> > On 17-09-2012 14:57, Stefano Stabellini wrote:
> > 
> > >>> Changes in v2:
> > 
> > >>> - mark Xen guest support on ARM as EXPERIMENTAL.
> > 
> > >>> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > >>> Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > >>> ---
> > >>>   arch/arm/Kconfig |   10 ++++++++++
> > >>>   1 files changed, 10 insertions(+), 0 deletions(-)
> > 
> > >>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > >>> index 2f88d8d..e92518d 100644
> > >>> --- a/arch/arm/Kconfig
> > >>> +++ b/arch/arm/Kconfig
> > >>> @@ -1897,6 +1897,16 @@ config DEPRECATED_PARAM_STRUCT
> > >>>           This was deprecated in 2001 and announced to live on for 5 
> > >>> years.
> > >>>           Some old boot loaders still use this way.
> > >>>
> > >>> +config XEN_DOM0
> > >>> +       def_bool y
> > >>> +
> > >>> +config XEN
> > >>> +       bool "Xen guest support on ARM (EXPERIMENTAL)"
> > >>> +       depends on EXPERIMENTAL && ARM && OF
> > >>> +       select XEN_DOM0
> > 
> > >>     What's the point of selecting it if it's always "y"?
> > 
> > > That's because on X86 is not always "y": there are things under
> > > drivers/xen that compile on both platforms and depend on XEN_DOM0.
> > 
> >     But we're not on x86. On ARM this select is pointless.
> 
> We need some common code (under drivers/xen) that compiles only if
> XEN_DOM0 is selected, so it is not pointless after all.
> 
> XEN_DOM0 is not the only symbol that is conditionally compiled on one
> architectuire and always "y" on another...
> 

Wait a sec, I have just realized that written this way XEN_DOM0 is
always "y", even if XEN is not!
The right way of doing this is:


config XEN_DOM0
        def_bool y
        depends on XEN

config XEN
        bool "Xen guest support on ARM (EXPERIMENTAL)"
        depends on EXPERIMENTAL && ARM && OF
        help
          Say Y if you want to run Linux in a Virtual Machine on Xen on ARM.


I am not sure if this is what you meant, but thanks for making me
realize this mistake anyway! :)

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