Re: [Xen-devel] [PATCH] xen: Kconfig: Add DEBUG_XEN config option

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Feb 01, 2017 at 02:12:13PM +0100, Juergen Gross wrote:
> On 01/02/17 13:55, Julien Grall wrote:
> > Hi Juergen,
> > 
> > On 01/02/2017 12:17, Juergen Gross wrote:
> >> On 01/02/17 12:19, Andrii Anisov wrote:
> >>> From: Andrii Anisov <andrii_anisov@xxxxxxxx>
> >>>
> >>> Add a debug option to enable xen drivers debug code.
> >>>
> >>> Signed-off-by: Andrii Anisov <andrii_anisov@xxxxxxxx>
> >>
> >> In future you might want to add the maintainers to the recipient list.
> >>
> >>> ---
> >>>  drivers/xen/Kconfig  | 8 ++++++++
> >>>  drivers/xen/Makefile | 2 ++
> >>>  2 files changed, 10 insertions(+)
> >>>
> >>> diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
> >>> index f15bb3b7..733c433 100644
> >>> --- a/drivers/xen/Kconfig
> >>> +++ b/drivers/xen/Kconfig
> >>> @@ -298,4 +298,12 @@ config XEN_SYMS
> >>>  config XEN_HAVE_VPMU
> >>>         bool
> >>>
> >>> +config DEBUG_XEN
> >>> +    bool "XEN Drivers debug"
> >>> +    depends on DEBUG_KERNEL
> >>> +    help
> >>> +      Say Y here if you want to enable XEN drivers debug code.
> >>> +
> >>> +      If you are unsure about this, say N here.
> >>
> >> So is this really a sensible thing to do? I don't see the value for
> >> such a global config option possibly switching so many different
> >> drivers to debug mode.
> >>
> >> In reality you want to do something like "debug" for a single driver
> >> only during time of development. This won't need a global config
> >> option but just a "#define" in the driver which is active while
> >> developing and testing and which should be removed or commented out
> >> when the final submission of the driver is done.
> > 
> > This Kconfig was suggested in the context of [1]. The number of people
> > working on swiotlb is very limited, but the check added is really useful
> > in debug build to catch potential misuse for anyone.
> > 
> > Do you have any other idea to turn this check on for debug build??
> 
> I think for this use case we would want either a more specific config
> option name (e.g. DEBUG_XEN_SWIOTLB) or a more specific description
> what it is doing, like e.g.:

I really don't want to add this in the Xen SWIOTLB.

It is kind of pointless - I would prefer if the debug code had
just #if 0 with a comment explaining why it is such and what it
can be used for.

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