Re: [xen-tip:linux-next 12/12] WARNING: modpost: vmlinux: section mismatch in reference: mc_debug_data+0x0 (section: .data) -> mc_debug_data_early (section: .init.data)

[Jürgen Groß <jgross@xxxxxxxx>]

On 24.07.24 08:54, Jan Beulich wrote:
> On 24.07.2024 08:07, Juergen Gross wrote:
> > On 24.07.24 03:08, kernel test robot wrote:
> > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git linux-next
> > > head:   368990a7fe30737c990f628a60d26d9854a9e690
> > > commit: 368990a7fe30737c990f628a60d26d9854a9e690 [12/12] xen: fix multicall 
> > > debug data referencing
> > > config: x86_64-randconfig-012-20240724 
> > > (https://download.01.org/0day-ci/archive/20240724/202407240907.u0NJHgTu-lkp@xxxxxxxxx/config)
> > > compiler: gcc-13 (Ubuntu 13.2.0-4ubuntu3) 13.2.0
> > > reproduce (this is a W=1 build): 
> > > (https://download.01.org/0day-ci/archive/20240724/202407240907.u0NJHgTu-lkp@xxxxxxxxx/reproduce)
> > >
> > > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > > the same patch/commit), kindly add following tags
> > > | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > > | Closes: 
> > > https://lore.kernel.org/oe-kbuild-all/202407240907.u0NJHgTu-lkp@xxxxxxxxx/
> > >
> > > All warnings (new ones prefixed by >>, old ones prefixed by <<):
> > >
> > > > > WARNING: modpost: vmlinux: section mismatch in reference: mc_debug_data+0x0 
> > > > > (section: .data) -> mc_debug_data_early (section: .init.data)
> > With current infrastructure this is not easily fixable, as there is no way
> > to tag a percpu variable as __refdata.
> Would it be an option to drop the static initializer and set CPU0's value
> from xen_parse_mc_debug()?
It would hide this warning, yes.

OTOH I have another patch pending which will have the same problem, and this
time the solution would be more ugly, as the code would always be active in
a PV guest (yes, I could add an init function called very early during boot,
but ...).

I'd prefer a general way to handle this problem, like e.g. some kind of
__refdata tagging for percpu variables.


Juergen