Hi Thomas,

First bad commit (maybe != root cause):

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git irq/core
head:   3bda84519c6c2d57e7378417ac116f61d50abae1
commit: f07147b162a1cec348d8a9a7e7e73fdf7ce5f88b [56/60] genirq: Remove export of irq_to_desc()
config: powerpc-allmodconfig (attached as .config)
compiler: powerpc64-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=f07147b162a1cec348d8a9a7e7e73fdf7ce5f88b
        git remote add tip https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
        git fetch --no-tags tip irq/core
        git checkout f07147b162a1cec348d8a9a7e7e73fdf7ce5f88b
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=powerpc 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>, old ones prefixed by <<):

ERROR: modpost: ".__irq_set_lockdep_class" [drivers/spmi/spmi-pmic-arb.ko] undefined!
ERROR: modpost: ".__irq_set_lockdep_class" [drivers/net/dsa/mv88e6xxx/mv88e6xxx.ko] undefined!
ERROR: modpost: ".__irq_set_lockdep_class" [drivers/gpio/gpio-brcmstb.ko] undefined!
ERROR: modpost: ".__irq_set_lockdep_class" [drivers/pinctrl/pinctrl-single.ko] undefined!
>> ERROR: modpost: ".irq_to_desc" [arch/powerpc/kvm/kvm-hv.ko] undefined!

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0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org