Hi Christoph,

First bad commit (maybe != root cause):

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   0dc589da873b58b70f4caf4b070fb0cf70fdd1dc
commit: cc97923a5bccc776851c242b61015faf288d5c22 block: move dma drain handling to scsi
date:   3 months ago
config: microblaze-randconfig-r011-20200714 (attached as .config)
compiler: microblaze-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
        git checkout cc97923a5bccc776851c242b61015faf288d5c22
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=microblaze 

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: "min_low_pfn" [drivers/rpmsg/virtio_rpmsg_bus.ko] undefined!
ERROR: modpost: "min_low_pfn" [drivers/mtd/nand/raw/cadence-nand-controller.ko] undefined!
>> ERROR: modpost: "min_low_pfn" [drivers/scsi/scsi_mod.ko] undefined!
ERROR: modpost: "min_low_pfn" [security/keys/encrypted-keys/encrypted-keys.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