Re: arch/arm64/kernel/topology.c:367:22: sparse: sparse: dereference of noderef expression

Catalin Marinas
2020-12-18T10:44:56Z

On Fri, Dec 18, 2020 at 05:00:16AM +0800, kernel test robot wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head: 74f602dc96dd854c7b2034947798c1e2a6b84066
> commit: 68c5debcc06d6d24f15dbf978780fc5efc147d5e arm64: implement CPPC FFH support using AMUs
> date: 5 weeks ago
> config: arm64-randconfig-s032-20201217 (attached as .config)
> compiler: aarch64-linux-gcc (GCC) 9.3.0
> reproduce:
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # apt-get install sparse
> # sparse version: v0.6.3-184-g1b896707-dirty
> # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=68c5debcc06d6d24f15dbf978780fc5efc147d5e
> git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> git fetch --no-tags linus master
> git checkout 68c5debcc06d6d24f15dbf978780fc5efc147d5e
> # save the attached .config to linux build tree
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=arm64
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
>
> "sparse warnings: (new ones prefixed by >>)"
> >> arch/arm64/kernel/topology.c:367:22: sparse: sparse: dereference of noderef expression
>
> vim +367 arch/arm64/kernel/topology.c
>
> 362
> 363 int cpc_read_ffh(int cpu, struct cpc_reg *reg, u64 *val)
> 364 {
> 365 int ret = -EOPNOTSUPP;
> 366
> > 367 switch ((u64)reg->address) {

That's not a dereference but I guess sparse complains of dropping the
__iomem. We could change the cast to (__force u64) to silence sparse.

Thanks for the report.

--
Catalin