Re: [PATCH v8 2/2] s390x: KVM: resetting the Topology-Change-Report

[kernel test robot <lkp@intel.com>]

Hi Pierre,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on kvm/master]
[also build test WARNING on v5.18-rc3]
[cannot apply to kvms390/next mst-vhost/linux-next next-20220420]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/intel-lab-lkp/linux/commits/Pierre-Morel/s390x-KVM-CPU-Topology/20220420-194302
base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git master
config: s390-randconfig-r044-20220420 (https://download.01.org/0day-ci/archive/20220420/202204202111.vLX6pMo0-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project bac6cd5bf85669e3376610cfc4c4f9ca015e7b9b)
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
        # install s390 cross compiling tool for clang build
        # apt-get install binutils-s390x-linux-gnu
        # https://github.com/intel-lab-lkp/linux/commit/0bdeef651636ac2ef4918fb6e3230614e2fb3581
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Pierre-Morel/s390x-KVM-CPU-Topology/20220420-194302
        git checkout 0bdeef651636ac2ef4918fb6e3230614e2fb3581
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash arch/s390/kvm/

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

All warnings (new ones prefixed by >>):

   In file included from arch/s390/kvm/kvm-s390.c:22:
   In file included from include/linux/kvm_host.h:41:
   In file included from include/linux/kvm_para.h:5:
   In file included from include/uapi/linux/kvm_para.h:37:
   In file included from arch/s390/include/asm/kvm_para.h:25:
   In file included from arch/s390/include/asm/diag.h:12:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:31:
   In file included from include/linux/dma-mapping.h:10:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:75:
   include/asm-generic/io.h:464:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __raw_readb(PCI_IOBASE + addr);
                             ~~~~~~~~~~ ^
   include/asm-generic/io.h:477:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/big_endian.h:37:59: note: expanded from macro '__le16_to_cpu'
   #define __le16_to_cpu(x) __swab16((__force __u16)(__le16)(x))
                                                             ^
   include/uapi/linux/swab.h:102:54: note: expanded from macro '__swab16'
   #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x))
                                                        ^
   In file included from arch/s390/kvm/kvm-s390.c:22:
   In file included from include/linux/kvm_host.h:41:
   In file included from include/linux/kvm_para.h:5:
   In file included from include/uapi/linux/kvm_para.h:37:
   In file included from arch/s390/include/asm/kvm_para.h:25:
   In file included from arch/s390/include/asm/diag.h:12:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:31:
   In file included from include/linux/dma-mapping.h:10:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:75:
   include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/big_endian.h:35:59: note: expanded from macro '__le32_to_cpu'
   #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
                                                             ^
   include/uapi/linux/swab.h:115:54: note: expanded from macro '__swab32'
   #define __swab32(x) (__u32)__builtin_bswap32((__u32)(x))
                                                        ^
   In file included from arch/s390/kvm/kvm-s390.c:22:
   In file included from include/linux/kvm_host.h:41:
   In file included from include/linux/kvm_para.h:5:
   In file included from include/uapi/linux/kvm_para.h:37:
   In file included from arch/s390/include/asm/kvm_para.h:25:
   In file included from arch/s390/include/asm/diag.h:12:
   In file included from include/linux/if_ether.h:19:
   In file included from include/linux/skbuff.h:31:
   In file included from include/linux/dma-mapping.h:10:
   In file included from include/linux/scatterlist.h:9:
   In file included from arch/s390/include/asm/io.h:75:
   include/asm-generic/io.h:501:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writeb(value, PCI_IOBASE + addr);
                               ~~~~~~~~~~ ^
   include/asm-generic/io.h:511:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   include/asm-generic/io.h:521:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   include/asm-generic/io.h:609:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           readsb(PCI_IOBASE + addr, buffer, count);
                  ~~~~~~~~~~ ^
   include/asm-generic/io.h:617:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           readsw(PCI_IOBASE + addr, buffer, count);
                  ~~~~~~~~~~ ^
   include/asm-generic/io.h:625:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           readsl(PCI_IOBASE + addr, buffer, count);
                  ~~~~~~~~~~ ^
   include/asm-generic/io.h:634:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           writesb(PCI_IOBASE + addr, buffer, count);
                   ~~~~~~~~~~ ^
   include/asm-generic/io.h:643:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           writesw(PCI_IOBASE + addr, buffer, count);
                   ~~~~~~~~~~ ^
   include/asm-generic/io.h:652:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           writesl(PCI_IOBASE + addr, buffer, count);
                   ~~~~~~~~~~ ^
>> arch/s390/kvm/kvm-s390.c:1773:6: warning: variable 'val' set but not used [-Wunused-but-set-variable]
           int val;
               ^
   13 warnings generated.


vim +/val +1773 arch/s390/kvm/kvm-s390.c

  1758	
  1759	/**
  1760	 * kvm_s390_sca_clear_mtcr
  1761	 * @kvm: guest KVM description
  1762	 *
  1763	 * Is only relevant if the topology facility is present,
  1764	 * the caller should check KVM facility 11
  1765	 *
  1766	 * Updates the Multiprocessor Topology-Change-Report to signal
  1767	 * the guest with a topology change.
  1768	 */
  1769	static int kvm_s390_sca_clear_mtcr(struct kvm *kvm)
  1770	{
  1771		struct bsca_block *sca = kvm->arch.sca;
  1772		struct kvm_vcpu *vcpu;
> 1773		int val;
  1774	
  1775		vcpu = kvm_s390_get_first_vcpu(kvm);
  1776		if (!vcpu)
  1777			return -ENODEV;
  1778	
  1779		ipte_lock(vcpu);
  1780		val = READ_ONCE(sca->utility);
  1781		WRITE_ONCE(sca->utility, sca->utility & ~SCA_UTILITY_MTCR);
  1782		ipte_unlock(vcpu);
  1783	
  1784		return 0;
  1785	}
  1786	

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