So I guess kvm platforms that don't set KVM_ARCH_WANT_MMU_NOTIFIER exist, and at least on powerpc they're consistent with KVM_CAP_SYNC_MMU signalling that the guest pagetables stays in sync automatically with any updates. So for that case I guess we could use unsafe_follow_pfn.
But on s390 this seems different: No mmu notifier, but KVM_CAP_SYNC_MMU is set. So I guess there's some hardware magic on s390 that I don't know about. Not sure what to do with this now here ... -Daniel On Sat, Nov 28, 2020 at 03:10:40AM +0800, kernel test robot wrote: > Hi Daniel, > > I love your patch! Yet something to improve: > > [auto build test ERROR on linuxtv-media/master] > [also build test ERROR on char-misc/char-misc-testing v5.10-rc5] > [cannot apply to hnaz-linux-mm/master next-20201127] > [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/0day-ci/linux/commits/Daniel-Vetter/follow_pfn-and-other-iomap-races/20201128-004421 > base: git://linuxtv.org/media_tree.git master > config: s390-randconfig-r032-20201127 (attached as .config) > compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project > f095ac11a9550530a4a54298debb8b04b36422be) > 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/0day-ci/linux/commit/d76a3489433ce67d45da86aa12953385427f0ac9 > git remote add linux-review https://github.com/0day-ci/linux > git fetch --no-tags linux-review > Daniel-Vetter/follow_pfn-and-other-iomap-races/20201128-004421 > git checkout d76a3489433ce67d45da86aa12953385427f0ac9 > # save the attached .config to linux build tree > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=s390 > > If you fix the issue, kindly add following tag as appropriate > Reported-by: kernel test robot <l...@intel.com> > > All errors (new ones prefixed by >>): > > 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:80: > 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:34:59: note: expanded from macro > '__le32_to_cpu' > #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x)) > ^ > include/uapi/linux/swab.h:119:21: note: expanded from macro '__swab32' > ___constant_swab32(x) : \ > ^ > include/uapi/linux/swab.h:21:12: note: expanded from macro > '___constant_swab32' > (((__u32)(x) & (__u32)0x00ff0000UL) >> 8) | \ > ^ > In file included from arch/s390/kvm/../../../virt/kvm/kvm_main.c:18: > In file included from include/linux/kvm_host.h:32: > In file included from include/linux/kvm_para.h:5: > In file included from include/uapi/linux/kvm_para.h:36: > 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:80: > 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:34:59: note: expanded from macro > '__le32_to_cpu' > #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x)) > ^ > include/uapi/linux/swab.h:119:21: note: expanded from macro '__swab32' > ___constant_swab32(x) : \ > ^ > include/uapi/linux/swab.h:22:12: note: expanded from macro > '___constant_swab32' > (((__u32)(x) & (__u32)0xff000000UL) >> 24))) > ^ > In file included from arch/s390/kvm/../../../virt/kvm/kvm_main.c:18: > In file included from include/linux/kvm_host.h:32: > In file included from include/linux/kvm_para.h:5: > In file included from include/uapi/linux/kvm_para.h:36: > 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:80: > 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:34:59: note: expanded from macro > '__le32_to_cpu' > #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x)) > ^ > include/uapi/linux/swab.h:120:12: note: expanded from macro '__swab32' > __fswab32(x)) > ^ > In file included from arch/s390/kvm/../../../virt/kvm/kvm_main.c:18: > In file included from include/linux/kvm_host.h:32: > In file included from include/linux/kvm_para.h:5: > In file included from include/uapi/linux/kvm_para.h:36: > 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:80: > 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/../../../virt/kvm/kvm_main.c:1894:40: error: no member named > >> 'mmu_notifier' in 'struct kvm' > r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier); > ~~~ ^ > arch/s390/kvm/../../../virt/kvm/kvm_main.c:1909:41: error: no member named > 'mmu_notifier' in 'struct kvm' > r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier); > ~~~ ^ > 20 warnings and 2 errors generated. > > vim +1894 arch/s390/kvm/../../../virt/kvm/kvm_main.c > > 1885 > 1886 static int hva_to_pfn_remapped(struct kvm *kvm, struct > vm_area_struct *vma, > 1887 unsigned long addr, bool *async, > 1888 bool write_fault, bool *writable, > 1889 kvm_pfn_t *p_pfn) > 1890 { > 1891 unsigned long pfn; > 1892 int r; > 1893 > > 1894 r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier); > 1895 if (r) { > 1896 /* > 1897 * get_user_pages fails for VM_IO and VM_PFNMAP > vmas and does > 1898 * not call the fault handler, so do it here. > 1899 */ > 1900 bool unlocked = false; > 1901 r = fixup_user_fault(current->mm, addr, > 1902 (write_fault ? > FAULT_FLAG_WRITE : 0), > 1903 &unlocked); > 1904 if (unlocked) > 1905 return -EAGAIN; > 1906 if (r) > 1907 return r; > 1908 > 1909 r = follow_pfn(vma, addr, &pfn, > &kvm->mmu_notifier); > 1910 if (r) > 1911 return r; > 1912 > 1913 } > 1914 > 1915 if (writable) > 1916 *writable = true; > 1917 > 1918 /* > 1919 * Get a reference here because callers of *hva_to_pfn* > and > 1920 * *gfn_to_pfn* ultimately call kvm_release_pfn_clean > on the > 1921 * returned pfn. This is only needed if the VMA has > VM_MIXEDMAP > 1922 * set, but the kvm_get_pfn/kvm_release_pfn_clean pair > will > 1923 * simply do nothing for reserved pfns. > 1924 * > 1925 * Whoever called remap_pfn_range is also going to call > e.g. > 1926 * unmap_mapping_range before the underlying pages are > freed, > 1927 * causing a call to our MMU notifier. > 1928 */ > 1929 kvm_get_pfn(pfn); > 1930 > 1931 *p_pfn = pfn; > 1932 return 0; > 1933 } > 1934 > > --- > 0-DAY CI Kernel Test Service, Intel Corporation > https://lists.01.org/hyperkitty/list/kbuild-...@lists.01.org -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
