Hi Catalin,

I love your patch! Yet something to improve:

[auto build test ERROR on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/Catalin-Marinas/mm-dma-arm64-Reduce-ARCH_KMALLOC_MINALIGN-to-8/20221107-060303
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20221106220143.2129263-5-catalin.marinas%40arm.com
patch subject: [PATCH v3 04/13] mm/slab: Allow kmalloc() minimum alignment fallback to dma_get_cache_alignment()
config: hexagon-randconfig-r011-20221106
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 2bbafe04fe785a9469bea5a3737f8d7d3ce4aca2)
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://github.com/intel-lab-lkp/linux/commit/309bc52a1ed9665a1b9d32bcf094918ceb6af519
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Catalin-Marinas/mm-dma-arm64-Reduce-ARCH_KMALLOC_MINALIGN-to-8/20221107-060303
        git checkout 309bc52a1ed9665a1b9d32bcf094918ceb6af519
        # 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=hexagon SHELL=/bin/bash

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

All errors (new ones prefixed by >>):

   In file included from mm/slab_common.c:11:
   In file included from include/linux/interrupt.h:11:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:547:31: 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:560:61: 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/little_endian.h:37:51: note: expanded from macro '__le16_to_cpu'
   #define __le16_to_cpu(x) ((__force __u16)(__le16)(x))
                                                     ^
   In file included from mm/slab_common.c:11:
   In file included from include/linux/interrupt.h:11:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:573:61: 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/little_endian.h:35:51: note: expanded from macro '__le32_to_cpu'
   #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
                                                     ^
   In file included from mm/slab_common.c:11:
   In file included from include/linux/interrupt.h:11:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:584:33: 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:594:59: 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:604:59: 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);
                                                         ~~~~~~~~~~ ^
>> mm/slab_common.c:866:45: error: use of undeclared identifier 'io_tlb_default_mem'
               cache_align < ARCH_KMALLOC_MINALIGN || io_tlb_default_mem.nslabs)
                                                      ^
   6 warnings and 1 error generated.


vim +/io_tlb_default_mem +866 mm/slab_common.c

   856	
   857	static unsigned int __kmalloc_minalign(void)
   858	{
   859		int cache_align = dma_get_cache_alignment();
   860	
   861		/*
   862		 * If CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC is not enabled,
   863		 * ARCH_KMALLOC_MINALIGN matches ARCH_DMA_MINALIGN.
   864		 */
   865		if (!IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) ||
 > 866		    cache_align < ARCH_KMALLOC_MINALIGN || io_tlb_default_mem.nslabs)
   867			return ARCH_KMALLOC_MINALIGN;
   868	
   869		pr_info_once("No default DMA bounce buffer, increasing the kmalloc() minimum alignment to %d\n",
   870			     cache_align);
   871		return cache_align;
   872	}
   873	

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