Hi Eric,

I love your patch! Perhaps something to improve:

[auto build test WARNING on v5.10-rc4]
[also build test WARNING on next-20201116]
[cannot apply to vfio/next]
[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/Eric-Auger/SMMUv3-Nested-Stage-Setup-VFIO-part/20201116-190742
base:    09162bc32c880a791c6c0668ce0745cf7958f576
config: x86_64-allyesconfig (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/747ef402696e1192684908ca99f06f3d68466c04
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Eric-Auger/SMMUv3-Nested-Stage-Setup-VFIO-part/20201116-190742
        git checkout 747ef402696e1192684908ca99f06f3d68466c04
        # save the attached .config to linux build tree
        make W=1 ARCH=x86_64 

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 include/linux/vfio.h:16,
                    from drivers/vfio/pci/vfio_pci.c:26:
   include/uapi/linux/vfio.h:1231:34: error: field 'config' has incomplete type
    1231 |  struct iommu_pasid_table_config config; /* used on SET */
         |                                  ^~~~~~
>> drivers/vfio/pci/vfio_pci.c:339:5: warning: no previous prototype for 'vfio_pci_iommu_dev_fault_handler' [-Wmissing-prototypes]
     339 | int vfio_pci_iommu_dev_fault_handler(struct iommu_fault *fault, void *data)
         |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

vim +/vfio_pci_iommu_dev_fault_handler +339 drivers/vfio/pci/vfio_pci.c

   338	
 > 339	int vfio_pci_iommu_dev_fault_handler(struct iommu_fault *fault, void *data)
   340	{
   341		struct vfio_pci_device *vdev = (struct vfio_pci_device *)data;
   342		struct vfio_region_dma_fault *reg =
   343			(struct vfio_region_dma_fault *)vdev->fault_pages;
   344		struct iommu_fault *new;
   345		u32 head, tail, size;
   346		int ret = -EINVAL;
   347	
   348	
   349		if (WARN_ON(!reg))
   350			return ret;
   351	
   352		mutex_lock(&vdev->fault_queue_lock);
   353	
   354		head = reg->head;
   355		tail = reg->tail;
   356		size = reg->nb_entries;
   357	
   358		new = (struct iommu_fault *)(vdev->fault_pages + reg->offset +
   359					     head * reg->entry_size);
   360	
   361		if (CIRC_SPACE(head, tail, size) < 1) {
   362			ret = -ENOSPC;
   363			goto unlock;
   364		}
   365	
   366		*new = *fault;
   367		reg->head = (head + 1) % size;
   368		ret = 0;
   369	unlock:
   370		mutex_unlock(&vdev->fault_queue_lock);
   371		return ret;
   372	}
   373	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org