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SubjectRe: [PATCH 4/6] vhost_vdpa: support doorbell mapping via mmap
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On 2020/6/2 下午12:56, Michael S. Tsirkin wrote:
> On Tue, Jun 02, 2020 at 03:22:49AM +0800, kbuild test robot wrote:
>> Hi Jason,
>>
>> I love your patch! Yet something to improve:
>>
>> [auto build test ERROR on vhost/linux-next]
>> [also build test ERROR on linus/master v5.7 next-20200529]
>> [if your patch is applied to the wrong git tree, please drop us a note to help
>> improve the system. BTW, we also suggest to use '--base' option to specify the
>> base tree in git format-patch, please seehttps://stackoverflow.com/a/37406982]
>>
>> url:https://github.com/0day-ci/linux/commits/Jason-Wang/vDPA-doorbell-mapping/20200531-070834
>> base:https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git linux-next
>> config: m68k-randconfig-r011-20200601 (attached as .config)
>> compiler: m68k-linux-gcc (GCC) 9.3.0
>> reproduce (this is a W=1 build):
>> wgethttps://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>> chmod +x ~/bin/make.cross
>> # save the attached .config to linux build tree
>> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=m68k
>>
>> If you fix the issue, kindly add following tag as appropriate
>> Reported-by: kbuild test robot<lkp@intel.com>
>>
>> All errors (new ones prefixed by >>, old ones prefixed by <<):
>>
>> drivers/vhost/vdpa.c: In function 'vhost_vdpa_fault':
>>>> drivers/vhost/vdpa.c:754:22: error: implicit declaration of function 'pgprot_noncached' [-Werror=implicit-function-declaration]
>> 754 | vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
>> | ^~~~~~~~~~~~~~~~
>>>> drivers/vhost/vdpa.c:754:22: error: incompatible types when assigning to type 'pgprot_t' {aka 'struct <anonymous>'} from type 'int'
>> cc1: some warnings being treated as errors
>>
>> vim +/pgprot_noncached +754 drivers/vhost/vdpa.c
>>
>> 742
>> 743 static vm_fault_t vhost_vdpa_fault(struct vm_fault *vmf)
>> 744 {
>> 745 struct vhost_vdpa *v = vmf->vma->vm_file->private_data;
>> 746 struct vdpa_device *vdpa = v->vdpa;
>> 747 const struct vdpa_config_ops *ops = vdpa->config;
>> 748 struct vdpa_notification_area notify;
>> 749 struct vm_area_struct *vma = vmf->vma;
>> 750 u16 index = vma->vm_pgoff;
>> 751
>> 752 notify = ops->get_vq_notification(vdpa, index);
>> 753
>> > 754 vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
>> 755 if (remap_pfn_range(vma, vmf->address & PAGE_MASK,
>> 756 notify.addr >> PAGE_SHIFT, PAGE_SIZE,
>> 757 vma->vm_page_prot))
>> 758 return VM_FAULT_SIGBUS;
>> 759
>> 760 return VM_FAULT_NOPAGE;
>> 761 }
>> 762
> Yes well, all this remapping clearly has no chance to work
> on systems without CONFIG_MMU.


It looks to me mmap can work according to Documentation/nommu-mmap.txt.
But I'm not sure it's worth to bother.

Thanks


>
>
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