Messages in this thread | | | Subject | Re: [PATCH 4/6] vhost_vdpa: support doorbell mapping via mmap | From | Jason Wang <> | Date | Wed, 3 Jun 2020 14:37:51 +0800 |
| |
On 2020/6/3 下午2:34, Michael S. Tsirkin wrote: > On Wed, Jun 03, 2020 at 12:18:44PM +0800, Jason Wang wrote: >> On 2020/6/2 下午9:31, Michael S. Tsirkin wrote: >>> On Tue, Jun 02, 2020 at 02:49:38PM +0800, Jason Wang wrote: >>>> 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 >>> Well >>> >>> int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr, >>> unsigned long pfn, unsigned long size, pgprot_t prot) >>> { >>> if (addr != (pfn << PAGE_SHIFT)) >>> return -EINVAL; >>> >>> vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP; >>> return 0; >>> } >>> EXPORT_SYMBOL(remap_pfn_range); >>> >>> >>> So things aren't going to work if you have a fixed PFN >>> which is the case of the hardware device. >> Looking at the implementation of some drivers e.g mtd_char. If I read the >> code correctly, we can do this by providing get_unmapped_area method and use >> physical address directly. >> >> But start form CONFIG_MMU should be fine. Do you prefer making vhost_vdpa >> depends on CONFIG_MMU or just fail mmap when CONFIG_MMU is not configured? >> >> Thanks > I'd just not specify the mmap callback at all.
Ok, will do.
Thanks
>
| |