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Tsirkin" Cc: kbuild test robot , kbuild-all@lists.01.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, rob.miller@broadcom.com, lingshan.zhu@intel.com, eperezma@redhat.com, lulu@redhat.com References: <20200529080303.15449-5-jasowang@redhat.com> <202006020308.kLXTHt4n%lkp@intel.com> <20200602005007-mutt-send-email-mst@kernel.org> <20200602093025-mutt-send-email-mst@kernel.org> <5db6b413-cb6c-a566-2f2d-ad580d8e165b@redhat.com> <20200603023429-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: <3c4ed3de-00e9-2e3d-854e-4bd47063820b@redhat.com> Date: Wed, 3 Jun 2020 14:37:51 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200603023429-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 >>>>>> >>>>>> 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 '} 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 >