From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BF42DC433E0 for ; Wed, 3 Jun 2020 04:19:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9600520738 for ; Wed, 3 Jun 2020 04:19:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="huGDM1r+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725993AbgFCETB (ORCPT ); Wed, 3 Jun 2020 00:19:01 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:45079 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725927AbgFCETA (ORCPT ); Wed, 3 Jun 2020 00:19:00 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591157938; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9xmDIzzeJFmx6PBS/p46/Kx8Jkci56FFIVCj3VdkRT8=; b=huGDM1r++/S2JLPOCvVu7VzzVn2B2odZ3PR3YQQDF2DDUKcfD7XUGxnQTaEoeJ9WBYLG7A qyhza1BVfJ47CtcC3jmHBDKpQaHz1HZinkVSOrTjv/3qXBDSgFctp5MLWT9wx0IpnSAGqM AYyZS3M6uZJ7mBywu2ZziIqFQ1StN3Y= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-222-9cqdcdTcOAK175-ap0_q_A-1; Wed, 03 Jun 2020 00:18:54 -0400 X-MC-Unique: 9cqdcdTcOAK175-ap0_q_A-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 297FD461; Wed, 3 Jun 2020 04:18:53 +0000 (UTC) Received: from [10.72.12.214] (ovpn-12-214.pek2.redhat.com [10.72.12.214]) by smtp.corp.redhat.com (Postfix) with ESMTP id 46AF86C77F; Wed, 3 Jun 2020 04:18:45 +0000 (UTC) Subject: Re: [PATCH 4/6] vhost_vdpa: support doorbell mapping via mmap To: "Michael S. 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> From: Jason Wang Message-ID: <5db6b413-cb6c-a566-2f2d-ad580d8e165b@redhat.com> Date: Wed, 3 Jun 2020 12:18:44 +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: <20200602093025-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 10.5.11.15 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > > >>> >>>