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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 082F7C4363D for ; Wed, 7 Oct 2020 22:24:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B085B2083B for ; Wed, 7 Oct 2020 22:24:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=intel-com.20150623.gappssmtp.com header.i=@intel-com.20150623.gappssmtp.com header.b="QQSRcBFI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728846AbgJGWYL (ORCPT ); Wed, 7 Oct 2020 18:24:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49130 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728654AbgJGWYK (ORCPT ); Wed, 7 Oct 2020 18:24:10 -0400 Received: from mail-ed1-x543.google.com (mail-ed1-x543.google.com [IPv6:2a00:1450:4864:20::543]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D1F31C0613D2 for ; Wed, 7 Oct 2020 15:24:09 -0700 (PDT) Received: by mail-ed1-x543.google.com with SMTP id cq12so3854700edb.2 for ; Wed, 07 Oct 2020 15:24:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Zic23vwE4RxhL64QubFNAgrR6bPLwF/Sw808vPXOvcE=; b=QQSRcBFI6KAV++JS9/GFj7Fmw4j7a/iMiUg1ZTuLmVxWhkZMKv0QD8k1ukWq7eq/is aqhku7tesefyyeplMfP+uZ40G5Eu5h32eX3quWRsYX4t93t8hfPAksy+eKFnntLzh659 XKe6EgVkLvN8qFLGttYIbd5R75etFF329oIsGVg7tFamYwMf914oOqvj5Aj57gMZmmXn BdX+R3HH+c0ZbeHsryryJmXxzi8LbxHVyDfXa28xyWATs9steaqxyt3ORz7tJ5iS3p0B /C9lomlbRYU4nllCvXcMpiVBxaPdCxNSDAwt+Wnv7NkDlHC0AVoEJJmmbnIbcEEDMbkk VNvg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Zic23vwE4RxhL64QubFNAgrR6bPLwF/Sw808vPXOvcE=; b=HFcoiRUtYZmksIvpN5vNHxr6mVoOVqOy7/4DAnVSd19TnDdDRWg+mHIBXvh2jR/VFs PocUq5NNgr9hEgaP74rVPsxxXdjzyhvHoPKBZuuvCvCJ3gHwbyJY6xn2+UZfqz7n03OJ Yeciu00vju+aLVmZ0kkoUlEgWdhMJjrdYDiq6RkDX3e/aapboS+QdloU8CP89pq/oDZG vASZvj8LSeH9sXQBNgalHTAz61a0mAJlGDi6oRsIbYtBPUjwZQb74D1cMUPf6D9fNwg4 3Lvi0LVBH36RMoa9UrScG97NDrezyrnDO5v9PF6EOxcqt5P8kxtcs5iz6YCykww1b9f8 gAAQ== X-Gm-Message-State: AOAM530zrGW+/zIrpoInQIFbM5+NOZtjSxz8p0vsKastyRz1wL3X7D20 mty7Y31K+sitDmevO1P+HXVafX96bhYelit/8AizfQ== X-Google-Smtp-Source: ABdhPJyEbSoLmGrub89sZew46mtuYR5cC3wqZnDpHg2eEdBRv6ndP1ZtRmu/HFaFG/gOZx15NdgN0Q/4bhJSTz4VXAk= X-Received: by 2002:a50:d0d0:: with SMTP id g16mr5862132edf.18.1602109448239; Wed, 07 Oct 2020 15:24:08 -0700 (PDT) MIME-Version: 1.0 References: <20201007164426.1812530-1-daniel.vetter@ffwll.ch> <20201007164426.1812530-11-daniel.vetter@ffwll.ch> In-Reply-To: From: Dan Williams Date: Wed, 7 Oct 2020 15:23:57 -0700 Message-ID: Subject: Re: [PATCH 10/13] PCI: revoke mappings like devmem To: Daniel Vetter Cc: DRI Development , LKML , KVM list , Linux MM , Linux ARM , linux-samsung-soc , "Linux-media@vger.kernel.org" , linux-s390 , Daniel Vetter , Jason Gunthorpe , Kees Cook , Andrew Morton , John Hubbard , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Jan Kara , Bjorn Helgaas , Linux PCI Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 7, 2020 at 12:49 PM Daniel Vetter wrote: > > On Wed, Oct 7, 2020 at 9:33 PM Dan Williams wrote: > > > > On Wed, Oct 7, 2020 at 11:11 AM Daniel Vetter wrote: > > > > > > Since 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims > > > the region") /dev/kmem zaps ptes when the kernel requests exclusive > > > acccess to an iomem region. And with CONFIG_IO_STRICT_DEVMEM, this is > > > the default for all driver uses. > > > > > > Except there's two more ways to access pci bars: sysfs and proc mmap > > > support. Let's plug that hole. > > > > Ooh, yes, lets. > > > > > For revoke_devmem() to work we need to link our vma into the same > > > address_space, with consistent vma->vm_pgoff. ->pgoff is already > > > adjusted, because that's how (io_)remap_pfn_range works, but for the > > > mapping we need to adjust vma->vm_file->f_mapping. Usually that's done > > > at ->open time, but that's a bit tricky here with all the entry points > > > and arch code. So instead create a fake file and adjust vma->vm_file. > > > > I don't think you want to share the devmem inode for this, this should > > be based off the sysfs inode which I believe there is already only one > > instance per resource. In contrast /dev/mem can have multiple inodes > > because anyone can just mknod a new character device file, the same > > problem does not exist for sysfs. > > But then I need to find the right one, plus I also need to find the > right one for the procfs side. That gets messy, and I already have no > idea how to really test this. Shared address_space is the same trick > we're using in drm (where we have multiple things all pointing to the > same underlying resources, through different files), and it gets the > job done. So that's why I figured the shared address_space is the > cleaner solution since then unmap_mapping_range takes care of > iterating over all vma for us. I guess I could reimplement that logic > with our own locking and everything in revoke_devmem, but feels a bit > silly. But it would also solve the problem of having mutliple > different mknod of /dev/kmem with different address_space behind them. > Also because of how remap_pfn_range works, all these vma do use the > same pgoff already anyway. True, remap_pfn_range() makes sure that ->pgoff is an absolute physical address offset for all use cases. So you might be able to just point proc_bus_pci_open() at the shared devmem address space. For sysfs it's messier. I think you would need to somehow get the inode from kernfs_fop_open() to adjust its address space, but only if the bin_file will ultimately be used for PCI memory.