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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_RED autolearn=unavailable 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 3B960C433E0 for ; Tue, 19 Jan 2021 22:45:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0ABC422D08 for ; Tue, 19 Jan 2021 22:45:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730452AbhASWow (ORCPT ); Tue, 19 Jan 2021 17:44:52 -0500 Received: from mail.kernel.org ([198.145.29.99]:33384 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405480AbhASOcr (ORCPT ); Tue, 19 Jan 2021 09:32:47 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2014F206E9; Tue, 19 Jan 2021 14:32:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1611066726; bh=Tduvv18LK/LCkLs3ZnFGc8LwDL80UuULmc4HIuM8pAY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=prM3R5m3uo3uXxwz5GeHrVafgNEbazb911/CI5WpXB7mO0+x4TdgpD/xfl7vPnlJZ RQsVqKJuk3PN4R4txzMSyCZaE72+c4UfnjcSxVefqnxyckuXd2lD6+sVDOm9sB3/vH hju2ZT4LQV1lPp7LQu8FKl+QWHFfDJWRhHidhWT8= Date: Tue, 19 Jan 2021 15:32:04 +0100 From: Greg Kroah-Hartman To: Daniel Vetter Cc: DRI Development , LKML , Stephen Rothwell , KVM list , Linux MM , Linux ARM , linux-samsung-soc , "open list:DMA BUFFER SHARING FRAMEWORK" , Bjorn Helgaas , Dan Williams , Daniel Vetter , Jason Gunthorpe , Kees Cook , Andrew Morton , John Hubbard , =?iso-8859-1?B?Suly9G1l?= Glisse , Jan Kara , Linux PCI Subject: Re: [PATCH v7 12/17] PCI: Revoke mappings like devmem Message-ID: References: <20201127164131.2244124-1-daniel.vetter@ffwll.ch> <20201127164131.2244124-13-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 19, 2021 at 09:17:55AM +0100, Daniel Vetter wrote: > On Fri, Nov 27, 2020 at 5:42 PM 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. > > > > 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. The cleanest way is > > to adjust this at at ->open time: > > > > - for sysfs this is easy, now that binary attributes support this. We > > just set bin_attr->mapping when mmap is supported > > - for procfs it's a bit more tricky, since procfs pci access has only > > one file per device, and access to a specific resources first needs > > to be set up with some ioctl calls. But mmap is only supported for > > the same resources as sysfs exposes with mmap support, and otherwise > > rejected, so we can set the mapping unconditionally at open time > > without harm. > > > > A special consideration is for arch_can_pci_mmap_io() - we need to > > make sure that the ->f_mapping doesn't alias between ioport and iomem > > space. There's only 2 ways in-tree to support mmap of ioports: generic > > pci mmap (ARCH_GENERIC_PCI_MMAP_RESOURCE), and sparc as the single > > architecture hand-rolling. Both approach support ioport mmap through a > > special pfn range and not through magic pte attributes. Aliasing is > > therefore not a problem. > > > > The only difference in access checks left is that sysfs PCI mmap does > > not check for CAP_RAWIO. I'm not really sure whether that should be > > added or not. > > > > Acked-by: Bjorn Helgaas > > Reviewed-by: Dan Williams > > Signed-off-by: Daniel Vetter > > Cc: Jason Gunthorpe > > Cc: Kees Cook > > Cc: Dan Williams > > Cc: Andrew Morton > > Cc: John Hubbard > > Cc: Jérôme Glisse > > Cc: Jan Kara > > Cc: Dan Williams > > Cc: Greg Kroah-Hartman > > Cc: linux-mm@kvack.org > > Cc: linux-arm-kernel@lists.infradead.org > > Cc: linux-samsung-soc@vger.kernel.org > > Cc: linux-media@vger.kernel.org > > Cc: Bjorn Helgaas > > Cc: linux-pci@vger.kernel.org > > Signed-off-by: Daniel Vetter > > -- > > v2: > > - Totally new approach: Adjust filp->f_mapping at open time. Note that > > this now works on all architectures, not just those support > > ARCH_GENERIC_PCI_MMAP_RESOURCE > > --- > > drivers/pci/pci-sysfs.c | 4 ++++ > > drivers/pci/proc.c | 1 + > > 2 files changed, 5 insertions(+) > > > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c > > index d15c881e2e7e..3f1c31bc0b7c 100644 > > --- a/drivers/pci/pci-sysfs.c > > +++ b/drivers/pci/pci-sysfs.c > > @@ -929,6 +929,7 @@ void pci_create_legacy_files(struct pci_bus *b) > > b->legacy_io->read = pci_read_legacy_io; > > b->legacy_io->write = pci_write_legacy_io; > > b->legacy_io->mmap = pci_mmap_legacy_io; > > + b->legacy_io->mapping = iomem_get_mapping(); > > pci_adjust_legacy_attr(b, pci_mmap_io); > > error = device_create_bin_file(&b->dev, b->legacy_io); > > if (error) > > @@ -941,6 +942,7 @@ void pci_create_legacy_files(struct pci_bus *b) > > b->legacy_mem->size = 1024*1024; > > b->legacy_mem->attr.mode = 0600; > > b->legacy_mem->mmap = pci_mmap_legacy_mem; > > + b->legacy_io->mapping = iomem_get_mapping(); > > Unlike the normal pci stuff below, the legacy files here go boom > because they're set up much earlier in the boot sequence. This only > affects HAVE_PCI_LEGACY architectures, which aren't that many. So what > should we do here now: > - drop the devmem revoke for these > - rework the init sequence somehow to set up these files a lot later > - redo the sysfs patch so that it doesn't take an address_space > pointer, but instead a callback to get at that (since at open time > everything is set up). Imo rather ugly > - ditch this part of the series (since there's not really any takers > for the latter parts it might just not make sense to push for this) > - something else? > > Bjorn, Greg, thoughts? What sysfs patch are you referring to here? thanks, greg k-h