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 Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BB1B8C433F5 for ; Tue, 26 Apr 2022 11:15:51 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 5122B405BB; Tue, 26 Apr 2022 11:15:51 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 79-eXI8zxOPW; Tue, 26 Apr 2022 11:15:50 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp2.osuosl.org (Postfix) with ESMTPS id 13C4B40B34; Tue, 26 Apr 2022 11:15:50 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id E33F5C0039; Tue, 26 Apr 2022 11:15:49 +0000 (UTC) Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id 1C0FAC0039 for ; Tue, 26 Apr 2022 11:15:49 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id D3E6140B3A for ; Tue, 26 Apr 2022 11:15:48 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id LxC1K8l98gLS for ; Tue, 26 Apr 2022 11:15:47 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp2.osuosl.org (Postfix) with ESMTP id AC1D840B20 for ; Tue, 26 Apr 2022 11:15:47 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BB8B023A; Tue, 26 Apr 2022 04:15:46 -0700 (PDT) Received: from [10.57.80.98] (unknown [10.57.80.98]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 99EA53F5A1; Tue, 26 Apr 2022 04:15:43 -0700 (PDT) Message-ID: <030f48f4-44d7-c04c-a194-5f4999873ebe@arm.com> Date: Tue, 26 Apr 2022 12:15:37 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [PATCH v6 1/2] PCI/ACPI: Support Microsoft's "DmaProperty" Content-Language: en-GB To: Rajat Jain , "Rafael J. Wysocki" , Len Brown , linux-pci@vger.kernel.org, Mika Westerberg , Greg Kroah-Hartman , Bjorn Helgaas , Bjorn Helgaas , ACPI Devel Maling List , Linux Kernel Mailing List , Rajat Jain , Dmitry Torokhov , Jesse Barnes , Jean-Philippe Brucker , Pavel Machek , Oliver O'Halloran , Joerg Roedel , Will Deacon , David Woodhouse , Lu Baolu , iommu@lists.linux-foundation.org References: <20220426000640.3581446-1-rajatja@google.com> From: Robin Murphy In-Reply-To: <20220426000640.3581446-1-rajatja@google.com> Cc: "Rafael J . Wysocki" X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 2022-04-26 01:06, Rajat Jain via iommu wrote: > The "DmaProperty" is supported and currently documented and used by > Microsoft [link 1 below], to flag internal PCIe root ports that need > DMA protection [link 2 below]. We have discussed with them and reached > a common understanding that they shall change their MSDN documentation > to say that the same property can be used to protect any PCI device, > and not just internal PCIe root ports (since there is no point > introducing yet another property for arbitrary PCI devices). This helps > with security from internal devices that offer an attack surface for > DMA attacks (e.g. internal network devices). > > Support DmaProperty to mark DMA from a PCI device as untrusted. > > Link: [1] https://docs.microsoft.com/en-us/windows-hardware/drivers/pci/dsd-for-pcie-root-ports#identifying-internal-pcie-ports-accessible-to-users-and-requiring-dma-protection > Link: [2] https://docs.microsoft.com/en-us/windows/security/information-protection/kernel-dma-protection-for-thunderbolt > Signed-off-by: Rajat Jain > Reviewed-by: Mika Westerberg > Acked-by: Rafael J. Wysocki > --- > v6: * Take care of Bjorn's comments: > - Update the commit log > - Rename to pci_dev_has_dma_property() > - Use acpi_dev_get_property() > v5: * Reorder the patches in the series > v4: * Add the GUID. > * Update the comment and commitlog. > v3: * Use Microsoft's documented property "DmaProperty" > * Resctrict to ACPI only > > drivers/acpi/property.c | 3 +++ > drivers/pci/pci-acpi.c | 21 +++++++++++++++++++++ > 2 files changed, 24 insertions(+) > > diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c > index 12bbfe833609..bafe35c301ac 100644 > --- a/drivers/acpi/property.c > +++ b/drivers/acpi/property.c > @@ -48,6 +48,9 @@ static const guid_t prp_guids[] = { > /* Storage device needs D3 GUID: 5025030f-842f-4ab4-a561-99a5189762d0 */ > GUID_INIT(0x5025030f, 0x842f, 0x4ab4, > 0xa5, 0x61, 0x99, 0xa5, 0x18, 0x97, 0x62, 0xd0), > + /* DmaProperty for PCI devices GUID: 70d24161-6dd5-4c9e-8070-705531292865 */ > + GUID_INIT(0x70d24161, 0x6dd5, 0x4c9e, > + 0x80, 0x70, 0x70, 0x55, 0x31, 0x29, 0x28, 0x65), > }; > > /* ACPI _DSD data subnodes GUID: dbb8e3e6-5886-4ba6-8795-1319f52a966b */ > diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c > index 3ae435beaf0a..d7c6ba48486f 100644 > --- a/drivers/pci/pci-acpi.c > +++ b/drivers/pci/pci-acpi.c > @@ -1369,12 +1369,33 @@ static void pci_acpi_set_external_facing(struct pci_dev *dev) > dev->external_facing = 1; > } > > +static int pci_dev_has_dma_property(struct pci_dev *dev) > +{ > + struct acpi_device *adev; > + const union acpi_object *obj; > + > + adev = ACPI_COMPANION(&dev->dev); > + if (!adev) > + return 0; > + > + /* > + * Property also used by Microsoft Windows for same purpose, > + * (to implement DMA protection from a device, using the IOMMU). Nit: there is no context for "same purpose" here, so this comment is more confusing than helpful. Might I suggest a rewording like: /* * Property used by Microsoft Windows to enforce IOMMU DMA * protection for any device that the system might not fully * trust; we'll honour it the same way. */ ? Personally I think it would have been more logical to handle this in pci_set_dma_untrusted(), but I see some of those implementation aspects have already been discussed, and Bjorn's preference definitely wins over mine here :) Thanks, Robin. > + */ > + if (!acpi_dev_get_property(adev, "DmaProperty", ACPI_TYPE_INTEGER, > + &obj) && obj->integer.value == 1) > + return 1; > + > + return 0; > +} > + > void pci_acpi_setup(struct device *dev, struct acpi_device *adev) > { > struct pci_dev *pci_dev = to_pci_dev(dev); > > pci_acpi_optimize_delay(pci_dev, adev->handle); > pci_acpi_set_external_facing(pci_dev); > + pci_dev->untrusted |= pci_dev_has_dma_property(pci_dev); > pci_acpi_add_edr_notifier(pci_dev); > > pci_acpi_add_pm_notifier(adev, pci_dev); _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu