From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mitchel Humpherys Subject: Re: [PATCH v3 0/6] Add support for privileged mappings Date: Mon, 25 Jul 2016 12:01:05 -0700 Message-ID: References: <20160719203655.16629-1-mitchelh@codeaurora.org> <20160722165107.GH16837@arm.com> <20160725095012.GC15864@arm.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <20160725095012.GC15864@arm.com> (Will Deacon's message of "Mon, 25 Jul 2016 10:50:13 +0100") Sender: linux-kernel-owner@vger.kernel.org To: Will Deacon Cc: iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Robin Murphy , Marek Szyprowski , Jordan Crouse , Jeremy Gebben , Patrick Daly , Pratik Patel , Thomas Zeng List-Id: iommu@lists.linux-foundation.org On Mon, Jul 25 2016 at 10:50:13 AM, Will Deacon wrote: > On Fri, Jul 22, 2016 at 01:39:45PM -0700, Mitchel Humpherys wrote: >> On Fri, Jul 22 2016 at 05:51:07 PM, Will Deacon wrote: >> > On Tue, Jul 19, 2016 at 01:36:49PM -0700, Mitchel Humpherys wrote: >> >> The following patch to the ARM SMMU driver: >> >> >> >> commit d346180e70b91b3d5a1ae7e5603e65593d4622bc >> >> Author: Robin Murphy >> >> Date: Tue Jan 26 18:06:34 2016 +0000 >> >> >> >> iommu/arm-smmu: Treat all device transactions as unprivileged >> >> >> >> started forcing all SMMU transactions to come through as "unprivileged". >> >> The rationale given was that: >> >> >> >> (1) There is no way in the IOMMU API to even request privileged mappings. >> >> >> >> (2) It's difficult to implement a DMA mapper that correctly models the >> >> ARM VMSAv8 behavior of unprivileged-writeable => >> >> privileged-execute-never. >> >> >> >> This series rectifies (1) by introducing an IOMMU API for privileged >> >> mappings and implements it in io-pgtable-arm. >> >> >> >> This series rectifies (2) by introducing a new dma attribute >> >> (DMA_ATTR_PRIVILEGED) for users of the DMA API that need privileged >> >> mappings which are inaccessible to lesser-privileged execution levels, and >> >> implements it in the arm64 IOMMU DMA mapper. The one known user (pl330.c) >> >> is converted over to the new attribute. >> >> >> >> Jordan and Jeremy can provide more info on the use case if needed, but the >> >> high level is that it's a security feature to prevent attacks such as [1]. >> > >> > This all looks good to me: >> > >> > Acked-by: Will Deacon >> > >> > It looks pretty fiddly to merge, however. How are you planning to get >> > this upstream? >> >> Fiddly in what way? Do you mean in relation to "dma-mapping: Use >> unsigned long for dma_attrs" [1]? I admit I wasn't aware of that >> activity until Robin mentioned it. It looks like it's merged on >> next/master, shall I rebase/rework on that and resend? > > Fiddly in that it touches multiple subsystems. I guess routing it via > the iommu tree (Joerg) might be the best bet. Sounds good. I'm going to rebase on linux-next as well anyways to get the new dma attrs format and resend. -Mitch -- Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project From mboxrd@z Thu Jan 1 00:00:00 1970 From: mitchelh@codeaurora.org (Mitchel Humpherys) Date: Mon, 25 Jul 2016 12:01:05 -0700 Subject: [PATCH v3 0/6] Add support for privileged mappings In-Reply-To: <20160725095012.GC15864@arm.com> (Will Deacon's message of "Mon, 25 Jul 2016 10:50:13 +0100") References: <20160719203655.16629-1-mitchelh@codeaurora.org> <20160722165107.GH16837@arm.com> <20160725095012.GC15864@arm.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Jul 25 2016 at 10:50:13 AM, Will Deacon wrote: > On Fri, Jul 22, 2016 at 01:39:45PM -0700, Mitchel Humpherys wrote: >> On Fri, Jul 22 2016 at 05:51:07 PM, Will Deacon wrote: >> > On Tue, Jul 19, 2016 at 01:36:49PM -0700, Mitchel Humpherys wrote: >> >> The following patch to the ARM SMMU driver: >> >> >> >> commit d346180e70b91b3d5a1ae7e5603e65593d4622bc >> >> Author: Robin Murphy >> >> Date: Tue Jan 26 18:06:34 2016 +0000 >> >> >> >> iommu/arm-smmu: Treat all device transactions as unprivileged >> >> >> >> started forcing all SMMU transactions to come through as "unprivileged". >> >> The rationale given was that: >> >> >> >> (1) There is no way in the IOMMU API to even request privileged mappings. >> >> >> >> (2) It's difficult to implement a DMA mapper that correctly models the >> >> ARM VMSAv8 behavior of unprivileged-writeable => >> >> privileged-execute-never. >> >> >> >> This series rectifies (1) by introducing an IOMMU API for privileged >> >> mappings and implements it in io-pgtable-arm. >> >> >> >> This series rectifies (2) by introducing a new dma attribute >> >> (DMA_ATTR_PRIVILEGED) for users of the DMA API that need privileged >> >> mappings which are inaccessible to lesser-privileged execution levels, and >> >> implements it in the arm64 IOMMU DMA mapper. The one known user (pl330.c) >> >> is converted over to the new attribute. >> >> >> >> Jordan and Jeremy can provide more info on the use case if needed, but the >> >> high level is that it's a security feature to prevent attacks such as [1]. >> > >> > This all looks good to me: >> > >> > Acked-by: Will Deacon >> > >> > It looks pretty fiddly to merge, however. How are you planning to get >> > this upstream? >> >> Fiddly in what way? Do you mean in relation to "dma-mapping: Use >> unsigned long for dma_attrs" [1]? I admit I wasn't aware of that >> activity until Robin mentioned it. It looks like it's merged on >> next/master, shall I rebase/rework on that and resend? > > Fiddly in that it touches multiple subsystems. I guess routing it via > the iommu tree (Joerg) might be the best bet. Sounds good. I'm going to rebase on linux-next as well anyways to get the new dma attrs format and resend. -Mitch -- Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project