From: Will Deacon <will.deacon@arm.com>
To: Mitchel Humpherys <mitchelh@codeaurora.org>
Cc: iommu@lists.linux-foundation.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Robin Murphy <robin.murphy@arm.com>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Jordan Crouse <jcrouse@codeaurora.org>,
Jeremy Gebben <jgebben@codeaurora.org>,
Patrick Daly <pdaly@codeaurora.org>,
Pratik Patel <pratikp@codeaurora.org>,
Thomas Zeng <tzeng@codeaurora.org>
Subject: Re: [PATCH v3 0/6] Add support for privileged mappings
Date: Mon, 25 Jul 2016 10:50:13 +0100 [thread overview]
Message-ID: <20160725095012.GC15864@arm.com> (raw)
In-Reply-To: <vnkweg6l9zla.fsf@codeaurora.org>
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 <will.deacon@arm.com> 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 <robin.murphy@arm.com>
> >> 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 <will.deacon@arm.com>
> >
> > 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.
Will
next prev parent reply other threads:[~2016-07-25 9:50 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-19 20:36 [PATCH v3 0/6] Add support for privileged mappings Mitchel Humpherys
2016-07-19 20:36 ` [PATCH v3 1/6] iommu: add IOMMU_PRIV attribute Mitchel Humpherys
[not found] ` <20160719203655.16629-1-mitchelh-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2016-07-19 20:36 ` [PATCH v3 2/6] iommu/io-pgtable-arm: add support for the IOMMU_PRIV flag Mitchel Humpherys
2016-07-19 20:36 ` [PATCH v3 3/6] common: DMA-mapping: add DMA_ATTR_PRIVILEGED attribute Mitchel Humpherys
2016-07-19 20:36 ` [PATCH v3 4/6] arm64/dma-mapping: Implement DMA_ATTR_PRIVILEGED Mitchel Humpherys
2016-07-19 20:36 ` [PATCH v3 5/6] dmaengine: pl330: Make sure microcode is privileged Mitchel Humpherys
2016-07-19 20:36 ` [PATCH v3 6/6] Revert "iommu/arm-smmu: Treat all device transactions as unprivileged" Mitchel Humpherys
2016-07-22 16:51 ` [PATCH v3 0/6] Add support for privileged mappings Will Deacon
2016-07-22 20:39 ` Mitchel Humpherys
2016-07-25 9:50 ` Will Deacon [this message]
2016-07-25 19:01 ` Mitchel Humpherys
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