Re: [PATCH 0/8] Convert the intel iommu driver to the dma-iommu api

From: Tom Murphy <murphyt7@tcd.ie>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Heiko Stuebner <heiko@sntech.de>,
	kvm@vger.kernel.org, David Airlie <airlied@linux.ie>,
	Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	dri-devel@lists.freedesktop.org,
	Matthias Brugger <matthias.bgg@gmail.com>,
	Julien Grall <julien.grall@arm.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	Will Deacon <will@kernel.org>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	linux-samsung-soc@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	linux-rockchip@lists.infradead.org,
	Andy Gross <agross@kernel.org>,
	Gerald Schaefer <gerald.schaefer@de.ibm.com>,
	linux-s390@vger.kernel.org, linux-arm-msm@vger.kernel.org,
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	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	linux-tegra@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
	virtualization@lists.linux-foundation.org,
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	Cornelia Huck <cohuck@redhat.com>,
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	Kukjin Kim <kgene@kernel.org>, Daniel Vetter <daniel@ffwll.ch>,
	David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH 0/8] Convert the intel iommu driver to the dma-iommu api
Date: Wed, 26 Aug 2020 14:23:26 -0400	[thread overview]
Message-ID: <CALQxJuttUa0=Z0dQrgxAE=+w-UeE5XPW3b3BBzujtJ3aw5J8LQ@mail.gmail.com> (raw)
In-Reply-To: <03caf286-09e8-a072-8d3a-b6bcca991516@arm.com>

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That would be great!

On Wed., Aug. 26, 2020, 2:14 p.m. Robin Murphy, <robin.murphy@arm.com>
wrote:

> Hi Tom,
>
> On 2019-12-21 15:03, Tom Murphy wrote:
> > This patchset converts the intel iommu driver to the dma-iommu api.
> >
> > While converting the driver I exposed a bug in the intel i915 driver
> which causes a huge amount of artifacts on the screen of my laptop. You can
> see a picture of it here:
> >
> https://github.com/pippy360/kernelPatches/blob/master/IMG_20191219_225922.jpg
> >
> > This issue is most likely in the i915 driver and is most likely caused
> by the driver not respecting the return value of the dma_map_ops::map_sg
> function. You can see the driver ignoring the return value here:
> >
> https://github.com/torvalds/linux/blob/7e0165b2f1a912a06e381e91f0f4e495f4ac3736/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c#L51
> >
> > Previously this didn’t cause issues because the intel map_sg always
> returned the same number of elements as the input scatter gather list but
> with the change to this dma-iommu api this is no longer the case. I wasn’t
> able to track the bug down to a specific line of code unfortunately.
> >
> > Could someone from the intel team look at this?
> >
> >
> > I have been testing on a lenovo x1 carbon 5th generation. Let me know if
> there’s any more information you need.
> >
> > To allow my patch set to be tested I have added a patch (patch 8/8) in
> this series to disable combining sg segments in the dma-iommu api which
> fixes the bug but it doesn't fix the actual problem.
> >
> > As part of this patch series I copied the intel bounce buffer code to
> the dma-iommu path. The addition of the bounce buffer code took me by
> surprise. I did most of my development on this patch series before the
> bounce buffer code was added and my reimplementation in the dma-iommu path
> is very rushed and not properly tested but I’m running out of time to work
> on this patch set.
> >
> > On top of that I also didn’t port over the intel tracing code from this
> commit:
> >
> https://github.com/torvalds/linux/commit/3b53034c268d550d9e8522e613a14ab53b8840d8#diff-6b3e7c4993f05e76331e463ab1fc87e1
> > So all the work in that commit is now wasted. The code will need to be
> removed and reimplemented in the dma-iommu path. I would like to take the
> time to do this but I really don’t have the time at the moment and I want
> to get these changes out before the iommu code changes any more.
>
> Further to what we just discussed at LPC, I've realised that tracepoints
> are actually something I could do with *right now* for debugging my Arm
> DMA ops series, so if I'm going to hack something up anyway I may as
> well take responsibility for polishing it into a proper patch as well :)
>
> Robin.
>
> >
> > Tom Murphy (8):
> >    iommu/vt-d: clean up 32bit si_domain assignment
> >    iommu/vt-d: Use default dma_direct_* mapping functions for direct
> >      mapped devices
> >    iommu/vt-d: Remove IOVA handling code from non-dma_ops path
> >    iommu: Handle freelists when using deferred flushing in iommu drivers
> >    iommu: Add iommu_dma_free_cpu_cached_iovas function
> >    iommu: allow the dma-iommu api to use bounce buffers
> >    iommu/vt-d: Convert intel iommu driver to the iommu ops
> >    DO NOT MERGE: iommu: disable list appending in dma-iommu
> >
> >   drivers/iommu/Kconfig           |   1 +
> >   drivers/iommu/amd_iommu.c       |  14 +-
> >   drivers/iommu/arm-smmu-v3.c     |   3 +-
> >   drivers/iommu/arm-smmu.c        |   3 +-
> >   drivers/iommu/dma-iommu.c       | 183 +++++--
> >   drivers/iommu/exynos-iommu.c    |   3 +-
> >   drivers/iommu/intel-iommu.c     | 936 ++++----------------------------
> >   drivers/iommu/iommu.c           |  39 +-
> >   drivers/iommu/ipmmu-vmsa.c      |   3 +-
> >   drivers/iommu/msm_iommu.c       |   3 +-
> >   drivers/iommu/mtk_iommu.c       |   3 +-
> >   drivers/iommu/mtk_iommu_v1.c    |   3 +-
> >   drivers/iommu/omap-iommu.c      |   3 +-
> >   drivers/iommu/qcom_iommu.c      |   3 +-
> >   drivers/iommu/rockchip-iommu.c  |   3 +-
> >   drivers/iommu/s390-iommu.c      |   3 +-
> >   drivers/iommu/tegra-gart.c      |   3 +-
> >   drivers/iommu/tegra-smmu.c      |   3 +-
> >   drivers/iommu/virtio-iommu.c    |   3 +-
> >   drivers/vfio/vfio_iommu_type1.c |   2 +-
> >   include/linux/dma-iommu.h       |   3 +
> >   include/linux/intel-iommu.h     |   1 -
> >   include/linux/iommu.h           |  32 +-
> >   23 files changed, 345 insertions(+), 908 deletions(-)
> >
>

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