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Date: Sat, 10 Feb 2024 19:27:46 +0800
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Cc: baolu.lu@linux.intel.com, Vineet Gupta <vgupta@kernel.org>,
 Russell King <linux@armlinux.org.uk>,
 Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>,
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 linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
 linux-acpi@vger.kernel.org, iommu@lists.linux.dev, devicetree@vger.kernel.org
Subject: Re: [PATCH v3 6/7] iommu/dma: Centralise iommu_setup_dma_ops()
To: Robin Murphy <robin.murphy@arm.com>
References: <cover.1707493264.git.robin.murphy@arm.com>
 <202fcca3269201bc9c4a8198253f195433d0c4ff.1707493264.git.robin.murphy@arm.com>
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From: Baolu Lu <baolu.lu@linux.intel.com>
In-Reply-To: <202fcca3269201bc9c4a8198253f195433d0c4ff.1707493264.git.robin.murphy@arm.com>
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On 2024/2/10 0:50, Robin Murphy wrote:
> It's somewhat hard to see, but arm64's arch_setup_dma_ops() should only
> ever call iommu_setup_dma_ops() after a successful iommu_probe_device(),
> which means there should be no harm in achieving the same order of
> operations by running it off the back of iommu_probe_device() itself.
> This then puts it in line with the x86 and s390 .probe_finalize bodges,
> letting us pull it all into the main flow properly. As a bonus this lets
> us fold in and de-scope the PCI workaround setup as well.
> 
> At this point we can also then pull the call up inside the group mutex,
> and avoid having to think about whether iommu_group_store_type() could
> theoretically race and free the domain if iommu_setup_dma_ops() ran just
> *before*  iommu_device_use_default_domain() claims it... Furthermore we
> replace one .probe_finalize call completely, since the only remaining
> implementations are now one which only needs to run once for the initial
> boot-time probe, and two which themselves render that path unreachable.
> 
> This leaves us a big step closer to realistically being able to unpick
> the variety of different things that iommu_setup_dma_ops() has been
> muddling together, and further streamline iommu-dma into core API flows
> in future.
> 
> Signed-off-by: Robin Murphy<robin.murphy@arm.com>
> ---
> v2: Shuffle around to make sure the iommu_group_do_probe_finalize() case
>      is covered as well, with bonus side-effects as above.
> v3:*Really*  do that, remembering the other two probe_finalize sites too.
> ---
>   arch/arm64/mm/dma-mapping.c  |  2 --
>   drivers/iommu/amd/iommu.c    |  8 --------
>   drivers/iommu/dma-iommu.c    | 18 ++++++------------
>   drivers/iommu/dma-iommu.h    | 14 ++++++--------
>   drivers/iommu/intel/iommu.c  |  7 -------
>   drivers/iommu/iommu.c        | 20 +++++++-------------
>   drivers/iommu/s390-iommu.c   |  6 ------
>   drivers/iommu/virtio-iommu.c | 10 ----------
>   include/linux/iommu.h        |  7 -------
>   9 files changed, 19 insertions(+), 73 deletions(-)

For changes in Intel IOMMU driver,

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>

Best regards,
baolu