linux-kernel - Re: [PATCH v3 6/7] iommu/dma: Centralise iommu_setup_dma

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Date: Sat, 10 Feb 2024 19:27:46 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Robin Murphy <robin.murphy@....com>
Cc: baolu.lu@...ux.intel.com, Vineet Gupta <vgupta@...nel.org>,
 Russell King <linux@...linux.org.uk>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>,
 Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>, Hanjun Guo
 <guohanjun@...wei.com>, Sudeep Holla <sudeep.holla@....com>,
 "K. Y. Srinivasan" <kys@...rosoft.com>,
 Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>,
 Dexuan Cui <decui@...rosoft.com>,
 Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
 David Woodhouse <dwmw2@...radead.org>,
 Niklas Schnelle <schnelle@...ux.ibm.com>,
 Matthew Rosato <mjrosato@...ux.ibm.com>,
 Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
 Jean-Philippe Brucker <jean-philippe@...aro.org>,
 Rob Herring <robh+dt@...nel.org>, Frank Rowand <frowand.list@...il.com>,
 Marek Szyprowski <m.szyprowski@...sung.com>, Jason Gunthorpe <jgg@...pe.ca>,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-acpi@...r.kernel.org, iommu@...ts.linux.dev, devicetree@...r.kernel.org
Subject: Re: [PATCH v3 6/7] iommu/dma: Centralise iommu_setup_dma_ops()

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@....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@...ux.intel.com>

Best regards,
baolu