linux-kernel - Re: [PATCH v3 5/8] iommu/arm-smmu-v3: Refactor write_ctx

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Message-ID: <ZMmaV+e6BtyJgn9R@nvidia.com>
Date:   Tue, 1 Aug 2023 20:50:47 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Michael Shavit <mshavit@...gle.com>
Cc:     iommu@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, robin.murphy@....com,
        will@...nel.org, jean-philippe@...aro.org, nicolinc@...dia.com
Subject: Re: [PATCH v3 5/8] iommu/arm-smmu-v3: Refactor write_ctx_desc

On Wed, Aug 02, 2023 at 02:35:22AM +0800, Michael Shavit wrote:
> Update arm_smmu_write_ctx_desc and downstream functions to operate on
> a master instead of an smmu domain. We expect arm_smmu_write_ctx_desc()
> to only be called to write a CD entry into a CD table owned by the
> master. Under the hood, arm_smmu_write_ctx_desc still fetches the CD
> table from the domain that is attached to the master, but a subsequent
> commit will move that table's ownership to the master.
> 
> Note that this change isn't a nop refactor since SVA will call
> arm_smmu_write_ctx_desc in a loop for every master the domain is
> attached to despite the fact that they all share the same CD table. This
> loop may look weird but becomes necessary when the CD table becomes
> per-master in a subsequent commit.
> 
> Signed-off-by: Michael Shavit <mshavit@...gle.com>
> ---
> 
> Changes in v3:
> - Add a helper to write a CD to all masters that a domain is attached
>   to.
> - Fixed an issue where an arm_smmu_write_ctx_desc error return wasn't
>   correctly handled by its caller.
> 
> Changes in v2:
> - minor style fixes
> 
> Changes in v1:
> - arm_smmu_write_ctx_desc now get's the CD table to write to from the
>   master parameter instead of a distinct parameter. This works well
>   because the CD table being written to should always be owned by the
>   master by the end of this series. This version no longer allows master
>   to be NULL.
> 
>  .../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c   | 31 +++++++++--
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   | 51 +++++++------------
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   |  2 +-
>  3 files changed, 46 insertions(+), 38 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Jason