linux-kernel - Re: [PATCH v2 2/7] genirq/msi: Refactor iommu_dma_compose_msi

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Message-ID: <87ikp3hcj3.ffs@tglx>
Date: Fri, 21 Feb 2025 10:28:48 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Nicolin Chen <nicolinc@...dia.com>, jgg@...dia.com,
 kevin.tian@...el.com, maz@...nel.org
Cc: joro@...tes.org, will@...nel.org, robin.murphy@....com,
 shuah@...nel.org, iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kselftest@...r.kernel.org,
 eric.auger@...hat.com, baolu.lu@...ux.intel.com, yi.l.liu@...el.com,
 yury.norov@...il.com, jacob.pan@...ux.microsoft.com,
 patches@...ts.linux.dev
Subject: Re: [PATCH v2 2/7] genirq/msi: Refactor iommu_dma_compose_msi_msg()

On Wed, Feb 19 2025 at 17:31, Nicolin Chen wrote:
> From: Jason Gunthorpe <jgg@...dia.com>
>
> The two-step process to translate the MSI address involves two functions,
> iommu_dma_prepare_msi() and iommu_dma_compose_msi_msg().
>
> Previously iommu_dma_compose_msi_msg() needed to be in the iommu layer as
> it had to dereference the opaque cookie pointer. Now, the previous patch
> changed the cookie pointer into an integer so there is no longer any need
> for the iommu layer to be involved.
>
> Further, the call sites of iommu_dma_compose_msi_msg() all follow the same
> pattern of setting an MSI message address_hi/lo to non-translated and then
> immediately calling iommu_dma_compose_msi_msg().
>
> Refactor iommu_dma_compose_msi_msg() into msi_msg_set_addr() that directly
> accepts the u64 version of the address and simplifies all the callers.
>
> Move the new helper to linux/msi.h since it has nothing to do with iommu.
>
> Aside from refactoring, this logically prepares for the next patch, which
> allows multiple implementation options for iommu_dma_prepare_msi(). So, it
> does not make sense to have the iommu_dma_compose_msi_msg() in dma-iommu.c
> as it no longer provides the only iommu_dma_prepare_msi() implementation.
>
> Signed-off-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>