linux-kernel - Re: [PATCH v2 3/7] iommu: Make iommu_dma_prepare

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Message-ID: <20250227194749.GJ39591@nvidia.com>
Date: Thu, 27 Feb 2025 15:47:49 -0400
From: Jason Gunthorpe <jgg@...dia.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: Robin Murphy <robin.murphy@....com>, kevin.tian@...el.com,
	tglx@...utronix.de, maz@...nel.org, joro@...tes.org,
	will@...nel.org, 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 3/7] iommu: Make iommu_dma_prepare_msi() into a
 generic operation

On Thu, Feb 27, 2025 at 09:46:55AM -0800, Nicolin Chen wrote:
> I found a bit confusing to use "owner" as the domain->owner isn't
> the same thing in this context. Maybe it should be "driver_ops"?

Maybe, but I wouldn't churn it

> Then, "owner" could be another op structure that holds the owner-
> specific things, such as:
> 	enum iommu_domain_owner { DMA/VFIO/IOMMUFD}; // or flag?

I was thinking about breaking type into something like this:

u32 private_data_owner:2 // DMA/IOMMUFD/None
u32 translation_type:3   // paging/identity/sva/platform/blocked/nested
u32 dma_fq:1             // true/false
u32 dma_api_domain:1     // true/false

Which is close to how it already is with just some breaking up of the
bits differently.. Get rid of the word unmanaged and drop the
IOMMU_DOMAIN_* defines.

I also wanted to separate the "policy" enum that determines which of
the three default domains you get from the type. Lots of type
combinations are not allowed as policy.

Jason