Messages in this thread | | | Date | Mon, 14 Feb 2022 15:39:53 +0100 | From | Joerg Roedel <> | Subject | Re: [PATCH v1 3/8] iommu: Extend iommu_at[de]tach_device() for multi-device groups |
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On Mon, Feb 14, 2022 at 09:03:13AM -0400, Jason Gunthorpe wrote: > Groups should disappear into an internal implementation detail, not be > so prominent in the API.
Not going to happen, IOMMU groups are ABI and todays device assignment code, including user-space, relies on them.
Groups implement and important aspect of hardware IOMMUs that the API can not abstract away: That there are devices which share the same request-id.
This is not an issue for devices concerned by iommufd, but for legacy device assignment it is. The IOMMU-API needs to handle both in a clean API, even if it means that drivers need to lookup the sub-group of a device first.
And I don't see how a per-device API can handle both in a device-centric way. For sure it is not making it 'device centric but operate on groups under the hood'.
Regards,
Joerg
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