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SubjectRe: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit
On Mon, Feb 07 2022 at 15:02, Fenghua Yu wrote:

> PASIDs are process wide. It was attempted to use refcounted PASIDs to
> free them when the last thread drops the refcount. This turned out to
> be complex and error prone. Given the fact that the PASID space is 20
> bits, which allows up to 1M processes to have a PASID associated
> concurrently, PASID resource exhaustion is not a realistic concern.
> Therefore it was decided to simplify the approach and stick with lazy
> on demand PASID allocation, but drop the eager free approach and make
> a allocated PASID lifetime bound to the life time of the process.
> Get rid of the refcounting mechanisms and replace/rename the interfaces
> to reflect this new approach.
> Suggested-by: Dave Hansen <>
> Signed-off-by: Fenghua Yu <>
> Reviewed-by: Tony Luck <>

Reviewed-by: Thomas Gleixner <>

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