Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit

Joerg Roedel
2022-02-15T09:55:28Z

On Mon, Feb 07, 2022 at 03:02:48PM -0800, 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 <dave.hansen@linux.intel.com>
> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
> Reviewed-by: Tony Luck <tony.luck@intel.com>

Acked-by: Joerg Roedel <jroedel@suse.de>