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

[Fenghua Yu]

On Tue, Feb 08, 2022 at 10:41:39AM +0800, Lu Baolu wrote:
> On 2/8/22 7:02 AM, 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@xxxxxxxxxxxxxxx>
> > Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
> > Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
> > ---
> > v4:
> > - Update the commit message (Thomas).
> 
> Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>

Thank you very much for your review, Baolu!

-Fenghua