Re: [PATCH v2 5/5] vfio/iommu_type1: Simplify group attachment

Jason Gunthorpe
2022-06-20T04:03:39Z

On Fri, Jun 17, 2022 at 04:07:20PM -0700, Nicolin Chen wrote:

> > > > > + vfio_iommu_aper_expand(iommu, &iova_copy);
> > > >
> > > > but now it's done for every group detach. The aperture is decided
> > > > by domain geometry which is not affected by attached groups.
> > >
> > > Yea, I've noticed this part. Actually Jason did this change for
> > > simplicity, and I think it'd be safe to do so?
> >
> > Perhaps detach_destroy() can return a Boolean to indicate whether
> > a domain is destroyed.
>
> It could be a solution but doesn't feel that common for a clean
> function to have a return value indicating a special case. Maybe
> passing in "&domain" so that we can check if it's NULL after?

It is harmless to do every time, it just burns a few CPU cycles on a
slow path. We don't need complexity to optmize it.

Jason