Re: [PATCH 2/5] iommu: Ensure device has the same iommu_ops as the domain

From: Jason Gunthorpe <jgg@nvidia.com>
To: Nicolin Chen <nicolinc@nvidia.com>
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Subject: Re: [PATCH 2/5] iommu: Ensure device has the same iommu_ops as the domain
Date: Mon, 6 Jun 2022 15:52:23 -0300	[thread overview]
Message-ID: <20220606185223.GE1343366@nvidia.com> (raw)
In-Reply-To: <Yp5HYe51LSQke/GY@Asurada-Nvidia>

On Mon, Jun 06, 2022 at 11:28:49AM -0700, Nicolin Chen wrote:

> > Well, as before I'd prefer to make the code match the commit message -
> > if I really need to spell it out, see below - since I can't imagine that
> > we should ever have need to identify a set of iommu_domain_ops in
> > isolation, therefore I think it's considerably clearer to use the
> > iommu_domain itself. However, either way we really don't need this yet,
> > so we may as well just go ahead and remove the redundant test from VFIO
> > anyway, and I can add some form of this patch to my dev branch for now.
> 
> I see. The version below is much cleaner. Yet, it'd become having a
> common pointer per iommu_domain vs. one pointer per driver. Jason
> pointed it out to me earlier that by doing so memory waste would be
> unnecessary on platforms that have considerable numbers of masters.

I had ment using struct iommu_domain when there is a simple solution
to use rodata doesn't seem ideal.

I don't quite understand the reluctance to make small changes to
drivers, it was the same logic with the default_domain_ops thing too.

> Since we know that it'd be safe to exclude this single change from
> this series, I can drop it in next version, if you don't like the
> change.

But this is fine too, that really is half the point of this series..

Jason

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