linux-kernel - Re: [PATCH 2/5] iommu: Call helper function to get assigned pasid value

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Message-ID: <ZNUQtluLWek3PnEn@ziepe.ca>
Date:   Thu, 10 Aug 2023 13:30:46 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     "Tian, Kevin" <kevin.tian@...el.com>,
        "Zhang, Tina" <tina.zhang@...el.com>,
        Michael Shavit <mshavit@...gle.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] iommu: Call helper function to get assigned pasid
 value

On Thu, Aug 10, 2023 at 09:37:09AM +0800, Baolu Lu wrote:

> > The core could put the mm_notifier in a common iommu_domain_sva struct
> > and it could stick in the driver's invalidate ops, that would be a
> > nice simplification (and discourage drivers from doing the crazy
> > things they are currently doing)
> 
> Yes. So the iommu driver can retrieve the sva domain from struct
> mmu_notifier. The callback implementation will still be domain centric.
> Hence, there will be no need to use mm.

Remember the driver always needs the mm as it has to extract the page
table address from it.

At the end of the day installing the notifier is a single call in the
SVA alloc op, so it may not be worth optimizing beyond allowing
drivers to do it in their SVA alloc op.

Jason