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

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Message-ID: <ZNOnOGTfpXzrrRTz@ziepe.ca>
Date:   Wed, 9 Aug 2023 11:48:24 -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 Wed, Aug 09, 2023 at 06:58:15PM +0800, Baolu Lu wrote:
> On 2023/8/9 17:49, Tian, Kevin wrote:
> > > From: Baolu Lu <baolu.lu@...ux.intel.com>
> > > Sent: Wednesday, August 9, 2023 8:22 AM
> > > 
> > > On 2023/8/8 15:49, Tina Zhang wrote:
> > > > Use the helper function mm_get_pasid() to get the mm assigned pasid
> > > > value.
> > > 
> > > For internal iommu drivers, perhaps we should use another helper.
> > > Something like sva_domain_get_pasid()?
> > > 
> > > Suppose that the iommu drivers should have no idea about the "mm".
> > > 
> > 
> > Aren't all touched functions accept a struct mm_struct pointer?
> 
> In the end we should remove all mm reference in the individual drivers.
> The drivers only need to know what they need to know. All mm-aware code
> should eventually be moved to the core.
> 
> For now, at least we should avoid using mm in the set/remove_dev_pasid
> code path. Later, once we complete consolidating mm notification in the
> core, drivers will have no need to use "mm" anymore.

I'm not sure how this will play out...

We don't want extra function indirections here so ultimately the
driver needs to hook the arch_invalidate_range() in the mm_notifier
with its own function.

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)

Jason