linux-kernel - Re: [PATCH v6 06/25] iommufd/access: Allow access->ops to be NULL for internal use

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Message-ID: <aFPU9TKgU0Lofl-O@google.com>
Date: Thu, 19 Jun 2025 09:14:29 +0000
From: Pranjal Shrivastava <praan@...gle.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: Jason Gunthorpe <jgg@...dia.com>, kevin.tian@...el.com, corbet@....net,
	will@...nel.org, bagasdotme@...il.com, robin.murphy@....com,
	joro@...tes.org, thierry.reding@...il.com, vdumpa@...dia.com,
	jonathanh@...dia.com, shuah@...nel.org, jsnitsel@...hat.com,
	nathan@...nel.org, peterz@...radead.org, yi.l.liu@...el.com,
	mshavit@...gle.com, zhangzekun11@...wei.com, iommu@...ts.linux.dev,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org,
	linux-kselftest@...r.kernel.org, patches@...ts.linux.dev,
	mochs@...dia.com, alok.a.tiwari@...cle.com, vasant.hegde@....com,
	dwmw2@...radead.org, baolu.lu@...ux.intel.com
Subject: Re: [PATCH v6 06/25] iommufd/access: Allow access->ops to be NULL
 for internal use

On Mon, Jun 16, 2025 at 07:21:28PM -0700, Nicolin Chen wrote:
> On Mon, Jun 16, 2025 at 10:33:05AM -0300, Jason Gunthorpe wrote:
> > On Sat, Jun 14, 2025 at 12:14:31AM -0700, Nicolin Chen wrote:
> > > @@ -1321,7 +1328,7 @@ int iommufd_access_pin_pages(struct iommufd_access *access, unsigned long iova,
> > >  
> > >  	/* Driver's ops don't support pin_pages */
> > >  	if (IS_ENABLED(CONFIG_IOMMUFD_TEST) &&
> > > -	    WARN_ON(access->iova_alignment != PAGE_SIZE || !access->ops->unmap))
> > > +	    WARN_ON(access->iova_alignment != PAGE_SIZE))
> > >  		return -EINVAL;
> > 
> > I don't want to loose this check, continuing blocking mdevs is still
> > important. Only the internal access should be able to use this
> > mechanism.
> 
> OK. So, it probably should be 
> 	if (IS_ENABLED(CONFIG_IOMMUFD_TEST) &&
> 	    WARN_ON(access->iova_alignment != PAGE_SIZE ||
> 		    (access->ictx && !access->ops->unmap))
> 

Nit: Probably worth mentioning in a comment that access->ops shouldn't
be NULL during selftests and hence we avoid checking for !access->ops?

If you feel it's too verbose, you can let be as well.

Reviewed-by: Pranjal Shrivastava <praan@...gle.com>

> Thanks
> Nicolin