linux-kernel - Re: [PATCH v5 09/29] iommufd: Do not unmap an owned iopt

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Message-ID: <aDdQ78ZPXexJILR4@Asurada-Nvidia>
Date: Wed, 28 May 2025 11:07:43 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: Jason Gunthorpe <jgg@...dia.com>
CC: <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>,
	<praan@...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 v5 09/29] iommufd: Do not unmap an owned iopt_area

On Wed, May 28, 2025 at 02:08:45PM -0300, Jason Gunthorpe wrote:
> Fundamentally this is supporting accesses that don't have an unmap op
> callback.

Ah, I see.

> It could be done differently, with the below just create your access
> with a null ops. Prevent mdev drivers from doing this when they create
> their accesses. We don't need to optimize this failure case so it is
> fine to scan the xarray. All we really need to do here is eliminate
> the WARN_ON.

Yes. That approach looks much cleaner.

Will replace the iopt_pin_pages patch.

Thanks
Nicolin