linux-kernel - Re: [PATCH v2 3/4] iommu: Keep dev->iommu state consistent

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Message-ID: <20250305181435.GJ5011@ziepe.ca>
Date: Wed, 5 Mar 2025 14:14:35 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Robin Murphy <robin.murphy@....com>
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Hanjun Guo <guohanjun@...wei.com>,
	Sudeep Holla <sudeep.holla@....com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>, Russell King <linux@...linux.org.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Danilo Krummrich <dakr@...nel.org>,
	Stuart Yoder <stuyoder@...il.com>,
	Laurentiu Tudor <laurentiu.tudor@....com>,
	Nipun Gupta <nipun.gupta@....com>,
	Nikhil Agarwal <nikhil.agarwal@....com>,
	Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-acpi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	iommu@...ts.linux.dev, devicetree@...r.kernel.org,
	linux-pci@...r.kernel.org,
	Charan Teja Kalla <quic_charante@...cinc.com>
Subject: Re: [PATCH v2 3/4] iommu: Keep dev->iommu state consistent

On Fri, Feb 28, 2025 at 03:46:32PM +0000, Robin Murphy wrote:
> @@ -127,6 +128,7 @@ int of_iommu_configure(struct device *dev, struct device_node *master_np,
>  		mutex_unlock(&iommu_probe_device_lock);
>  		return 0;
>  	}
> +	dev_iommu_present = dev->iommu;

I feel like this deserves a comment..

Maybe it is:

/*
 * If of_iommu_configure is called outside the iommu probe path
 * dev->iommu should be NULL and it needs to remain as NULL
 * If it is called within the probe path then the dev->iommu
 * was setup by iommu_init_device() and must not be changed.
 */

And I think the commit message should explain what consistent
means.. AFAICT you are going for !dev->iommu means no probe has
succeed / dev->iommu means a probe is ongoing in this call chain or
it has succeeded?

Otherwise:

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Jason