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Date: Wed, 30 Mar 2022 17:00:39 +0300
From: Tony Lindgren <tony@atomide.com>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Joerg Roedel <joro@8bytes.org>, Jason Gunthorpe <jgg@nvidia.com>,
	Christoph Hellwig <hch@infradead.org>,
	Ben Skeggs <bskeggs@redhat.com>, Kevin Tian <kevin.tian@intel.com>,
	Ashok Raj <ashok.raj@intel.com>, Will Deacon <will@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	Eric Auger <eric.auger@redhat.com>, Liu Yi L <yi.l.liu@intel.com>,
	Jacob jun Pan <jacob.jun.pan@intel.com>,
	David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
	Thierry Reding <thierry.reding@gmail.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	Christoph Hellwig <hch@lst.de>, linux-omap@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, regressions@lists.linux.dev
Subject: Re: [PATCH v4 8/9] iommu: Remove unused argument in
 is_attach_deferred
Message-ID: <YkRiawC2T9g+CHSJ@atomide.com>
References: <20220216025249.3459465-1-baolu.lu@linux.intel.com>
 <20220216025249.3459465-9-baolu.lu@linux.intel.com>
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In-Reply-To: <20220216025249.3459465-9-baolu.lu@linux.intel.com>

Hi,

* Lu Baolu <baolu.lu@linux.intel.com> [700101 02:00]:
> The is_attach_deferred iommu_ops callback is a device op. The domain
> argument is unnecessary and never used. Remove it to make code clean.

Looks like this causes a regression for at least drivers/iommu/omap-iommu.c.

To me it seems the issue is there is no is_attach_deferred implemented, so
we get a NULL pointer dereference at virtual address 00000008:

__iommu_probe_device from probe_iommu_group+0x2c/0x38
probe_iommu_group from bus_for_each_dev+0x74/0xbc
bus_for_each_dev from bus_iommu_probe+0x34/0x2e8
bus_iommu_probe from bus_set_iommu+0x80/0xc8
bus_set_iommu from omap_iommu_init+0x88/0xcc
omap_iommu_init from do_one_initcall+0x44/0x24c

Any ideas for a fix?

It would be good to fix this quickly so we don't end up with a broken
v5.18-rc1..

For reference, this is mainline commit 41bb23e70b50 ("iommu: Remove unused
argument in is_attach_deferred").

Regards,

Tony

#regzbot ^introduced 41bb23e70b50