linux-kernel - [PATCH] iommu: __iommu_attach_group: check for non-NULL blocking

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Message-ID: <9a3ebe9b-518e-49ef-b87d-925d951a446f@kernel.org>
Date: Mon, 29 Sep 2025 10:23:47 +0200
From: Hans Verkuil <hverkuil+cisco@...nel.org>
To: iommu@...ts.linux.dev
Cc: Linux Kernel <linux-kernel@...r.kernel.org>,
 Linux Media Mailing List <linux-media@...r.kernel.org>,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Jason Gunthorpe <jgg@...dia.com>, Jason Gunthorpe <jgg@...dia.com>
Subject: [PATCH] iommu: __iommu_attach_group: check for non-NULL
 blocking_domain

Loading the omap3isp driver fails in __iommu_attach_group:
group->blocking_domain is NULL, and so the check
group->domain != group->blocking_domain is always true and it
returns -EBUSY.

Only return -EBUSY if group->blocking_domain is non-NULL.

Signed-off-by: Hans Verkuil <hverkuil+cisco@...nel.org>
Fixes: 0286300e6045 ("iommu: iommu_group_claim_dma_owner() must always assign a domain")
---
Since I am unfamiliar with the iommu core code, I am uncertain whether I am
just papering over a bug elsewhere, or whether this is really the correct solution.

The omap3isp code in question is here:

drivers/media/platform/ti/omap3isp/isp.c, function isp_attach_iommu().

This omap3isp code predates the addition of blocking_domain and it used to work
before that feature was added.

I've tested this patch with my Beagle XM board.

If this patch is addressing the issue in the wrong place, then advise
on what the correct solution is would be very much appreciated!

I have a bunch of media omap3isp cleanup patches pending, but there is no point in
posting those until this issue is resolved.

Regards,

	Hans
---
 drivers/iommu/iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 060ebe330ee1..0ab1671ee850 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2220,7 +2220,7 @@ static int __iommu_attach_group(struct iommu_domain *domain,
 	struct device *dev;

 	if (group->domain && group->domain != group->default_domain &&
-	    group->domain != group->blocking_domain)
+	    group->blocking_domain && group->domain != group->blocking_domain)
 		return -EBUSY;

 	dev = iommu_group_first_dev(group);
-- 
2.47.2