[PATCH v3 3/5] vfio/iommu_type1: Remove the domain->ops comparison

From: Nicolin Chen <nicolinc@nvidia.com>
To: <joro@8bytes.org>, <will@kernel.org>, <marcan@marcan.st>,
	<sven@svenpeter.dev>, <robin.murphy@arm.com>,
	<robdclark@gmail.com>, <baolu.lu@linux.intel.com>,
	<matthias.bgg@gmail.com>, <orsonzhai@gmail.com>,
	<baolin.wang7@gmail.com>, <zhang.lyra@gmail.com>,
	<jean-philippe@linaro.org>, <alex.williamson@redhat.com>,
	<jgg@nvidia.com>, <kevin.tian@intel.com>
Cc: mjrosato@linux.ibm.com, jordan@cosmicpenguin.net,
	thierry.reding@gmail.com, alyssa@rosenzweig.io,
	linux-s390@vger.kernel.org, kvm@vger.kernel.org,
	jonathanh@nvidia.com, yong.wu@mediatek.com,
	yangyingliang@huawei.com, gerald.schaefer@linux.ibm.com,
	linux-arm-msm@vger.kernel.org, john.garry@huawei.com,
	christophe.jaillet@wanadoo.fr, thunder.leizhen@huawei.com,
	linux-tegra@vger.kernel.org, tglx@linutronix.de,
	virtualization@lists.linux-foundation.org,
	linux-arm-kernel@lists.infradead.org, chenxiang66@hisilicon.com,
	cohuck@redhat.com, linux-kernel@vger.kernel.org,
	iommu@lists.linux-foundation.org, suravee.suthikulpanit@amd.com,
	linux-mediatek@lists.infradead.org, dwmw2@infradead.org
Subject: [PATCH v3 3/5] vfio/iommu_type1: Remove the domain->ops comparison
Date: Thu, 23 Jun 2022 13:00:27 -0700	[thread overview]
Message-ID: <20220623200029.26007-4-nicolinc@nvidia.com> (raw)
In-Reply-To: <20220623200029.26007-1-nicolinc@nvidia.com>

The domain->ops validation was added, as a precaution, for mixed-driver
systems.

Per Robin's remarks,
* While bus_set_iommu() still exists, the core code prevents multiple
  drivers from registering, so we can't really run into a situation of
  having a mixed-driver system:
  https://lore.kernel.org/kvm/6e1280c5-4b22-ebb3-3912-6c72bc169982@arm.com/

* And there's plenty more significant problems than this to fix; in future
  when many can be permitted, we will rely on the IOMMU core code to check
  the domain->ops:
  https://lore.kernel.org/kvm/6575de6d-94ba-c427-5b1e-967750ddff23@arm.com/

So remove the check in VFIO for simplicity.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
 drivers/vfio/vfio_iommu_type1.c | 32 +++++++++++---------------------
 1 file changed, 11 insertions(+), 21 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index f4e3b423a453..11be5f95580b 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -2277,29 +2277,19 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 			domain->domain->ops->enforce_cache_coherency(
 				domain->domain);
 
-	/*
-	 * Try to match an existing compatible domain.  We don't want to
-	 * preclude an IOMMU driver supporting multiple bus_types and being
-	 * able to include different bus_types in the same IOMMU domain, so
-	 * we test whether the domains use the same iommu_ops rather than
-	 * testing if they're on the same bus_type.
-	 */
+	/* Try to match an existing compatible domain */
 	list_for_each_entry(d, &iommu->domain_list, next) {
-		if (d->domain->ops == domain->domain->ops) {
-			iommu_detach_group(domain->domain, group->iommu_group);
-			if (!iommu_attach_group(d->domain,
-						group->iommu_group)) {
-				list_add(&group->next, &d->group_list);
-				iommu_domain_free(domain->domain);
-				kfree(domain);
-				goto done;
-			}
-
-			ret = iommu_attach_group(domain->domain,
-						 group->iommu_group);
-			if (ret)
-				goto out_domain;
+		iommu_detach_group(domain->domain, group->iommu_group);
+		if (!iommu_attach_group(d->domain, group->iommu_group)) {
+			list_add(&group->next, &d->group_list);
+			iommu_domain_free(domain->domain);
+			kfree(domain);
+			goto done;
 		}
+
+		ret = iommu_attach_group(domain->domain,  group->iommu_group);
+		if (ret)
+			goto out_domain;
 	}
 
 	vfio_test_domain_fgsp(domain);
-- 
2.17.1


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