linux-kernel - [PATCH] vfio: Stop using iommu

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Message-Id: <537103bbd7246574f37f2c88704d7824a3a889f2.1649160714.git.robin.murphy@arm.com>
Date:   Tue,  5 Apr 2022 13:11:54 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     alex.williamson@...hat.com
Cc:     cohuck@...hat.com, iommu@...ts.linux-foundation.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] vfio: Stop using iommu_present()

IOMMU groups have been mandatory for some time now, so a device without
one is necessarily a device without any usable IOMMU, therefore the
iommu_present() check is redundant (or at best unhelpful).

Signed-off-by: Robin Murphy <robin.murphy@....com>
---
 drivers/vfio/vfio.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index a4555014bd1e..7b0a7b85e77e 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -745,11 +745,11 @@ static struct vfio_group *vfio_group_find_or_alloc(struct device *dev)
 
 	iommu_group = iommu_group_get(dev);
 #ifdef CONFIG_VFIO_NOIOMMU
-	if (!iommu_group && noiommu && !iommu_present(dev->bus)) {
+	if (!iommu_group && noiommu) {
 		/*
 		 * With noiommu enabled, create an IOMMU group for devices that
-		 * don't already have one and don't have an iommu_ops on their
-		 * bus.  Taint the kernel because we're about to give a DMA
+		 * don't already have one, implying no IOMMU hardware/driver
+		 * exists.  Taint the kernel because we're about to give a DMA
 		 * capable device to a user without IOMMU protection.
 		 */
 		group = vfio_noiommu_group_alloc(dev, VFIO_NO_IOMMU);
-- 
2.28.0.dirty