linux-kernel - [PATCH 2/2] iommu: Don't use swiotlb unless it's active

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Date:   Mon, 4 Apr 2022 11:47:07 -0500
From:   Mario Limonciello <mario.limonciello@....com>
To:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>
CC:     Christoph Hellwig <hch@...radead.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        "open list:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        Suthikulpanit Suravee <Suravee.Suthikulpanit@....com>,
        Hegde Vasant <Vasant.Hegde@....com>,
        "open list" <linux-kernel@...r.kernel.org>,
        Mario Limonciello <mario.limonciello@....com>
Subject: [PATCH 2/2] iommu: Don't use swiotlb unless it's active

The helper function `dev_use_swiotlb` is used for various decision
making points for how to handle DMA mapping requests.

If the kernel doesn't have any memory allocated for swiotlb to use, then
an untrusted device being connected to the system may fail to initialize
when a request is made.

To avoid this situation, don't mark the use of swiotlb when it has not
been set up.

Signed-off-by: Mario Limonciello <mario.limonciello@....com>
---
 drivers/iommu/dma-iommu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 09f6e1c0f9c0..92ca136c8a12 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -504,7 +504,8 @@ static bool dev_is_untrusted(struct device *dev)
 
 static bool dev_use_swiotlb(struct device *dev)
 {
-	return IS_ENABLED(CONFIG_SWIOTLB) && dev_is_untrusted(dev);
+	return IS_ENABLED(CONFIG_SWIOTLB) && dev_is_untrusted(dev) \
+		&& is_swiotlb_active(dev);
 }
 
 /**
-- 
2.34.1