linux-kernel - [PATCH 2/3] iommu/amd: move gart fallback to amd_iommu

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Message-Id: <20190528182958.3623-3-kevmitch@arista.com>
Date:   Tue, 28 May 2019 11:29:57 -0700
From:   Kevin Mitchell <kevmitch@...sta.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Kevin Mitchell <kevmitch@...sta.com>
Subject: [PATCH 2/3] iommu/amd: move gart fallback to amd_iommu_init

The fallback to the GART driver in the case amd_iommu doesn't work was
executed in a function called free_iommu_resources, which didn't really
make sense. This was even being called twice if amd_iommu=off was
specified on the command line.

The only complication is that it needs to be verified that amd_iommu has
fully relinquished control by calling free_iommu_resources and emptying
the amd_iommu_list.

Signed-off-by: Kevin Mitchell <kevmitch@...sta.com>
---
 drivers/iommu/amd_iommu_init.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
index 3798d7303c99..5f3df5ae6ba8 100644
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -2345,15 +2345,6 @@ static void __init free_iommu_resources(void)
 	amd_iommu_dev_table = NULL;
 
 	free_iommu_all();
-
-#ifdef CONFIG_GART_IOMMU
-	/*
-	 * We failed to initialize the AMD IOMMU - try fallback to GART
-	 * if possible.
-	 */
-	gart_iommu_init();
-
-#endif
 }
 
 /* SB IOAPIC is always on this device in AMD systems */
@@ -2774,6 +2765,16 @@ static int __init amd_iommu_init(void)
 		}
 	}
 
+#ifdef CONFIG_GART_IOMMU
+	if (ret && list_empty(&amd_iommu_list)) {
+		/*
+		 * We failed to initialize the AMD IOMMU - try fallback
+		 * to GART if possible.
+		 */
+		gart_iommu_init();
+	}
+#endif
+
 	for_each_iommu(iommu)
 		amd_iommu_debugfs_setup(iommu);
 
-- 
2.20.1