x86/amd-iommu: Fall back to GART if initialization fails

commit d7f0776975334070a93370ae048fda0c31a91c38 upstream.

This patch implements a fallback to the GART IOMMU if this
is possible and the AMD IOMMU initialization failed.
Otherwise the fallback would be nommu which is very
problematic on machines with more than 4GB of memory or
swiotlb which hurts io-performance.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index 2e775169bdf0b3bdd6f9e47d139358741bae84f6..bbef34ed4d028fa7c08f0115ce4f4b4dccab0c9f 100644 (file)
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -2256,10 +2256,6 @@ int __init amd_iommu_init_dma_ops(void)
 
        iommu_detected = 1;
        swiotlb = 0;
-#ifdef CONFIG_GART_IOMMU
-       gart_iommu_aperture_disabled = 1;
-       gart_iommu_aperture = 0;
-#endif
 
        /* Make the driver finally visible to the drivers */
        dma_ops = &amd_iommu_dma_ops;

diff --git a/arch/x86/kernel/amd_iommu_init.c b/arch/x86/kernel/amd_iommu_init.c
index fdce84d494592b83fa46f63e55413cf0ebc1da54..86a5a1178076bc255a0e4a0e9f425ffbfc2cdaf9 100644 (file)
--- a/arch/x86/kernel/amd_iommu_init.c
+++ b/arch/x86/kernel/amd_iommu_init.c
@@ -1340,6 +1340,15 @@ free:
 
        free_unity_maps();
 
+#ifdef CONFIG_GART_IOMMU
+       /*
+        * We failed to initialize the AMD IOMMU - try fallback to GART
+        * if possible.
+        */
+       gart_iommu_init();
+
+#endif
+
        goto out;
 }