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 <kevmi...@arista.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