From 13609f1305289f9d8de53f44c8aa8edb44004332 Mon Sep 17 00:00:00 2001 From: Joerg Roedel Date: Fri, 1 Jul 2016 16:42:55 +0200 Subject: [PATCH] iommu/amd: Fix unity mapping initialization race There is a race condition in the AMD IOMMU init code that causes requested unity mappings to be blocked by the IOMMU for a short period of time. This results on boot failures and IO_PAGE_FAULTs on some machines. Fix this by making sure the unity mappings are installed before all other DMA is blocked. Fixes: 9fab0666a65b ('iommu/amd: Implement add_device and remove_device') Cc: stable@vger.kernel.org # v4.2+ Signed-off-by: Joerg Roedel --- drivers/iommu/amd_iommu_init.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c index d091defc34260..59741ead7e158 100644 --- a/drivers/iommu/amd_iommu_init.c +++ b/drivers/iommu/amd_iommu_init.c @@ -1568,13 +1568,23 @@ static int __init amd_iommu_init_pci(void) break; } + /* + * Order is important here to make sure any unity map requirements are + * fulfilled. The unity mappings are created and written to the device + * table during the amd_iommu_init_api() call. + * + * After that we call init_device_table_dma() to make sure any + * uninitialized DTE will block DMA, and in the end we flush the caches + * of all IOMMUs to make sure the changes to the device table are + * active. + */ + ret = amd_iommu_init_api(); + init_device_table_dma(); for_each_iommu(iommu) iommu_flush_all_caches(iommu); - ret = amd_iommu_init_api(); - if (!ret) print_iommu_info(); -- 2.39.5