[PATCH 2/2] iommu/vt-d: Make kernel parameter igfx_off work with vIOMMU

From: Lu Baolu
Date: Wed May 01 2019 - 21:41:17 EST

The kernel parameter igfx_off is used by users to disable
DMA remapping for the Intel integrated graphic device. It
was designed for bare metal cases where a dedicated IOMMU
is used for graphic. This doesn't apply to virtual IOMMU
case where an include-all IOMMU is used. This makes the
kernel parameter work with virtual IOMMU as well.

Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
Cc: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
Suggested-by: Kevin Tian <kevin.tian@xxxxxxxxx>
Fixes: c0771df8d5297 ("intel-iommu: Export a flag indicating that the IOMMU is used for iGFX.")
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Tested-by: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx>
drivers/iommu/intel-iommu.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 00ad00193883..e078b13ce3d8 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3415,9 +3415,12 @@ static int __init init_dmars(void)
iommu_identity_mapping |= IDENTMAP_ALL;

- iommu_identity_mapping |= IDENTMAP_GFX;
+ dmar_map_gfx = 0;

+ if (!dmar_map_gfx)
+ iommu_identity_mapping |= IDENTMAP_GFX;

if (iommu_identity_mapping) {