linux-kernel - [PATCH 2/2] iommu/vt-d: Make kernel parameter igfx

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Date:   Thu,  2 May 2019 09:34:26 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>
Cc:     ashok.raj@...el.com, jacob.jun.pan@...el.com, kevin.tian@...el.com,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: [PATCH 2/2] iommu/vt-d: Make kernel parameter igfx_off work with vIOMMU

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@...el.com>
Cc: Jacob Pan <jacob.jun.pan@...ux.intel.com>
Suggested-by: Kevin Tian <kevin.tian@...el.com>
Fixes: c0771df8d5297 ("intel-iommu: Export a flag indicating that the IOMMU is used for iGFX.")
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
Tested-by: Zhenyu Wang <zhenyuw@...ux.intel.com>
---
 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;
 
 #ifdef CONFIG_INTEL_IOMMU_BROKEN_GFX_WA
-	iommu_identity_mapping |= IDENTMAP_GFX;
+	dmar_map_gfx = 0;
 #endif
 
+	if (!dmar_map_gfx)
+		iommu_identity_mapping |= IDENTMAP_GFX;
+
 	check_tylersburg_isoch();
 
 	if (iommu_identity_mapping) {
-- 
2.17.1