intel-iommu: Add option to exclude integrated GPU only

Bug-Debian: https://bugs.debian.org/935270
Bug-Kali: https://bugs.kali.org/view.php?id=5644

There is still laptop firmware that touches the integrated GPU behind
the operating system's back, and doesn't say so in the RMRR table.
Enabling the IOMMU for all devices causes breakage, but turning it off
for all graphics devices seems like a major weakness.

Add an option, intel_iommu=intgpu_off, to exclude only integrated GPUs
from remapping.  This is a narrower exclusion than igfx_off: it only
affects Intel devices on the root bus.  Devices attached through an
external port (Thunderbolt or ExpressCard) won't be on the root bus.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Gbp-Pq: Topic features/x86
Gbp-Pq: Name intel-iommu-add-option-to-exclude-integrated-gpu-only.patch

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index aa0031108bc1da46f32fb2f26f106a4232c104aa..a94aa88a4dbb1e66914e76a8327408deee3ab8da 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2490,6 +2490,8 @@ Kernel parameters
                        bypassed by not enabling DMAR with this option. In
                        this case, gfx device will use physical address for
                        DMA.
+               intgpu_off [Default Off]
+                       Bypass the DMAR unit for an integrated GPU only.
                strict [Default Off]
                        Deprecated, equivalent to iommu.strict=1.
                sp_off [Default Off]

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 705828b06e329ce5164ae4a78737ac68d02d65a9..9be8e122320d87f07d602bf46022d8b4d797cfa0 100644 (file)
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -35,6 +35,9 @@
 #define CONTEXT_SIZE           VTD_PAGE_SIZE
 
 #define IS_GFX_DEVICE(pdev) pci_is_display(pdev)
+#define IS_INTGPU_DEVICE(pdev) (IS_GFX_DEVICE(pdev) &&         \
+                               (pdev)->vendor == 0x8086 &&     \
+                               pci_is_root_bus((pdev)->bus))
 #define IS_USB_DEVICE(pdev) ((pdev->class >> 8) == PCI_CLASS_SERIAL_USB)
 #define IS_ISA_DEVICE(pdev) ((pdev->class >> 8) == PCI_CLASS_BRIDGE_ISA)
 #define IS_AZALIA(pdev) ((pdev)->vendor == 0x8086 && (pdev)->device == 0x3a3e)
@@ -202,12 +205,14 @@ int intel_iommu_sm = IS_ENABLED(CONFIG_INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON);
 int intel_iommu_enabled = 0;
 EXPORT_SYMBOL_GPL(intel_iommu_enabled);
 
+static int dmar_map_intgpu = 1;
 static int intel_iommu_superpage = 1;
 static int iommu_identity_mapping;
 static int iommu_skip_te_disable;
 static int disable_igfx_iommu;
 
 #define IDENTMAP_AZALIA                4
+#define IDENTMAP_INTGPU                8
 
 const struct iommu_ops intel_iommu_ops;
 
@@ -246,6 +251,9 @@ static int __init intel_iommu_setup(char *str)
                } else if (!strncmp(str, "igfx_off", 8)) {
                        disable_igfx_iommu = 1;
                        pr_info("Disable GFX device mapping\n");
+               } else if (!strncmp(str, "intgpu_off", 10)) {
+                       dmar_map_intgpu = 0;
+                       pr_info("Disable integrated GPU device mapping\n");
                } else if (!strncmp(str, "forcedac", 8)) {
                        pr_warn("intel_iommu=forcedac deprecated; use iommu.forcedac instead\n");
                        iommu_dma_forcedac = true;
@@ -1398,6 +1406,9 @@ static int device_def_domain_type(struct device *dev)
 
                if ((iommu_identity_mapping & IDENTMAP_AZALIA) && IS_AZALIA(pdev))
                        return IOMMU_DOMAIN_IDENTITY;
+
+               if ((iommu_identity_mapping & IDENTMAP_INTGPU) && IS_INTGPU_DEVICE(pdev))
+                       return IOMMU_DOMAIN_IDENTITY;
        }
 
        return 0;
@@ -1688,6 +1699,9 @@ static int __init init_dmars(void)
                iommu_set_root_entry(iommu);
        }
 
+       if (!dmar_map_intgpu)
+               iommu_identity_mapping |= IDENTMAP_INTGPU;
+
        check_tylersburg_isoch();
 
        /*