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=igpu_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 f6a1513dfb76c0a54c43049f6cae91e312cf22bc..7c6c997dba18f6c70c33712c0cad4965e81fc78c 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1854,6 +1854,8 @@
                        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.
                forcedac [X86-64]
                        With this option iommu will not optimize to look
                        for io virtual address below 32-bit forcing dual

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 151243fa01ba58582899bb4aa986f3995efda99f..735f726097782b4d6310a13ff2010d44da27a02d 100644 (file)
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -54,6 +54,9 @@
 #define CONTEXT_SIZE           VTD_PAGE_SIZE
 
 #define IS_GFX_DEVICE(pdev) ((pdev->class >> 16) == PCI_BASE_CLASS_DISPLAY)
+#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)
@@ -351,6 +354,7 @@ int intel_iommu_enabled = 0;
 EXPORT_SYMBOL_GPL(intel_iommu_enabled);
 
 static int dmar_map_gfx = 1;
+static int dmar_map_intgpu = 1;
 static int dmar_forcedac;
 static int intel_iommu_strict;
 static int intel_iommu_superpage = 1;
@@ -360,6 +364,7 @@ static int iommu_skip_te_disable;
 
 #define IDENTMAP_GFX           2
 #define IDENTMAP_AZALIA                4
+#define IDENTMAP_INTGPU                8
 
 int intel_iommu_gfx_mapped;
 EXPORT_SYMBOL_GPL(intel_iommu_gfx_mapped);
@@ -445,6 +450,9 @@ static int __init intel_iommu_setup(char *str)
                } else if (!strncmp(str, "igfx_off", 8)) {
                        dmar_map_gfx = 0;
                        pr_info("Disable GFX device mapping\n");
+               } else if (!strncmp(str, "intgpu_off", 8)) {
+                       dmar_map_intgpu = 0;
+                       pr_info("Disable integrated GPU device mapping\n");
                } else if (!strncmp(str, "forcedac", 8)) {
                        pr_info("Forcing DAC for PCI devices\n");
                        dmar_forcedac = 1;
@@ -2940,6 +2948,9 @@ static int device_def_domain_type(struct device *dev)
 
                if ((iommu_identity_mapping & IDENTMAP_GFX) && IS_GFX_DEVICE(pdev))
                        return IOMMU_DOMAIN_IDENTITY;
+
+               if ((iommu_identity_mapping & IDENTMAP_INTGPU) && IS_INTGPU_DEVICE(pdev))
+                       return IOMMU_DOMAIN_IDENTITY;
        }
 
        return 0;
@@ -3375,6 +3386,9 @@ static int __init init_dmars(void)
        if (!dmar_map_gfx)
                iommu_identity_mapping |= IDENTMAP_GFX;
 
+       if (!dmar_map_intgpu)
+               iommu_identity_mapping |= IDENTMAP_INTGPU;
+
        check_tylersburg_isoch();
 
        ret = si_domain_init(hw_pass_through);