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 fb95fad81c79a065e728202a34a3dabac5653cb4..d387ff772ae590d535535c42f1685429788fca19 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1814,6 +1814,8 @@
                        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 04e82f1756010b8060ccd0d45916d316278589cd..7ae5ff8fe70da8cbe5a02231a90026bef52ebcb6 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);
@@ -447,6 +452,9 @@ 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;
@@ -2843,6 +2851,9 @@ 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;
@@ -3278,6 +3289,9 @@ 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);