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 23ebe34ff901e887cb72a9ab735520c7148e4091..f4efb4f78f917d2ebde255ac9ac20f8828edf686 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2103,6 +2103,8 @@
                        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.
                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 5c8c5cdc36cf565a74d49fc94724639414dc279d..9a9c6cdeed8d989cbda406c1f0c2dac7aaf87105 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) ((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)
@@ -287,12 +290,14 @@ 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 intel_iommu_superpage = 1;
 static int iommu_identity_mapping;
 static int iommu_skip_te_disable;
 
 #define IDENTMAP_GFX           2
 #define IDENTMAP_AZALIA                4
+#define IDENTMAP_INTGPU                8
 
 const struct iommu_ops intel_iommu_ops;
 
@@ -331,6 +336,9 @@ 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", 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;
@@ -2548,6 +2556,9 @@ 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;
@@ -2855,6 +2866,9 @@ 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);