intel-iommu: Add option to exclude integrated GPU only

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 cb17fde4164ffafafbfe905571812b6dbb734021..04f14df03aed8ea144cd392a758b177d504fc6a9 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1699,6 +1699,8 @@
                        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 1ad24367373f416bf367d60b03da6b22b74bc297..c0ef649303352833dbe32396f2d19086779a4bc4 100644 (file)
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -52,6 +52,9 @@
 #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)
@@ -353,6 +356,7 @@ 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;
@@ -362,6 +366,7 @@ static int iommu_identity_mapping;
 #define IDENTMAP_ALL           1
 #define IDENTMAP_GFX           2
 #define IDENTMAP_AZALIA                4
+#define IDENTMAP_INTGPU                8
 
 #define sm_supported(iommu)    (intel_iommu_sm && ecap_smts((iommu)->ecap))
 #define pasid_supported(iommu) (sm_supported(iommu) &&                 \
@@ -440,6 +445,9 @@ 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;
@@ -2951,6 +2959,9 @@ static int iommu_should_identity_map(struct device *dev, int startup)
                if ((iommu_identity_mapping & IDENTMAP_GFX) && IS_GFX_DEVICE(pdev))
                        return 1;
 
+               if ((iommu_identity_mapping & IDENTMAP_INTGPU) && IS_INTGPU_DEVICE(pdev))
+                       return 1;
+
                if (!(iommu_identity_mapping & IDENTMAP_ALL))
                        return 0;
 
@@ -3416,6 +3427,9 @@ 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();
 
        if (iommu_identity_mapping) {