[PATCH v2 01/12] iommu/vt-d: Disable superpage for Geminilake igfx

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

Geminilake igfx seems to have problems with superpage.

While running "gem_exec_big --r single" from igt-gpu-tools as soon
as a 2M mapping is made I tend to get a DMAR write fault. Strangely
the faulting address is always a 4K page and usually very far away
from the 2M page that got mapped. Regarless if no 2M mappings get
used I can't reproduce the fault.

I also tried to dump the PTE for the faulting address but it actually
looks correct to me (ie. definitely seems to have the write bit set):
 DMAR: DRHD: handling fault status reg 2
 DMAR: [DMA Write] Request device [00:02.0] PASID ffffffff fault addr 7fa8a78000 [fault reason 05] PTE Write access is not set
 DMAR: fault 7fa8a78000 (level=1) PTE = 149efc003

So not really sure what's going on, and this might just be full on duct
tape, but it seems to work here.

TODO: might be nice to disable superpage only for the igfx iommu
      instead of both iommus

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/iommu/intel/iommu.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 19c7888cbb86..4fff2c9c86af 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -5617,6 +5617,16 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x1632, quirk_iommu_igfx);
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x163A, quirk_iommu_igfx);
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x163D, quirk_iommu_igfx);
 
+static void quirk_iommu_nosp(struct pci_dev *dev)
+{
+	pci_info(dev, "Disabling IOMMU superpage for graphics on this chipset\n");
+	intel_iommu_superpage = 0;
+}
+
+/* Geminilake igfx appears to have issues with superpage */
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x3184, quirk_iommu_nosp);
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x3185, quirk_iommu_nosp);
+
 static void quirk_iommu_rwbf(struct pci_dev *dev)
 {
 	if (risky_device(dev))
-- 
2.31.1