[Intel-gfx] [PATCH v2 04/10] iommu/vt-d: Assume BIOS lies about ATSR for integrated gfx

[David Woodhouse]

If the device itself reports ATS in its PCIe capabilities, but the BIOS
neglects to provide an ATSR structure to indicate that the root port can
also cope, then assume the latter is lying.

Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
---
 drivers/iommu/intel-iommu.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 7136dc4..4a81523b 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1447,9 +1447,14 @@ iommu_support_dev_iotlb (struct dmar_domain *domain, struct intel_iommu *iommu,
 	if (!pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ATS))
 		return NULL;
 
-	if (!dmar_find_matched_atsr_unit(pdev))
-		return NULL;
-
+	if (!dmar_find_matched_atsr_unit(pdev)) {
+		if (intel_iommu_pasid28 && IS_GFX_DEVICE(pdev) &&
+		    pdev->vendor == 0x8086) {
+			pr_warn("BIOS denies ATSR capability for %s; assuming it lies\n",
+				dev_name(info->dev));
+		} else
+			return NULL;
+	}
 	return info;
 }
 
-- 
2.4.3

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse at intel.com                              Intel Corporation
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