[PATCH] iommu/amd: Add support for HTRangeIgnore feature

[Sairaj Kodilkar <sarunkod@amd.com>]

AMD IOMMU reserves the address range 0xfd00000000-0xffffffffff for
the hypertransport protocol (HT) and has special meaning. Hence devices
cannot use this address range for the DMA. However on some AMD platforms
this HT range is shifted to the very top of the address space and new
feature bit `HTRangeIgnore` is introduced. When this feature bit is on,
IOMMU treats the GPA access to the legacy HT range as regular GPA access.

Signed-off-by: Sairaj Kodilkar <sarunkod@amd.com>
---
 drivers/iommu/amd/amd_iommu.h       | 2 ++
 drivers/iommu/amd/amd_iommu_types.h | 1 +
 drivers/iommu/amd/init.c            | 5 +++++
 drivers/iommu/amd/iommu.c           | 3 +++
 4 files changed, 11 insertions(+)

diff --git a/drivers/iommu/amd/amd_iommu.h b/drivers/iommu/amd/amd_iommu.h
index 68debf5ee2d7..156eb66caca1 100644
--- a/drivers/iommu/amd/amd_iommu.h
+++ b/drivers/iommu/amd/amd_iommu.h
@@ -148,6 +148,8 @@ static inline int get_pci_sbdf_id(struct pci_dev *pdev)
 	return PCI_SEG_DEVID_TO_SBDF(seg, devid);
 }
 
+bool amd_iommu_ht_range_ignore(void);
+
 /*
  * This must be called after device probe completes. During probe
  * use rlookup_amd_iommu() get the iommu.
diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index 23caea22f8dc..1b3fc25bcdbf 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -111,6 +111,7 @@
 #define FEATURE_SNPAVICSUP	GENMASK_ULL(7, 5)
 #define FEATURE_SNPAVICSUP_GAM(x) \
 	(FIELD_GET(FEATURE_SNPAVICSUP, x) == 0x1)
+#define FEATURE_HT_RANGE_IGNORE		BIT_ULL(11)
 
 /* Note:
  * The current driver only support 16-bit PASID.
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index cb536d372b12..538af5a7418f 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -258,6 +258,11 @@ int amd_iommu_get_num_iommus(void)
 	return amd_iommus_present;
 }
 
+bool amd_iommu_ht_range_ignore(void)
+{
+	return check_feature2(FEATURE_HT_RANGE_IGNORE);
+}
+
 /*
  * Iterate through all the IOMMUs to get common EFR
  * masks among all IOMMUs and warn if found inconsistency.
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index cd5116d8c3b2..4985855914a3 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -2907,6 +2907,9 @@ static void amd_iommu_get_resv_regions(struct device *dev,
 		return;
 	list_add_tail(&region->list, head);
 
+	if (amd_iommu_ht_range_ignore())
+		return;
+
 	region = iommu_alloc_resv_region(HT_RANGE_START,
 					 HT_RANGE_END - HT_RANGE_START + 1,
 					 0, IOMMU_RESV_RESERVED, GFP_KERNEL);
-- 
2.34.1