2 files changed, 19 insertions, 0 deletions

diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
index 17e0f77c7dad..fb4afd6d357d 100644
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -141,6 +141,8 @@ int amd_iommus_present;
 bool amd_iommu_np_cache __read_mostly;
 bool amd_iommu_iotlb_sup __read_mostly = true;
 
+u32 amd_iommu_max_pasids __read_mostly = ~0;
+
 /*
  * The ACPI table parsing functions set this variable on an error
  */
@@ -699,6 +701,17 @@ static void __init init_iommu_from_pci(struct amd_iommu *iommu)
 
         iommu->features = ((u64)high << 32) | low;
 
+        if (iommu_feature(iommu, FEATURE_GT)) {
+                u32 pasids;
+                u64 shift;
+
+                shift   = iommu->features & FEATURE_PASID_MASK;
+                shift >>= FEATURE_PASID_SHIFT;
+                pasids  = (1 << shift);
+
+                amd_iommu_max_pasids = min(amd_iommu_max_pasids, pasids);
+        }
+
         if (!is_rd890_iommu(iommu->dev))
                 return;
 
diff --git a/drivers/iommu/amd_iommu_types.h b/drivers/iommu/amd_iommu_types.h
index f8dd9ae693d1..0d984ca925be 100644
--- a/drivers/iommu/amd_iommu_types.h
+++ b/drivers/iommu/amd_iommu_types.h
@@ -87,6 +87,9 @@
 #define FEATURE_HE              (1ULL<<8)
 #define FEATURE_PC              (1ULL<<9)
 
+#define FEATURE_PASID_SHIFT     32
+#define FEATURE_PASID_MASK      (0x1fULL << FEATURE_PASID_SHIFT)
+
 /* MMIO status bits */
 #define MMIO_STATUS_COM_WAIT_INT_MASK   0x04
 
@@ -549,6 +552,9 @@ extern unsigned long *amd_iommu_pd_alloc_bitmap;
  */
 extern bool amd_iommu_unmap_flush;
 
+/* Smallest number of PASIDs supported by any IOMMU in the system */
+extern u32 amd_iommu_max_pasids;
+
 /* takes bus and device/function and returns the device id
  * FIXME: should that be in generic PCI code? */
 static inline u16 calc_devid(u8 bus, u8 devfn)