iommu/amd: Fix logic to determine and checking max PASID

In reality, the spec can only support 16-bit PASID since
INVALIDATE_IOTLB_PAGES and COMPLETE_PPR_REQUEST commands only allow 16-bit
PASID. So, we updated the PASID_MASK accordingly and invoke BUG_ON
if the hardware is reporting PASmax more than 16-bit.

Besides, max PASID is defined as ((2^(PASmax+1)) - 1). The current does not
determine this correctly.
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Tested-by: Jay Cornwall <Jay.Cornwall@amd.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>

drivers/iommu/amd_iommu.c

@@ -963,7 +963,7 @@ static void build_inv_iommu_pasid(struct iommu_cmd *cmd, u16 domid, int pasid,
 
 	address &= ~(0xfffULL);
 
-	cmd->data[0]  = pasid & PASID_MASK;
+	cmd->data[0]  = pasid;
 	cmd->data[1]  = domid;
 	cmd->data[2]  = lower_32_bits(address);
 	cmd->data[3]  = upper_32_bits(address);
@@ -1001,7 +1001,7 @@ static void build_complete_ppr(struct iommu_cmd *cmd, u16 devid, int pasid,
 
 	cmd->data[0]  = devid;
 	if (gn) {
-		cmd->data[1]  = pasid & PASID_MASK;
+		cmd->data[1]  = pasid;
 		cmd->data[2]  = CMD_INV_IOMMU_PAGES_GN_MASK;
 	}
 	cmd->data[3]  = tag & 0x1ff;

drivers/iommu/amd_iommu_init.c

@@ -150,7 +150,7 @@ 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;
+u32 amd_iommu_max_pasid __read_mostly = ~0;
 
 bool amd_iommu_v2_present __read_mostly;
 bool amd_iommu_pc_present __read_mostly;
@@ -1231,14 +1231,16 @@ static int iommu_init_pci(struct amd_iommu *iommu)
 
 	if (iommu_feature(iommu, FEATURE_GT)) {
 		int glxval;
-		u32 pasids;
-		u64 shift;
+		u32 max_pasid;
+		u64 pasmax;
 
-		shift   = iommu->features & FEATURE_PASID_MASK;
-		shift >>= FEATURE_PASID_SHIFT;
-		pasids  = (1 << shift);
+		pasmax = iommu->features & FEATURE_PASID_MASK;
+		pasmax >>= FEATURE_PASID_SHIFT;
+		max_pasid  = (1 << (pasmax + 1)) - 1;
 
-		amd_iommu_max_pasids = min(amd_iommu_max_pasids, pasids);
+		amd_iommu_max_pasid = min(amd_iommu_max_pasid, max_pasid);
+
+		BUG_ON(amd_iommu_max_pasid & ~PASID_MASK);
 
 		glxval   = iommu->features & FEATURE_GLXVAL_MASK;
 		glxval >>= FEATURE_GLXVAL_SHIFT;

drivers/iommu/amd_iommu_types.h

@@ -98,7 +98,12 @@
 #define FEATURE_GLXVAL_SHIFT	14
 #define FEATURE_GLXVAL_MASK	(0x03ULL << FEATURE_GLXVAL_SHIFT)
 
-#define PASID_MASK		0x000fffff
+/* Note:
+ * The current driver only support 16-bit PASID.
+ * Currently, hardware only implement upto 16-bit PASID
+ * even though the spec says it could have upto 20 bits.
+ */
+#define PASID_MASK		0x0000ffff
 
 /* MMIO status bits */
 #define MMIO_STATUS_EVT_INT_MASK	(1 << 1)
@@ -696,8 +701,8 @@ extern unsigned long *amd_iommu_pd_alloc_bitmap;
  */
 extern u32 amd_iommu_unmap_flush;
 
-/* Smallest number of PASIDs supported by any IOMMU in the system */
-extern u32 amd_iommu_max_pasids;
+/* Smallest max PASID supported by any IOMMU in the system */
+extern u32 amd_iommu_max_pasid;
 
 extern bool amd_iommu_v2_present;