The IORT table generator is setting up a reference to ID array for
nodes even when the ID Mapping count is zero. This is not an issue as an
OS would only access the ID Reference if the ID mapping count is not zero.

However, it would be good to set the reference to ID array to zero when
the ID Mapping count is zero rather than populating it with an incorrect
value.

Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Pierre Gondois <pierre.gondois@arm.com>
---

Notes:
    v2:
     - No code change since v1. Re-sending with v2 series.    [SAMI]
    
    v3:
     - No code change since v1. Re-sending with v3 series.    [SAMI]

 DynamicTablesPkg/Library/Acpi/Arm/AcpiIortLibArm/IortGenerator.c | 29 +++++++++++---------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/DynamicTablesPkg/Library/Acpi/Arm/AcpiIortLibArm/IortGenerator.c b/DynamicTablesPkg/Library/Acpi/Arm/AcpiIortLibArm/IortGenerator.c
index a1714dbedd3e34e2716e828092aac169461c43c9..46ff1e6d03852daa2058b8bd13f4b18f775aba6e 100644
--- a/DynamicTablesPkg/Library/Acpi/Arm/AcpiIortLibArm/IortGenerator.c
+++ b/DynamicTablesPkg/Library/Acpi/Arm/AcpiIortLibArm/IortGenerator.c
@@ -1,7 +1,7 @@
 /** @file
   IORT Table Generator
 
-  Copyright (c) 2017 - 2020, ARM Limited. All rights reserved.
+  Copyright (c) 2017 - 2021, Arm Limited. All rights reserved.
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
   @par Reference(s):
@@ -870,9 +870,9 @@ AddNamedComponentNodes (
     NcNode->Node.NumIdMappings = NodeList->IdMappingCount;
 
     ObjectNameLength = AsciiStrLen (NodeList->ObjectName) + 1;
-    NcNode->Node.IdReference =
-      (UINT32)(sizeof (EFI_ACPI_6_0_IO_REMAPPING_NAMED_COMP_NODE) +
-        (ALIGN_VALUE (ObjectNameLength, 4)));
+    NcNode->Node.IdReference = (NodeList->IdMappingCount == 0) ?
+      0 : ((UINT32)(sizeof (EFI_ACPI_6_0_IO_REMAPPING_NAMED_COMP_NODE) +
+           (ALIGN_VALUE (ObjectNameLength, 4))));
 
     // Named Component specific data
     NcNode->Flags = NodeList->Flags;
@@ -1001,7 +1001,8 @@ AddRootComplexNodes (
     RcNode->Node.Revision = 1;
     RcNode->Node.Reserved = EFI_ACPI_RESERVED_DWORD;
     RcNode->Node.NumIdMappings = NodeList->IdMappingCount;
-    RcNode->Node.IdReference = sizeof (EFI_ACPI_6_0_IO_REMAPPING_RC_NODE);
+    RcNode->Node.IdReference = (NodeList->IdMappingCount == 0) ?
+      0 : sizeof (EFI_ACPI_6_0_IO_REMAPPING_RC_NODE);
 
     // Root Complex specific data
     RcNode->CacheCoherent = NodeList->CacheCoherent;
@@ -1182,11 +1183,12 @@ AddSmmuV1V2Nodes (
     SmmuNode->Node.Revision = 0;
     SmmuNode->Node.Reserved = EFI_ACPI_RESERVED_DWORD;
     SmmuNode->Node.NumIdMappings = NodeList->IdMappingCount;
-    SmmuNode->Node.IdReference = sizeof (EFI_ACPI_6_0_IO_REMAPPING_SMMU_NODE) +
-      (NodeList->ContextInterruptCount *
-      sizeof (EFI_ACPI_6_0_IO_REMAPPING_SMMU_INT)) +
-      (NodeList->PmuInterruptCount *
-      sizeof (EFI_ACPI_6_0_IO_REMAPPING_SMMU_INT));
+    SmmuNode->Node.IdReference = (NodeList->IdMappingCount == 0) ?
+      0 : (sizeof (EFI_ACPI_6_0_IO_REMAPPING_SMMU_NODE) +
+           (NodeList->ContextInterruptCount *
+           sizeof (EFI_ACPI_6_0_IO_REMAPPING_SMMU_INT)) +
+           (NodeList->PmuInterruptCount *
+           sizeof (EFI_ACPI_6_0_IO_REMAPPING_SMMU_INT)));
 
     // SMMU v1/v2 specific data
     SmmuNode->Base = NodeList->BaseAddress;
@@ -1352,8 +1354,8 @@ AddSmmuV3Nodes (
     SmmuV3Node->Node.Revision = 2;
     SmmuV3Node->Node.Reserved = EFI_ACPI_RESERVED_DWORD;
     SmmuV3Node->Node.NumIdMappings = NodeList->IdMappingCount;
-    SmmuV3Node->Node.IdReference =
-      sizeof (EFI_ACPI_6_0_IO_REMAPPING_SMMU3_NODE);
+    SmmuV3Node->Node.IdReference = (NodeList->IdMappingCount == 0) ?
+      0 : sizeof (EFI_ACPI_6_0_IO_REMAPPING_SMMU3_NODE);
 
     // SMMUv3 specific data
     SmmuV3Node->Base = NodeList->BaseAddress;
@@ -1482,7 +1484,8 @@ AddPmcgNodes (
     PmcgNode->Node.Revision = 1;
     PmcgNode->Node.Reserved = EFI_ACPI_RESERVED_DWORD;
     PmcgNode->Node.NumIdMappings = NodeList->IdMappingCount;
-    PmcgNode->Node.IdReference = sizeof (EFI_ACPI_6_0_IO_REMAPPING_PMCG_NODE);
+    PmcgNode->Node.IdReference = (NodeList->IdMappingCount == 0) ?
+      0 : sizeof (EFI_ACPI_6_0_IO_REMAPPING_PMCG_NODE);
 
     // PMCG specific data
     PmcgNode->Base = NodeList->BaseAddress;
-- 
'Guid(CE165669-3EF3-493F-B85D-6190EE5B9759)'



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