[edk2-devel] [PATCH v4 1/1] MdeModulePkg/AcpiTableDxe: Prefer xDSDT over DSDT when installing tables

["Dhaval Sharma" <dhaval@rivosinc.com>]

As per ACPI Spec 6.5+ Table 5-9 if xDSDT is available,
it should be used first. Handle required flow when xDSDT
is absent or present.

Test: Tested on RISCV64 Qemu platform with xDSDT and booted to
linux kernel.

Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Zhiguang Liu <zhiguang.liu@intel.com>
Cc: Dandan Bi <dandan.bi@intel.com>
Signed-off-by: Dhaval Sharma <dhaval@rivosinc.com>
Acked-by: Chasel Chiu <chasel.chiu@...>
---

Notes:
    v4:
    - Fix typos and commit message adding more clarity to patch subject
    v3:
    - Added description of ACPI spec clarification based on which this patch is created
    - Optimizing if-else flow
    v2:
    - Added proper indentation for else if

 MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiTableProtocol.c | 23 ++++++++++++++------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiTableProtocol.c b/MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiTableProtocol.c
index e09bc9b704f5..61af6047a2a7 100644
--- a/MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiTableProtocol.c
+++ b/MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiTableProtocol.c
@@ -1892,14 +1892,23 @@ InstallAcpiTableFromHob (
           }
         }
 
-        if (((EFI_ACPI_3_0_FIXED_ACPI_DESCRIPTION_TABLE *)ChildTable)->Dsdt != 0) {
+        //
+        // First check if xDSDT is available, as that is preferred as per
+        // ACPI Spec 6.5+ Table 5-9 X_DSDT definition
+        //
+        if (((EFI_ACPI_3_0_FIXED_ACPI_DESCRIPTION_TABLE *)ChildTable)->XDsdt != 0) {
+          TableToInstall = (VOID *)(UINTN)((EFI_ACPI_3_0_FIXED_ACPI_DESCRIPTION_TABLE *)ChildTable)->XDsdt;
+        } else if (((EFI_ACPI_3_0_FIXED_ACPI_DESCRIPTION_TABLE *)ChildTable)->Dsdt != 0) {
           TableToInstall = (VOID *)(UINTN)((EFI_ACPI_3_0_FIXED_ACPI_DESCRIPTION_TABLE *)ChildTable)->Dsdt;
-          Status         = AddTableToList (AcpiTableInstance, TableToInstall, TRUE, Version, TRUE, &TableKey);
-          if (EFI_ERROR (Status)) {
-            DEBUG ((DEBUG_ERROR, "InstallAcpiTableFromHob: Fail to add ACPI table DSDT\n"));
-            ASSERT_EFI_ERROR (Status);
-            break;
-          }
+        } else {
+          break;
+        }
+
+        Status = AddTableToList (AcpiTableInstance, TableToInstall, TRUE, Version, TRUE, &TableKey);
+        if (EFI_ERROR (Status)) {
+          DEBUG ((DEBUG_ERROR, "InstallAcpiTableFromHob: Fail to add ACPI table DSDT\n"));
+          ASSERT_EFI_ERROR (Status);
+          break;
         }
       }
     }
-- 
2.39.2



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