Tables: Add AcpiUninstallTable() to remove ACPI tables

There are existing internal functions that allow the removal of ACPI
tables, but they are not exposed to OS in any useful way.

Introduce AcpiUninstallTable() which allows table states to be
"UNINSTALLED" in the global table list, resulting in failures of subsequent
calls to AcpiGetTable() for those tables.

The rationale for this change is the ability to remove the BGRT table
during kexec boot. The BGRT table refers to memory regions that are no
longer reserved by the firmware once the kexec kernel boots, having been
released for general allocation by the previous kernel.

Note that AcpiTbUninstallTable() is designed with limitation that it must
only be called after an AcpiTbInstallTable() call as it doesn't handle
table reference count synchronizations. So it is only safe in a
single-threaded early booting environment.

Original-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>

source/components/tables/tbxfload.c

@@ -369,6 +369,7 @@ AcpiTbLoadNamespace (
  * PARAMETERS:  Address             - Address of the ACPI table to be installed.
  *              Physical            - Whether the address is a physical table
  *                                    address or not
+ *              OutIndex            - Where the table index is returned
  *
  * RETURN:      Status
  *
@@ -381,11 +382,11 @@ AcpiTbLoadNamespace (
 ACPI_STATUS
 AcpiInstallTable (
     ACPI_PHYSICAL_ADDRESS   Address,
-    BOOLEAN                 Physical)
+    BOOLEAN                 Physical,
+    UINT32                  *OutIndex)
 {
     ACPI_STATUS             Status;
     UINT8                   Flags;
-    UINT32                  TableIndex;
 
 
     ACPI_FUNCTION_TRACE (AcpiInstallTable);
@@ -401,14 +402,51 @@ AcpiInstallTable (
     }
 
     Status = AcpiTbVerifyAndInstallTable (Address, Flags,
-        FALSE, FALSE, &TableIndex);
+        FALSE, FALSE, OutIndex);
 
     return_ACPI_STATUS (Status);
 }
 
 ACPI_EXPORT_SYMBOL_INIT (AcpiInstallTable)
 
 
+/*******************************************************************************
+ *
+ * FUNCTION:    AcpiUninstallTable
+ *
+ * PARAMETERS:  TableIndex          - Table index
+ *
+ * RETURN:      None
+ *
+ * DESCRIPTION: Dynamically uninstall an ACPI table.
+ *              Note: This function should only be invoked after
+ *                    AcpiInitializeTables() and before AcpiLoadTables().
+ *
+ ******************************************************************************/
+
+void
+AcpiUninstallTable (
+    UINT32                  TableIndex)
+{
+
+    ACPI_FUNCTION_TRACE (AcpiUninstallTable);
+
+
+    /*
+     * This function can only be used during early stage, so the table mutex
+     * isn't required to be held.
+     */
+    if (TableIndex < AcpiGbl_RootTableList.CurrentTableCount)
+    {
+        AcpiTbUninstallTable (&AcpiGbl_RootTableList.Tables[TableIndex]);
+    }
+
+    return_VOID;
+}
+
+ACPI_EXPORT_SYMBOL_INIT (AcpiUninstallTable)
+
+
 /*******************************************************************************
  *
  * FUNCTION:    AcpiLoadTable

source/include/acpixf.h

@@ -595,7 +595,13 @@ ACPI_EXTERNAL_RETURN_STATUS (
 ACPI_STATUS
 AcpiInstallTable (
     ACPI_PHYSICAL_ADDRESS   Address,
-    BOOLEAN                 Physical))
+    BOOLEAN                 Physical,
+    UINT32                  *OutIndex))
+
+ACPI_EXTERNAL_RETURN_VOID (
+void
+AcpiUninstallTable (
+    UINT32                  TableIndex))
 
 ACPI_EXTERNAL_RETURN_STATUS (
 ACPI_STATUS