[PATCH v2 7/9] i386: acpi: Don't build HPET ACPI entry if HPET is disabled

[isaku . yamahata]

From: Sean Christopherson <sean.j.christopherson@intel.com>

Omit HPET AML if the HPET is disabled, QEMU is not emulating it and the
guest may get confused by seeing HPET in the ACPI tables without a
"physical" device present.

The change of DSDT when -no-hpet is as follows.

@@ -141,47 +141,6 @@ DefinitionBlock ("", "DSDT", 1, "BOCHS "
         }
     }

-    Scope (_SB)
-    {
-        Device (HPET)
-        {
-            Name (_HID, EisaId ("PNP0103") /* HPET System Timer */)  // _HID: 
Hardware ID
-            Name (_UID, Zero)  // _UID: Unique ID
-            OperationRegion (HPTM, SystemMemory, 0xFED00000, 0x0400)
-            Field (HPTM, DWordAcc, Lock, Preserve)
-            {
-                VEND,   32,
-                PRD,    32
-            }
-
-            Method (_STA, 0, NotSerialized)  // _STA: Status
-            {
-                Local0 = VEND /* \_SB_.HPET.VEND */
-                Local1 = PRD /* \_SB_.HPET.PRD_ */
-                Local0 >>= 0x10
-                If (((Local0 == Zero) || (Local0 == 0xFFFF)))
-                {
-                    Return (Zero)
-                }
-
-                If (((Local1 == Zero) || (Local1 > 0x05F5E100)))
-                {
-                    Return (Zero)
-                }
-
-                Return (0x0F)
-            }
-
-            Name (_CRS, ResourceTemplate ()  // _CRS: Current Resource Settings
-            {
-                Memory32Fixed (ReadOnly,
-                    0xFED00000,         // Address Base
-                    0x00000400,         // Address Length
-                    )
-            })
-        }
-    }
-
     Scope (_SB.PCI0)
     {
         Device (ISA)

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 hw/i386/acpi-build.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index bcb1f65c1d..73ec0b6d32 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -1405,7 +1405,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
         aml_append(sb_scope, dev);
         aml_append(dsdt, sb_scope);
 
-        build_hpet_aml(dsdt);
+        if (misc->has_hpet) {
+            build_hpet_aml(dsdt);
+        }
         build_piix4_isa_bridge(dsdt);
         build_isa_devices_aml(dsdt);
         if (pm->pcihp_bridge_en || pm->pcihp_root_en) {
@@ -1450,7 +1452,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
 
         aml_append(dsdt, sb_scope);
 
-        build_hpet_aml(dsdt);
+        if (misc->has_hpet) {
+            build_hpet_aml(dsdt);
+        }
         build_q35_isa_bridge(dsdt);
         build_isa_devices_aml(dsdt);
         build_q35_pci0_int(dsdt);
-- 
2.17.1