[PATCH RFC 7/7] qemu: command: Don't format '-machine acpi=off' for machine types not supporting ACPI

[Peter Krempa]

Certain ARM machine types don't support ACPI. Given our historically
broken design of using '<acpi/>' without attribute to enable ACPI and
qemu's default of enabling it without '-no-acpi' such configurations
would not work.

Now when qemu reports whether given machine type supports ACPI we can do
a better decision and un-break those configs. Unfortunately not
retroactively.

Resolves: https://gitlab.com/libvirt/libvirt/-/issues/297
---
 src/qemu/qemu_command.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index cb21765509..7b80490b77 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -6787,6 +6787,7 @@ qemuBuildMachineACPI(virBuffer *machineOptsBuf,
                      virQEMUCaps *qemuCaps)
 {
     virTristateSwitch defACPI = def->features[VIR_DOMAIN_FEATURE_ACPI];
+    virTristateBool machineACPI = virQEMUCapsMachineSupportsACPI(qemuCaps, def->virtType, def->os.machine);

     /* QEMU_CAPS_MACHINE_ACPI indicates that '-machine acpi=' syntax should be
      * used. Presence of QEMU_CAPS_MACHINE_ACPI masks out QEMU_CAPS_NO_ACPI and
@@ -6801,9 +6802,17 @@ qemuBuildMachineACPI(virBuffer *machineOptsBuf,
      * The default in qemu was historically to enable ACPI and '-no-acpi' was
      * used to disable it when the '<acpi/>' flag is not present.
      *
-     * We thus convert VIR_TRISTATE_SWITCH_ABSENT to VIR_TRISTATE_SWITCH_OFF.
+     * VIR_TRISTATE_SWITCH_ABSENT can't be converted to VIR_TRISTATE_SWITCH_OFF
+     * blindy as there are machine types on certain platforms which do not
+     * support ACPI, but others do. Thus the presence of QEMU_CAPS_MACHINE_ACPI
+     * capability does not fully cover the above.
+     *
+     * We thus avoid conversion of VIR_TRISTATE_SWITCH_ABSENT to
+     * VIR_TRISTATE_SWITCH_OFF if we are certain that given machine does not
+     * support ACPI.
      */
-    if (defACPI == VIR_TRISTATE_SWITCH_ABSENT)
+    if (machineACPI != VIR_TRISTATE_BOOL_NO &&
+        defACPI == VIR_TRISTATE_SWITCH_ABSENT)
         defACPI = VIR_TRISTATE_SWITCH_OFF;

     if (defACPI != VIR_TRISTATE_SWITCH_ABSENT)
-- 
2.39.2