reset: Add RESET_TYPE_WAKEUP

Some devices need to distinguish cold start reset from waking up from a
suspended state. This patch adds new value to the enum, and updates the
i386 wakeup method to use this new reset type.

Message-ID: <20240904103722.946194-3-jmarcin@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Juraj Marcin <jmarcin@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>

docs/devel/reset.rst

@@ -44,6 +44,17 @@ The Resettable interface handles reset types with an enum ``ResetType``:
   value on each cold reset, such as RNG seed information, and which they
   must not reinitialize on a snapshot-load reset.
 
+``RESET_TYPE_WAKEUP``
+  If the machine supports waking up from a suspended state and needs to reset
+  its devices during wake-up (from the ``MachineClass::wakeup()`` method), this
+  reset type should be used for such a request. Devices can utilize this reset
+  type to differentiate the reset requested during machine wake-up from other
+  reset requests. For example, RAM content must not be lost during wake-up, and
+  memory devices like virtio-mem that provide additional RAM must not reset
+  such state during wake-ups, but might do so during cold resets. However, this
+  reset type should not be used for wake-up detection, as not every machine
+  type issues a device reset request during wake-up.
+
 ``RESET_TYPE_S390_CPU_NORMAL``
   This is only used for S390 CPU objects; it clears interrupts, stops
   processing, and clears the TLB, but does not touch register contents.
@@ -53,7 +64,6 @@ The Resettable interface handles reset types with an enum ``ResetType``:
   ``RESET_TYPE_S390_CPU_NORMAL`` does and also clears the PSW, prefix,
   FPC, timer and control registers. It does not touch gprs, fprs or acrs.
 
-
 Devices which implement reset methods must treat any unknown ``ResetType``
 as equivalent to ``RESET_TYPE_COLD``; this will reduce the amount of
 existing code we need to change if we add more types in future.

hw/i386/pc.c

@@ -1732,7 +1732,7 @@ static void pc_machine_reset(MachineState *machine, ResetType type)
 static void pc_machine_wakeup(MachineState *machine)
 {
     cpu_synchronize_all_states();
-    pc_machine_reset(machine, RESET_TYPE_COLD);
+    pc_machine_reset(machine, RESET_TYPE_WAKEUP);
     cpu_synchronize_all_post_reset();
 }
 

include/hw/resettable.h

@@ -29,6 +29,7 @@ typedef struct ResettableState ResettableState;
  * Types of reset.
  *
  * + Cold: reset resulting from a power cycle of the object.
+ * + Wakeup: reset resulting from a wake-up from a suspended state.
  *
  * TODO: Support has to be added to handle more types. In particular,
  * ResettableState structure needs to be expanded.
@@ -36,6 +37,7 @@ typedef struct ResettableState ResettableState;
 typedef enum ResetType {
     RESET_TYPE_COLD,
     RESET_TYPE_SNAPSHOT_LOAD,
+    RESET_TYPE_WAKEUP,
     RESET_TYPE_S390_CPU_INITIAL,
     RESET_TYPE_S390_CPU_NORMAL,
 } ResetType;