reset: allow registering handlers that aren't called by snapshot loading

Snapshot loading only expects to call deterministic handlers, not
non-deterministic ones. So introduce a way of registering handlers that
won't be called when reseting for snapshots.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Message-id: 20221025004327.568476-2-Jason@zx2c4.com
[PMM: updated json doc comment with Markus' text; fixed
 checkpatch style nit]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/arm/aspeed.c

@@ -1356,12 +1356,12 @@ static void aspeed_machine_bletchley_class_init(ObjectClass *oc, void *data)
         aspeed_soc_num_cpus(amc->soc_name);
 }
 
-static void fby35_reset(MachineState *state)
+static void fby35_reset(MachineState *state, ShutdownCause reason)
 {
     AspeedMachineState *bmc = ASPEED_MACHINE(state);
     AspeedGPIOState *gpio = &bmc->soc.gpio;
 
-    qemu_devices_reset();
+    qemu_devices_reset(reason);
 
     /* Board ID: 7 (Class-1, 4 slots) */
     object_property_set_bool(OBJECT(gpio), "gpioV4", true, &error_fatal);

hw/arm/mps2-tz.c

@@ -1239,7 +1239,7 @@ static void mps2_set_remap(Object *obj, const char *value, Error **errp)
     }
 }
 
-static void mps2_machine_reset(MachineState *machine)
+static void mps2_machine_reset(MachineState *machine, ShutdownCause reason)
 {
     MPS2TZMachineState *mms = MPS2TZ_MACHINE(machine);
 
@@ -1249,7 +1249,7 @@ static void mps2_machine_reset(MachineState *machine)
      * reset see the correct mapping.
      */
     remap_memory(mms, mms->remap);
-    qemu_devices_reset();
+    qemu_devices_reset(reason);
 }
 
 static void mps2tz_class_init(ObjectClass *oc, void *data)

hw/core/reset.c

@@ -33,6 +33,7 @@ typedef struct QEMUResetEntry {
     QTAILQ_ENTRY(QEMUResetEntry) entry;
     QEMUResetHandler *func;
     void *opaque;
+    bool skip_on_snapshot_load;
 } QEMUResetEntry;
 
 static QTAILQ_HEAD(, QEMUResetEntry) reset_handlers =
@@ -47,6 +48,16 @@ void qemu_register_reset(QEMUResetHandler *func, void *opaque)
     QTAILQ_INSERT_TAIL(&reset_handlers, re, entry);
 }
 
+void qemu_register_reset_nosnapshotload(QEMUResetHandler *func, void *opaque)
+{
+    QEMUResetEntry *re = g_new0(QEMUResetEntry, 1);
+
+    re->func = func;
+    re->opaque = opaque;
+    re->skip_on_snapshot_load = true;
+    QTAILQ_INSERT_TAIL(&reset_handlers, re, entry);
+}
+
 void qemu_unregister_reset(QEMUResetHandler *func, void *opaque)
 {
     QEMUResetEntry *re;
@@ -60,12 +71,16 @@ void qemu_unregister_reset(QEMUResetHandler *func, void *opaque)
     }
 }
 
-void qemu_devices_reset(void)
+void qemu_devices_reset(ShutdownCause reason)
 {
     QEMUResetEntry *re, *nre;
 
     /* reset all devices */
     QTAILQ_FOREACH_SAFE(re, &reset_handlers, entry, nre) {
+        if (reason == SHUTDOWN_CAUSE_SNAPSHOT_LOAD &&
+            re->skip_on_snapshot_load) {
+            continue;
+        }
         re->func(re->opaque);
     }
 }

hw/hppa/machine.c

@@ -411,12 +411,12 @@ static void machine_hppa_init(MachineState *machine)
     cpu[0]->env.gr[19] = FW_CFG_IO_BASE;
 }
 
-static void hppa_machine_reset(MachineState *ms)
+static void hppa_machine_reset(MachineState *ms, ShutdownCause reason)
 {
     unsigned int smp_cpus = ms->smp.cpus;
     int i;
 
-    qemu_devices_reset();
+    qemu_devices_reset(reason);
 
     /* Start all CPUs at the firmware entry point.
      *  Monarch CPU will initialize firmware, secondary CPUs

hw/i386/microvm.c

@@ -467,7 +467,7 @@ static void microvm_machine_state_init(MachineState *machine)
     microvm_devices_init(mms);
 }
 
-static void microvm_machine_reset(MachineState *machine)
+static void microvm_machine_reset(MachineState *machine, ShutdownCause reason)
 {
     MicrovmMachineState *mms = MICROVM_MACHINE(machine);
     CPUState *cs;
@@ -480,7 +480,7 @@ static void microvm_machine_reset(MachineState *machine)
         mms->kernel_cmdline_fixed = true;
     }
 
-    qemu_devices_reset();
+    qemu_devices_reset(reason);
 
     CPU_FOREACH(cs) {
         cpu = X86_CPU(cs);

hw/i386/pc.c

@@ -1847,12 +1847,12 @@ static void pc_machine_initfn(Object *obj)
     cxl_machine_init(obj, &pcms->cxl_devices_state);
 }
 
-static void pc_machine_reset(MachineState *machine)
+static void pc_machine_reset(MachineState *machine, ShutdownCause reason)
 {
     CPUState *cs;
     X86CPU *cpu;
 
-    qemu_devices_reset();
+    qemu_devices_reset(reason);
 
     /* Reset APIC after devices have been reset to cancel
      * any changes that qemu_devices_reset() might have done.
@@ -1867,7 +1867,7 @@ static void pc_machine_reset(MachineState *machine)
 static void pc_machine_wakeup(MachineState *machine)
 {
     cpu_synchronize_all_states();
-    pc_machine_reset(machine);
+    pc_machine_reset(machine, SHUTDOWN_CAUSE_NONE);
     cpu_synchronize_all_post_reset();
 }
 

hw/ppc/pegasos2.c

@@ -248,14 +248,14 @@ static void pegasos2_pci_config_write(Pegasos2MachineState *pm, int bus,
     pegasos2_mv_reg_write(pm, pcicfg + 4, len, val);
 }
 
-static void pegasos2_machine_reset(MachineState *machine)
+static void pegasos2_machine_reset(MachineState *machine, ShutdownCause reason)
 {
     Pegasos2MachineState *pm = PEGASOS2_MACHINE(machine);
     void *fdt;
     uint64_t d[2];
     int sz;
 
-    qemu_devices_reset();
+    qemu_devices_reset(reason);
     if (!pm->vof) {
         return; /* Firmware should set up machine so nothing to do */
     }

hw/ppc/pnv.c

@@ -643,13 +643,13 @@ static void pnv_powerdown_notify(Notifier *n, void *opaque)
     }
 }
 
-static void pnv_reset(MachineState *machine)
+static void pnv_reset(MachineState *machine, ShutdownCause reason)
 {
     PnvMachineState *pnv = PNV_MACHINE(machine);
     IPMIBmc *bmc;
     void *fdt;
 
-    qemu_devices_reset();
+    qemu_devices_reset(reason);
 
     /*
      * The machine should provide by default an internal BMC simulator.

hw/ppc/spapr.c

@@ -1623,7 +1623,7 @@ void spapr_check_mmu_mode(bool guest_radix)
     }
 }
 
-static void spapr_machine_reset(MachineState *machine)
+static void spapr_machine_reset(MachineState *machine, ShutdownCause reason)
 {
     SpaprMachineState *spapr = SPAPR_MACHINE(machine);
     PowerPCCPU *first_ppc_cpu;
@@ -1649,7 +1649,7 @@ static void spapr_machine_reset(MachineState *machine)
         spapr_setup_hpt(spapr);
     }
 
-    qemu_devices_reset();
+    qemu_devices_reset(reason);
 
     spapr_ovec_cleanup(spapr->ov5_cas);
     spapr->ov5_cas = spapr_ovec_new();

hw/s390x/s390-virtio-ccw.c

@@ -411,7 +411,7 @@ static void s390_pv_prepare_reset(S390CcwMachineState *ms)
     s390_pv_prep_reset();
 }
 
-static void s390_machine_reset(MachineState *machine)
+static void s390_machine_reset(MachineState *machine, ShutdownCause reason)
 {
     S390CcwMachineState *ms = S390_CCW_MACHINE(machine);
     enum s390_reset reset_type;
@@ -433,7 +433,7 @@ static void s390_machine_reset(MachineState *machine)
             s390_machine_unprotect(ms);
         }
 
-        qemu_devices_reset();
+        qemu_devices_reset(reason);
         s390_crypto_reset();
 
         /* configure and start the ipl CPU only */

include/hw/boards.h

@@ -231,7 +231,7 @@ struct MachineClass {
     const char *deprecation_reason;
 
     void (*init)(MachineState *state);
-    void (*reset)(MachineState *state);
+    void (*reset)(MachineState *state, ShutdownCause reason);
     void (*wakeup)(MachineState *state);
     int (*kvm_type)(MachineState *machine, const char *arg);
 

include/sysemu/reset.h

@@ -1,10 +1,13 @@
 #ifndef QEMU_SYSEMU_RESET_H
 #define QEMU_SYSEMU_RESET_H
 
+#include "qapi/qapi-events-run-state.h"
+
 typedef void QEMUResetHandler(void *opaque);
 
 void qemu_register_reset(QEMUResetHandler *func, void *opaque);
+void qemu_register_reset_nosnapshotload(QEMUResetHandler *func, void *opaque);
 void qemu_unregister_reset(QEMUResetHandler *func, void *opaque);
-void qemu_devices_reset(void);
+void qemu_devices_reset(ShutdownCause reason);
 
 #endif

migration/savevm.c

@@ -3058,7 +3058,7 @@ bool load_snapshot(const char *name, const char *vmstate,
         goto err_drain;
     }
 
-    qemu_system_reset(SHUTDOWN_CAUSE_NONE);
+    qemu_system_reset(SHUTDOWN_CAUSE_SNAPSHOT_LOAD);
     mis->from_src_file = f;
 
     if (!yank_register_instance(MIGRATION_YANK_INSTANCE, errp)) {

qapi/run-state.json

@@ -86,12 +86,16 @@
 #                   ignores --no-reboot. This is useful for sanitizing
 #                   hypercalls on s390 that are used during kexec/kdump/boot
 #
+# @snapshot-load: A snapshot is being loaded by the record & replay
+#                 subsystem. This value is used only within QEMU.  It
+#                 doesn't occur in QMP. (since 7.2)
+#
 ##
 { 'enum': 'ShutdownCause',
   # Beware, shutdown_caused_by_guest() depends on enumeration order
   'data': [ 'none', 'host-error', 'host-qmp-quit', 'host-qmp-system-reset',
             'host-signal', 'host-ui', 'guest-shutdown', 'guest-reset',
-            'guest-panic', 'subsystem-reset'] }
+            'guest-panic', 'subsystem-reset', 'snapshot-load'] }
 
 ##
 # @StatusInfo:

softmmu/runstate.c

@@ -441,11 +441,16 @@ void qemu_system_reset(ShutdownCause reason)
     cpu_synchronize_all_states();
 
     if (mc && mc->reset) {
-        mc->reset(current_machine);
+        mc->reset(current_machine, reason);
     } else {
-        qemu_devices_reset();
+        qemu_devices_reset(reason);
     }
-    if (reason && reason != SHUTDOWN_CAUSE_SUBSYSTEM_RESET) {
+    switch (reason) {
+    case SHUTDOWN_CAUSE_NONE:
+    case SHUTDOWN_CAUSE_SUBSYSTEM_RESET:
+    case SHUTDOWN_CAUSE_SNAPSHOT_LOAD:
+        break;
+    default:
         qapi_event_send_reset(shutdown_caused_by_guest(reason), reason);
     }
     cpu_synchronize_all_post_reset();