gdbstub: move sstep flags probing into AccelClass

The support of single-stepping is very much dependent on support from
the accelerator we are using. To avoid special casing in gdbstub move
the probing out to an AccelClass function so future accelerators can
put their code there.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Mads Ynddal <mads@ynddal.dk>
Message-Id: <20220929114231.583801-44-alex.bennee@linaro.org>

3 files changed, 40 insertions, 1 deletions

diff --git a/accel/accel-common.c b/accel/accel-common.c
index 50035bda55..df72cc989a 100644
--- a/accel/accel-common.c
+++ b/accel/accel-common.c
@@ -129,6 +129,16 @@ bool accel_cpu_realizefn(CPUState *cpu, Error **errp)
     return true;
 }
 
+int accel_supported_gdbstub_sstep_flags(void)
+{
+    AccelState *accel = current_accel();
+    AccelClass *acc = ACCEL_GET_CLASS(accel);
+    if (acc->gdbstub_supported_sstep_flags) {
+        return acc->gdbstub_supported_sstep_flags();
+    }
+    return 0;
+}
+
 static const TypeInfo accel_cpu_type = {
     .name = TYPE_ACCEL_CPU,
     .parent = TYPE_OBJECT,
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 5acab1767f..c55938453a 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -175,7 +175,7 @@ bool kvm_direct_msi_allowed;
 bool kvm_ioeventfd_any_length_allowed;
 bool kvm_msi_use_devid;
 bool kvm_has_guest_debug;
-int kvm_sstep_flags;
+static int kvm_sstep_flags;
 static bool kvm_immediate_exit;
 static hwaddr kvm_max_slot_size = ~0;
 
@@ -3712,6 +3712,17 @@ static void kvm_accel_instance_init(Object *obj)
     s->kvm_dirty_ring_size = 0;
 }
 
+/**
+ * kvm_gdbstub_sstep_flags():
+ *
+ * Returns: SSTEP_* flags that KVM supports for guest debug. The
+ * support is probed during kvm_init()
+ */
+static int kvm_gdbstub_sstep_flags(void)
+{
+    return kvm_sstep_flags;
+}
+
 static void kvm_accel_class_init(ObjectClass *oc, void *data)
 {
     AccelClass *ac = ACCEL_CLASS(oc);
@@ -3719,6 +3730,7 @@ static void kvm_accel_class_init(ObjectClass *oc, void *data)
     ac->init_machine = kvm_init;
     ac->has_memory = kvm_accel_has_memory;
     ac->allowed = &kvm_allowed;
+    ac->gdbstub_supported_sstep_flags = kvm_gdbstub_sstep_flags;
 
     object_class_property_add(oc, "kernel-irqchip", "on|off|split",
         NULL, kvm_set_kernel_irqchip,
diff --git a/accel/tcg/tcg-all.c b/accel/tcg/tcg-all.c
index 47952eecd7..30b503fb22 100644
--- a/accel/tcg/tcg-all.c
+++ b/accel/tcg/tcg-all.c
@@ -25,6 +25,7 @@
 
 #include "qemu/osdep.h"
 #include "sysemu/tcg.h"
+#include "sysemu/replay.h"
 #include "sysemu/cpu-timers.h"
 #include "tcg/tcg.h"
 #include "qapi/error.h"
@@ -207,12 +208,28 @@ static void tcg_set_splitwx(Object *obj, bool value, Error **errp)
     s->splitwx_enabled = value;
 }
 
+static int tcg_gdbstub_supported_sstep_flags(void)
+{
+    /*
+     * In replay mode all events will come from the log and can't be
+     * suppressed otherwise we would break determinism. However as those
+     * events are tied to the number of executed instructions we won't see
+     * them occurring every time we single step.
+     */
+    if (replay_mode != REPLAY_MODE_NONE) {
+        return SSTEP_ENABLE;
+    } else {
+        return SSTEP_ENABLE | SSTEP_NOIRQ | SSTEP_NOTIMER;
+    }
+}
+
 static void tcg_accel_class_init(ObjectClass *oc, void *data)
 {
     AccelClass *ac = ACCEL_CLASS(oc);
     ac->name = "tcg";
     ac->init_machine = tcg_init_machine;
     ac->allowed = &tcg_allowed;
+    ac->gdbstub_supported_sstep_flags = tcg_gdbstub_supported_sstep_flags;
 
     object_class_property_add_str(oc, "thread",
                                   tcg_get_thread,