target-arm/powerctl: defer cpu reset work to CPU context

When switching a new vCPU on we want to complete a bunch of the setup
work before we start scheduling the vCPU thread. To do this cleanly we
defer vCPU setup to async work which will run the vCPUs execution
context as the thread is woken up. The scheduling of the work will kick
the vCPU awake.

This avoids potential races in MTTCG system emulation.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 40 insertions, 1 deletions

diff --git a/target/arm/machine.c b/target/arm/machine.c
index fa5ec76090..d8094a840b 100644
--- a/target/arm/machine.c
+++ b/target/arm/machine.c
@@ -211,6 +211,38 @@ static const VMStateInfo vmstate_cpsr = {
     .put = put_cpsr,
 };
 
+static int get_power(QEMUFile *f, void *opaque, size_t size,
+                    VMStateField *field)
+{
+    ARMCPU *cpu = opaque;
+    bool powered_off = qemu_get_byte(f);
+    cpu->power_state = powered_off ? PSCI_OFF : PSCI_ON;
+    return 0;
+}
+
+static int put_power(QEMUFile *f, void *opaque, size_t size,
+                    VMStateField *field, QJSON *vmdesc)
+{
+    ARMCPU *cpu = opaque;
+
+    /* Migration should never happen while we transition power states */
+
+    if (cpu->power_state == PSCI_ON ||
+        cpu->power_state == PSCI_OFF) {
+        bool powered_off = (cpu->power_state == PSCI_OFF) ? true : false;
+        qemu_put_byte(f, powered_off);
+        return 0;
+    } else {
+        return 1;
+    }
+}
+
+static const VMStateInfo vmstate_powered_off = {
+    .name = "powered_off",
+    .get = get_power,
+    .put = put_power,
+};
+
 static void cpu_pre_save(void *opaque)
 {
     ARMCPU *cpu = opaque;
@@ -329,7 +361,14 @@ const VMStateDescription vmstate_arm_cpu = {
         VMSTATE_UINT64(env.exception.vaddress, ARMCPU),
         VMSTATE_TIMER_PTR(gt_timer[GTIMER_PHYS], ARMCPU),
         VMSTATE_TIMER_PTR(gt_timer[GTIMER_VIRT], ARMCPU),
-        VMSTATE_BOOL(powered_off, ARMCPU),
+        {
+            .name = "power_state",
+            .version_id = 0,
+            .size = sizeof(bool),
+            .info = &vmstate_powered_off,
+            .flags = VMS_SINGLE,
+            .offset = 0,
+        },
         VMSTATE_END_OF_LIST()
     },
     .subsections = (const VMStateDescription*[]) {