When we stop a VM for more than 30 seconds and then resume it, by qemu
monitor command "stop" and "cont", Linux on VM will complain of "soft
lockup - CPU#x stuck for xxs!" as below:
[ 2783.809517] watchdog: BUG: soft lockup - CPU#3 stuck for 2395s!
[ 2783.809559] watchdog: BUG: soft lockup - CPU#2 stuck for 2395s!
[ 2783.809561] watchdog: BUG: soft lockup - CPU#1 stuck for 2395s!
[ 2783.809563] Modules linked in...
This is because Guest Linux uses generic timer virtual counter as
a software watchdog, and CNTVCT_EL0 does not stop when VM is stopped
by qemu.
This patch is to fix this issue by saving the value of CNTVCT_EL0 when
stopping and restoring it when resuming.
Cc: Peter Maydell <peter.mayd...@linaro.org>
Signed-off-by: Heyi Guo <guoh...@huawei.com>
---
target/arm/cpu.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 65 insertions(+)
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 96f0ff0..7bbba3d 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -896,6 +896,60 @@ static void arm_cpu_finalizefn(Object *obj)
#endif
}
+static int get_vcpu_timer_tick(CPUState *cs, uint64_t *tick_at_pause)
+{
+ int err;
+ struct kvm_one_reg reg;
+
+ reg.id = KVM_REG_ARM_TIMER_CNT;
+ reg.addr = (uintptr_t) tick_at_pause;
+
+ err = kvm_vcpu_ioctl(cs, KVM_GET_ONE_REG, ®);
+ return err;
+}
+
+static int set_vcpu_timer_tick(CPUState *cs, uint64_t tick_at_pause)
+{
+ int err;
+ struct kvm_one_reg reg;
+
+ reg.id = KVM_REG_ARM_TIMER_CNT;
+ reg.addr = (uintptr_t) &tick_at_pause;
+
+ err = kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, ®);
+ return err;
+}
+
+static void arch_timer_change_state_handler(void *opaque, int running,
+ RunState state)
+{
+ static uint64_t hw_ticks_at_paused;
+ static RunState pre_state = RUN_STATE__MAX;
+ int err;
+ CPUState *cs = (CPUState *)opaque;
+
+ switch (state) {
+ case RUN_STATE_PAUSED:
+ err = get_vcpu_timer_tick(cs, &hw_ticks_at_paused);
+ if (err) {
+ error_report("Get vcpu timer tick failed: %d", err);
+ }
+ break;
+ case RUN_STATE_RUNNING:
+ if (pre_state == RUN_STATE_PAUSED) {
+ err = set_vcpu_timer_tick(cs, hw_ticks_at_paused);
+ if (err) {
+ error_report("Resume vcpu timer tick failed: %d", err);
+ }
+ }
+ break;
+ default:
+ break;
+ }
+
+ pre_state = state;
+}
+
static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
{
CPUState *cs = CPU(dev);
@@ -906,6 +960,12 @@ static void arm_cpu_realizefn(DeviceState *dev, Error
**errp)
Error *local_err = NULL;
bool no_aa32 = false;
+ /*
+ * Only add change state handler for arch timer once, for KVM will help to
+ * synchronize virtual timer of all VCPUs.
+ */
+ static bool arch_timer_change_state_handler_added;
+
/* If we needed to query the host kernel for the CPU features
* then it's possible that might have failed in the initfn, but
* this is the first point where we can report it.
@@ -1181,6 +1241,11 @@ static void arm_cpu_realizefn(DeviceState *dev, Error
**errp)
init_cpreg_list(cpu);
+ if (!arch_timer_change_state_handler_added && kvm_enabled()) {
+ qemu_add_vm_change_state_handler(arch_timer_change_state_handler, cs);
+ arch_timer_change_state_handler_added = true;
+ }
+
#ifndef CONFIG_USER_ONLY
if (cpu->has_el3 || arm_feature(env, ARM_FEATURE_M_SECURITY)) {
cs->num_ases = 2;
--
1.8.3.1
