2.1-rc2 behaves exactly the same.
Interestingly enough, reseting guest system causes I/O to work again. So
it's not qemu that hangs on IO, rather it fails to notify guest about
completed operations that were issued during migration.
And its somehow caused by calling cpu_synchronize_all_states() inside
kvmclock_vm_state_change().
As for testing with cache=writeback, I'll try to setup some iscsi to test
it.
Awesome, thanks! AFAIK you`ll not be able to use write cache with
iscsi for migration. VM which had a reset before hangs always when
freshly launched have a chance to be migrated successfully. And yes,
it looks like lower layer forgetting to notify driver about some
operations at a glance.
Andrey,
could you try attached patch? It's an incredibly ugly workaround that
calls cpu_synchronize_all_states() in a way that bypasses lazy execution
logic.
But it works for me. If that works for you as well, its somehow related
to lazy execution of cpu_synchronize_all_states.
--
mg
diff -ru qemu-2.1.0-rc2/cpus.c qemu-2.1.0-rc2-fixed/cpus.c
--- qemu-2.1.0-rc2/cpus.c 2014-07-15 23:49:14.000000000 +0200
+++ qemu-2.1.0-rc2-fixed/cpus.c 2014-07-17 15:09:09.306696284 +0200
@@ -505,6 +505,15 @@
}
}
+void cpu_synchronize_all_states_always(void)
+{
+ CPUState *cpu;
+
+ CPU_FOREACH(cpu) {
+ cpu_synchronize_state_always(cpu);
+ }
+}
+
void cpu_synchronize_all_post_reset(void)
{
CPUState *cpu;
diff -ru qemu-2.1.0-rc2/hw/i386/kvm/clock.c qemu-2.1.0-rc2-fixed/hw/i386/kvm/clock.c
--- qemu-2.1.0-rc2/hw/i386/kvm/clock.c 2014-07-15 23:49:14.000000000 +0200
+++ qemu-2.1.0-rc2-fixed/hw/i386/kvm/clock.c 2014-07-17 15:08:25.627063756 +0200
@@ -126,7 +126,7 @@
return;
}
- cpu_synchronize_all_states();
+ cpu_synchronize_all_states_always();
ret = kvm_vm_ioctl(kvm_state, KVM_GET_CLOCK, &data);
if (ret < 0) {
fprintf(stderr, "KVM_GET_CLOCK failed: %s\n", strerror(ret));
diff -ru qemu-2.1.0-rc2/include/sysemu/cpus.h qemu-2.1.0-rc2-fixed/include/sysemu/cpus.h
--- qemu-2.1.0-rc2/include/sysemu/cpus.h 2014-07-15 23:49:14.000000000 +0200
+++ qemu-2.1.0-rc2-fixed/include/sysemu/cpus.h 2014-07-17 15:09:23.256578916 +0200
@@ -7,6 +7,7 @@
void pause_all_vcpus(void);
void cpu_stop_current(void);
+void cpu_synchronize_all_states_always(void);
void cpu_synchronize_all_states(void);
void cpu_synchronize_all_post_reset(void);
void cpu_synchronize_all_post_init(void);
diff -ru qemu-2.1.0-rc2/include/sysemu/kvm.h qemu-2.1.0-rc2-fixed/include/sysemu/kvm.h
--- qemu-2.1.0-rc2/include/sysemu/kvm.h 2014-07-15 23:49:14.000000000 +0200
+++ qemu-2.1.0-rc2-fixed/include/sysemu/kvm.h 2014-07-17 15:11:54.855303171 +0200
@@ -346,9 +346,11 @@
#endif /* NEED_CPU_H */
void kvm_cpu_synchronize_state(CPUState *cpu);
+void kvm_cpu_synchronize_state_always(CPUState *cpu);
void kvm_cpu_synchronize_post_reset(CPUState *cpu);
void kvm_cpu_synchronize_post_init(CPUState *cpu);
+
/* generic hooks - to be moved/refactored once there are more users */
static inline void cpu_synchronize_state(CPUState *cpu)
@@ -358,6 +360,13 @@
}
}
+static inline void cpu_synchronize_state_always(CPUState *cpu)
+{
+ if (kvm_enabled()) {
+ kvm_cpu_synchronize_state_always(cpu);
+ }
+}
+
static inline void cpu_synchronize_post_reset(CPUState *cpu)
{
if (kvm_enabled()) {
diff -ru qemu-2.1.0-rc2/kvm-all.c qemu-2.1.0-rc2-fixed/kvm-all.c
--- qemu-2.1.0-rc2/kvm-all.c 2014-07-15 23:49:14.000000000 +0200
+++ qemu-2.1.0-rc2-fixed/kvm-all.c 2014-07-17 15:14:04.884208826 +0200
@@ -1652,6 +1652,13 @@
s->coalesced_flush_in_progress = false;
}
+static void do_kvm_cpu_synchronize_state_always(void *arg)
+{
+ CPUState *cpu = arg;
+
+ kvm_arch_get_registers(cpu);
+}
+
static void do_kvm_cpu_synchronize_state(void *arg)
{
CPUState *cpu = arg;
@@ -1669,6 +1676,11 @@
}
}
+void kvm_cpu_synchronize_state_always(CPUState *cpu)
+{
+ run_on_cpu(cpu, do_kvm_cpu_synchronize_state_always, cpu);
+}
+
void kvm_cpu_synchronize_post_reset(CPUState *cpu)
{
kvm_arch_put_registers(cpu, KVM_PUT_RESET_STATE);
