Sorry, this patch is wrong. kvm_dirty_ring_reap_locked holds slots_lock, which may result in deadlock at the moment when modifying memory_region.
I am finding a better way to get known the finishing of all vcpus' creations before waking reaper up. > -----原始邮件-----发件人:"Weinan Liu" <[email protected]>发送时间:2023-02-05 00:08:08 > (星期日)收件人:[email protected]抄送:[email protected], [email protected], > "Weinan Liu" <[email protected]>主题:[PATCH] KVM: dirty ring: check if vcpu > is created before dirty_ring_reap_one > > From: Weinan Liu <[email protected]> > > Failed to assert '(dirty_gfns && ring_size)' in kvm_dirty_ring_reap_one if > the vcpu has not been finished to create yet. This bug occasionally occurs > when I open 200+ qemu instances on my 16G 6-cores x86 machine. And it must > be triggered if inserting a 'sleep(10)' into kvm_vcpu_thread_fn as below-- > > static void *kvm_vcpu_thread_fn(void *arg) > { > CPUState *cpu = arg; > int r; > > rcu_register_thread(); > > + sleep(10); > qemu_mutex_lock_iothread(); > qemu_thread_get_self(cpu->thread); > cpu->thread_id = qemu_get_thread_id(); > cpu->can_do_io = 1; > > where dirty ring reaper will wakeup but then a vcpu has not been finished > to create. > > Signed-off-by: Weinan Liu <[email protected]> > --- > accel/kvm/kvm-all.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c > index 7e6a6076b1..840da7630e 100644 > --- a/accel/kvm/kvm-all.c > +++ b/accel/kvm/kvm-all.c > @@ -719,6 +719,15 @@ static uint64_t kvm_dirty_ring_reap_locked(KVMState *s, > CPUState* cpu) > total = kvm_dirty_ring_reap_one(s, cpu); > } else { > CPU_FOREACH(cpu) { > + /* > + * Must ensure kvm_init_vcpu is finished, so cpu->kvm_dirty_gfns > is > + * available. > + */ > + while (cpu->created == false) { > + qemu_mutex_unlock_iothread(); > + qemu_mutex_lock_iothread(); > + } > + > total += kvm_dirty_ring_reap_one(s, cpu); > } > } > -- > 2.25.1 ------------------------------ Weinan Liu （刘炜楠） Department of Computer Science and Technology School of Informatics Xiamen University
