Ping On Tue, Sep 27, 2022 at 11:46:53AM -0400, Peter Xu wrote: > It's possible that we want to reap a dirty ring on a vcpu that is during > creation, because the vcpu is put onto list (CPU_FOREACH visible) before > initialization of the structures. In this case: > > qemu_init_vcpu > x86_cpu_realizefn > cpu_exec_realizefn > cpu_list_add <---- can be probed by CPU_FOREACH > qemu_init_vcpu > cpus_accel->create_vcpu_thread(cpu); > kvm_init_vcpu > map kvm_dirty_gfns <--- kvm_dirty_gfns valid > > Don't try to reap dirty ring on vcpus during creation or it'll crash. > > Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2124756 > Reported-by: Xiaohui Li <xiao...@redhat.com> > Signed-off-by: Peter Xu <pet...@redhat.com> > --- > 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 5acab1767f..df5fabd3a8 100644 > --- a/accel/kvm/kvm-all.c > +++ b/accel/kvm/kvm-all.c > @@ -757,6 +757,15 @@ static uint32_t kvm_dirty_ring_reap_one(KVMState *s, > CPUState *cpu) > uint32_t ring_size = s->kvm_dirty_ring_size; > uint32_t count = 0, fetch = cpu->kvm_fetch_index; > > + /* > + * It's possible that we race with vcpu creation code where the vcpu is > + * put onto the vcpus list but not yet initialized the dirty ring > + * structures. If so, skip it. > + */ > + if (!cpu->created) { > + return 0; > + } > + > assert(dirty_gfns && ring_size); > trace_kvm_dirty_ring_reap_vcpu(cpu->cpu_index); > > -- > 2.37.3 >
-- Peter Xu
