kvm: Synchronize the backup bitmap in the last stage

In the last stage of live migration or memory slot removal, the
backup bitmap needs to be synchronized when it has been enabled.

Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Tested-by: Zhenyu Zhang <zhenyzha@redhat.com>
Message-Id: <20230509022122.20888-3-gshan@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

accel/kvm/kvm-all.c

@@ -1361,6 +1361,10 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml,
                  */
                 if (kvm_state->kvm_dirty_ring_size) {
                     kvm_dirty_ring_reap_locked(kvm_state, NULL);
+                    if (kvm_state->kvm_dirty_ring_with_bitmap) {
+                        kvm_slot_sync_dirty_pages(mem);
+                        kvm_slot_get_dirty_log(kvm_state, mem);
+                    }
                 } else {
                     kvm_slot_get_dirty_log(kvm_state, mem);
                 }
@@ -1582,6 +1586,12 @@ static void kvm_log_sync_global(MemoryListener *l, bool last_stage)
         mem = &kml->slots[i];
         if (mem->memory_size && mem->flags & KVM_MEM_LOG_DIRTY_PAGES) {
             kvm_slot_sync_dirty_pages(mem);
+
+            if (s->kvm_dirty_ring_with_bitmap && last_stage &&
+                kvm_slot_get_dirty_log(s, mem)) {
+                kvm_slot_sync_dirty_pages(mem);
+            }
+
             /*
              * This is not needed by KVM_GET_DIRTY_LOG because the
              * ioctl will unconditionally overwrite the whole region.
@@ -3710,6 +3720,7 @@ static void kvm_accel_instance_init(Object *obj)
     s->kernel_irqchip_split = ON_OFF_AUTO_AUTO;
     /* KVM dirty ring is by default off */
     s->kvm_dirty_ring_size = 0;
+    s->kvm_dirty_ring_with_bitmap = false;
     s->notify_vmexit = NOTIFY_VMEXIT_OPTION_RUN;
     s->notify_window = 0;
     s->xen_version = 0;

include/sysemu/kvm_int.h

@@ -115,6 +115,7 @@ struct KVMState
     } *as;
     uint64_t kvm_dirty_ring_bytes;  /* Size of the per-vcpu dirty ring */
     uint32_t kvm_dirty_ring_size;   /* Number of dirty GFNs per ring */
+    bool kvm_dirty_ring_with_bitmap;
     struct KVMDirtyRingReaper reaper;
     NotifyVmexitOption notify_vmexit;
     uint32_t notify_window;