diff options
Diffstat (limited to 'migration/vmstate.c')
| -rw-r--r-- | migration/vmstate.c | 151 |
1 files changed, 123 insertions, 28 deletions
diff --git a/migration/vmstate.c b/migration/vmstate.c index fa002b24e8..82bd005a83 100644 --- a/migration/vmstate.c +++ b/migration/vmstate.c @@ -51,6 +51,36 @@ vmstate_field_exists(const VMStateDescription *vmsd, const VMStateField *field, return result; } +/* + * Create a fake nullptr field when there's a NULL pointer detected in the + * array of a VMS_ARRAY_OF_POINTER VMSD field. It's needed because we + * can't dereference the NULL pointer. + */ +static const VMStateField * +vmsd_create_fake_nullptr_field(const VMStateField *field) +{ + VMStateField *fake = g_new0(VMStateField, 1); + + /* It can only happen on an array of pointers! */ + assert(field->flags & VMS_ARRAY_OF_POINTER); + + /* Some of fake's properties should match the original's */ + fake->name = field->name; + fake->version_id = field->version_id; + + /* Do not need "field_exists" check as it always exists (which is null) */ + fake->field_exists = NULL; + + /* See vmstate_info_nullptr - use 1 byte to represent nullptr */ + fake->size = 1; + fake->info = &vmstate_info_nullptr; + fake->flags = VMS_SINGLE; + + /* All the rest fields shouldn't matter.. */ + + return (const VMStateField *)fake; +} + static int vmstate_n_elems(void *opaque, const VMStateField *field) { int n_elems = 1; @@ -143,23 +173,39 @@ int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd, } for (i = 0; i < n_elems; i++) { void *curr_elem = first_elem + size * i; + const VMStateField *inner_field; if (field->flags & VMS_ARRAY_OF_POINTER) { curr_elem = *(void **)curr_elem; } + if (!curr_elem && size) { - /* if null pointer check placeholder and do not follow */ - assert(field->flags & VMS_ARRAY_OF_POINTER); - ret = vmstate_info_nullptr.get(f, curr_elem, size, NULL); - } else if (field->flags & VMS_STRUCT) { - ret = vmstate_load_state(f, field->vmsd, curr_elem, - field->vmsd->version_id); - } else if (field->flags & VMS_VSTRUCT) { - ret = vmstate_load_state(f, field->vmsd, curr_elem, - field->struct_version_id); + /* + * If null pointer found (which should only happen in + * an array of pointers), use null placeholder and do + * not follow. + */ + inner_field = vmsd_create_fake_nullptr_field(field); + } else { + inner_field = field; + } + + if (inner_field->flags & VMS_STRUCT) { + ret = vmstate_load_state(f, inner_field->vmsd, curr_elem, + inner_field->vmsd->version_id); + } else if (inner_field->flags & VMS_VSTRUCT) { + ret = vmstate_load_state(f, inner_field->vmsd, curr_elem, + inner_field->struct_version_id); } else { - ret = field->info->get(f, curr_elem, size, field); + ret = inner_field->info->get(f, curr_elem, size, + inner_field); + } + + /* If we used a fake temp field.. free it now */ + if (inner_field != field) { + g_clear_pointer((gpointer *)&inner_field, g_free); } + if (ret >= 0) { ret = qemu_file_get_error(f); } @@ -311,7 +357,7 @@ static void vmsd_desc_field_start(const VMStateDescription *vmsd, static void vmsd_desc_field_end(const VMStateDescription *vmsd, JSONWriter *vmdesc, - const VMStateField *field, size_t size, int i) + const VMStateField *field, size_t size) { if (!vmdesc) { return; @@ -379,37 +425,89 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd, int size = vmstate_size(opaque, field); uint64_t old_offset, written_bytes; JSONWriter *vmdesc_loop = vmdesc; + bool is_prev_null = false; trace_vmstate_save_state_loop(vmsd->name, field->name, n_elems); if (field->flags & VMS_POINTER) { first_elem = *(void **)first_elem; assert(first_elem || !n_elems || !size); } + for (i = 0; i < n_elems; i++) { void *curr_elem = first_elem + size * i; + const VMStateField *inner_field; + bool is_null; + int max_elems = n_elems - i; - vmsd_desc_field_start(vmsd, vmdesc_loop, field, i, n_elems); old_offset = qemu_file_transferred(f); if (field->flags & VMS_ARRAY_OF_POINTER) { assert(curr_elem); curr_elem = *(void **)curr_elem; } + if (!curr_elem && size) { - /* if null pointer write placeholder and do not follow */ - assert(field->flags & VMS_ARRAY_OF_POINTER); - ret = vmstate_info_nullptr.put(f, curr_elem, size, NULL, - NULL); - } else if (field->flags & VMS_STRUCT) { - ret = vmstate_save_state(f, field->vmsd, curr_elem, - vmdesc_loop); - } else if (field->flags & VMS_VSTRUCT) { - ret = vmstate_save_state_v(f, field->vmsd, curr_elem, - vmdesc_loop, - field->struct_version_id, errp); + /* + * If null pointer found (which should only happen in + * an array of pointers), use null placeholder and do + * not follow. + */ + inner_field = vmsd_create_fake_nullptr_field(field); + is_null = true; + } else { + inner_field = field; + is_null = false; + } + + /* + * Due to the fake nullptr handling above, if there's mixed + * null/non-null data, it doesn't make sense to emit a + * compressed array representation spanning the entire array + * because the field types will be different (e.g. struct + * vs. nullptr). Search ahead for the next null/non-null element + * and start a new compressed array if found. + */ + if (field->flags & VMS_ARRAY_OF_POINTER && + is_null != is_prev_null) { + + is_prev_null = is_null; + vmdesc_loop = vmdesc; + + for (int j = i + 1; j < n_elems; j++) { + void *elem = *(void **)(first_elem + size * j); + bool elem_is_null = !elem && size; + + if (is_null != elem_is_null) { + max_elems = j - i; + break; + } + } + } + + vmsd_desc_field_start(vmsd, vmdesc_loop, inner_field, + i, max_elems); + + if (inner_field->flags & VMS_STRUCT) { + ret = vmstate_save_state(f, inner_field->vmsd, + curr_elem, vmdesc_loop); + } else if (inner_field->flags & VMS_VSTRUCT) { + ret = vmstate_save_state_v(f, inner_field->vmsd, + curr_elem, vmdesc_loop, + inner_field->struct_version_id, + errp); } else { - ret = field->info->put(f, curr_elem, size, field, - vmdesc_loop); + ret = inner_field->info->put(f, curr_elem, size, + inner_field, vmdesc_loop); + } + + written_bytes = qemu_file_transferred(f) - old_offset; + vmsd_desc_field_end(vmsd, vmdesc_loop, inner_field, + written_bytes); + + /* If we used a fake temp field.. free it now */ + if (inner_field != field) { + g_clear_pointer((gpointer *)&inner_field, g_free); } + if (ret) { error_setg(errp, "Save of field %s/%s failed", vmsd->name, field->name); @@ -419,9 +517,6 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd, return ret; } - written_bytes = qemu_file_transferred(f) - old_offset; - vmsd_desc_field_end(vmsd, vmdesc_loop, field, written_bytes, i); - /* Compressed arrays only care about the first element */ if (vmdesc_loop && vmsd_can_compress(field)) { vmdesc_loop = NULL; |