diff --git a/include/qemu/hbitmap.h b/include/qemu/hbitmap.h index eb464759d5..9239fe515e 100644 --- a/include/qemu/hbitmap.h +++ b/include/qemu/hbitmap.h @@ -145,6 +145,19 @@ void hbitmap_reset_all(HBitmap *hb); */ bool hbitmap_get(const HBitmap *hb, uint64_t item); +/** + * hbitmap_is_serializable: + * @hb: HBitmap which should be (de-)serialized. + * + * Returns whether the bitmap can actually be (de-)serialized. Other + * (de-)serialization functions may only be invoked if this function returns + * true. + * + * Calling (de-)serialization functions does not affect a bitmap's + * (de-)serializability. + */ +bool hbitmap_is_serializable(const HBitmap *hb); + /** * hbitmap_serialization_granularity: * @hb: HBitmap to operate on. diff --git a/tests/test-hbitmap.c b/tests/test-hbitmap.c index 9b7495cc32..23773d2051 100644 --- a/tests/test-hbitmap.c +++ b/tests/test-hbitmap.c @@ -744,6 +744,8 @@ static void test_hbitmap_serialize_granularity(TestHBitmapData *data, int r; hbitmap_test_init(data, L3 * 2, 3); + g_assert(hbitmap_is_serializable(data->hb)); + r = hbitmap_serialization_granularity(data->hb); g_assert_cmpint(r, ==, 64 << 3); } @@ -768,6 +770,8 @@ static void hbitmap_test_serialize_range(TestHBitmapData *data, if (count) { hbitmap_set(data->hb, pos, count); } + + g_assert(hbitmap_is_serializable(data->hb)); hbitmap_serialize_part(data->hb, buf, 0, data->size); /* Serialized buffer is inherently LE, convert it back manually to test */ @@ -788,6 +792,8 @@ static void hbitmap_test_serialize_range(TestHBitmapData *data, memset(buf, 0, buf_size); hbitmap_serialize_part(data->hb, buf, 0, data->size); hbitmap_reset_all(data->hb); + + g_assert(hbitmap_is_serializable(data->hb)); hbitmap_deserialize_part(data->hb, buf, 0, data->size, true); for (i = 0; i < data->size; i++) { @@ -810,6 +816,7 @@ static void test_hbitmap_serialize_basic(TestHBitmapData *data, int num_positions = sizeof(positions) / sizeof(positions[0]); hbitmap_test_init(data, L3, 0); + g_assert(hbitmap_is_serializable(data->hb)); buf_size = hbitmap_serialization_size(data->hb, 0, data->size); buf = g_malloc0(buf_size); @@ -841,6 +848,8 @@ static void test_hbitmap_serialize_part(TestHBitmapData *data, hbitmap_set(data->hb, positions[i], 1); } + g_assert(hbitmap_is_serializable(data->hb)); + for (i = 0; i < data->size; i += buf_size) { unsigned long *el = (unsigned long *)buf; hbitmap_serialize_part(data->hb, buf, i, buf_size); @@ -879,6 +888,8 @@ static void test_hbitmap_serialize_zeroes(TestHBitmapData *data, hbitmap_set(data->hb, positions[i], L1); } + g_assert(hbitmap_is_serializable(data->hb)); + for (i = 0; i < num_positions; i++) { hbitmap_deserialize_zeroes(data->hb, positions[i], min_l1, true); hbitmap_iter_init(&iter, data->hb, 0); diff --git a/util/hbitmap.c b/util/hbitmap.c index 9f691b76bd..35088e19c4 100644 --- a/util/hbitmap.c +++ b/util/hbitmap.c @@ -387,6 +387,24 @@ void hbitmap_reset_all(HBitmap *hb) hb->count = 0; } +bool hbitmap_is_serializable(const HBitmap *hb) +{ + /* Every serialized chunk must be aligned to 64 bits so that endianness + * requirements can be fulfilled on both 64 bit and 32 bit hosts. + * We have hbitmap_serialization_granularity() which converts this + * alignment requirement from bitmap bits to items covered (e.g. sectors). + * That value is: + * 64 << hb->granularity + * Since this value must not exceed UINT64_MAX, hb->granularity must be + * less than 58 (== 64 - 6, where 6 is ld(64), i.e. 1 << 6 == 64). + * + * In order for hbitmap_serialization_granularity() to always return a + * meaningful value, bitmaps that are to be serialized must have a + * granularity of less than 58. */ + + return hb->granularity < 58; +} + bool hbitmap_get(const HBitmap *hb, uint64_t item) { /* Compute position and bit in the last layer. */ @@ -399,9 +417,7 @@ bool hbitmap_get(const HBitmap *hb, uint64_t item) uint64_t hbitmap_serialization_granularity(const HBitmap *hb) { - /* Must hold true so that the shift below is defined - * (ld(64) == 6, i.e. 1 << 6 == 64) */ - assert(hb->granularity < 64 - 6); + assert(hbitmap_is_serializable(hb)); /* Require at least 64 bit granularity to be safe on both 64 bit and 32 bit * hosts. */