The fast path of cpu_physical_memory_sync_dirty_bitmap() directly manipulates the dirty bitmap. Use atomic_xchg() to make the test-and-clear atomic.
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> --- include/exec/ram_addr.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h index cdcbe9a..3d2a4c1 100644 --- a/include/exec/ram_addr.h +++ b/include/exec/ram_addr.h @@ -195,13 +195,13 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(unsigned long *dest, unsigned long *src = ram_list.dirty_memory[DIRTY_MEMORY_MIGRATION]; for (k = page; k < page + nr; k++) { - if (src[k]) { + unsigned long bits = atomic_xchg(&src[k], 0); + if (bits) { unsigned long new_dirty; new_dirty = ~dest[k]; - dest[k] |= src[k]; - new_dirty &= src[k]; + dest[k] |= bits; + new_dirty &= bits; num_dirty += ctpopl(new_dirty); - src[k] = 0; } } } else { -- 2.1.0