From: Igor Mitsyanko Date: Fri, 10 Aug 2012 14:45:11 +0000 (+0400) Subject: exec.c: fix dirty bitmap reallocation X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=5fda043f9c8b8ab18da2704de8e77b7c86fa9435;p=qemu.git exec.c: fix dirty bitmap reallocation For each newly created RAM block, dirty bitmap is reallocated with g_realloc, which doesn't make any promises on initial content of new extra data in returned buffer. In theory, we initialize this new data with cpu_physical_memory_set_dirty_range() call. The problem is, cpu_physical_memory_set_dirty_range() has a side effect of incrementing ram_list.dirty_pages variable, but only for pages which are not already dirty. And page "cleanliness" is determined using the same not yet uninitialized dirty bitmap we've just reallocated. This results in inconsistency between real dirty page number and value in ram_list.dirty_pages variable, which in turn could (and will) result in errors during VM migration. Zero initialize new dirty bitmap bytes to fix this problem. Signed-off-by: Igor Mitsyanko Signed-off-by: Blue Swirl --- diff --git a/exec.c b/exec.c index a42a0b5b78..929db5cf0a 100644 --- a/exec.c +++ b/exec.c @@ -2550,6 +2550,8 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host, ram_list.phys_dirty = g_realloc(ram_list.phys_dirty, last_ram_offset() >> TARGET_PAGE_BITS); + memset(ram_list.phys_dirty + (new_block->offset >> TARGET_PAGE_BITS), + 0, size >> TARGET_PAGE_BITS); cpu_physical_memory_set_dirty_range(new_block->offset, size, 0xff); if (kvm_enabled())