Haozhong Zhang <haozhong.zh...@intel.com> wrote:
> In cpu_physical_memory_sync_dirty_bitmap(rb, start, ...), the 2nd
> argument 'start' is relative to the start of the ramblock 'rb'. When
> it's used to access the dirty memory bitmap of ram_list (i.e.
> ram_list.dirty_memory[DIRTY_MEMORY_MIGRATION]->blocks[]), an offset to
> the start of all RAM (i.e. rb->offset) should be added to it, which has
> however been missed since c/s 6b6712efcc. For a ramblock of host memory
> backend whose offset is not zero, cpu_physical_memory_sync_dirty_bitmap()
> synchronizes the incorrect part of the dirty memory bitmap of ram_list
> to the per ramblock dirty bitmap. As a result, a guest with host
> memory backend may crash after migration.
>
> Fix it by adding the offset of ramblock when accessing the dirty memory
> bitmap of ram_list in cpu_physical_memory_sync_dirty_bitmap().
>
> Reported-by: Stefan Hajnoczi <stefa...@redhat.com>
> Signed-off-by: Haozhong Zhang <haozhong.zh...@intel.com>
Reviewed-by: Juan Quintela <quint...@redhat.com>
As this function is only used on migration, should I integrate it on my
next push, or do you want to pull it, Paolo?
Later, Juan.
> ---
> include/exec/ram_addr.h | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
> index 73d1bea8b6..cbc797ed05 100644
> --- a/include/exec/ram_addr.h
> +++ b/include/exec/ram_addr.h
> @@ -377,6 +377,7 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock
> *rb,
> uint64_t *real_dirty_pages)
> {
> ram_addr_t addr;
> + ram_addr_t offset = rb->offset;
> unsigned long page = BIT_WORD(start >> TARGET_PAGE_BITS);
> uint64_t num_dirty = 0;
> unsigned long *dest = rb->bmap;
> @@ -386,8 +387,9 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock
> *rb,
> int k;
> int nr = BITS_TO_LONGS(length >> TARGET_PAGE_BITS);
> unsigned long * const *src;
> - unsigned long idx = (page * BITS_PER_LONG) / DIRTY_MEMORY_BLOCK_SIZE;
> - unsigned long offset = BIT_WORD((page * BITS_PER_LONG) %
> + unsigned long word = BIT_WORD((start + offset) >> TARGET_PAGE_BITS);
> + unsigned long idx = (word * BITS_PER_LONG) / DIRTY_MEMORY_BLOCK_SIZE;
> + unsigned long offset = BIT_WORD((word * BITS_PER_LONG) %
> DIRTY_MEMORY_BLOCK_SIZE);
>
> rcu_read_lock();
> @@ -416,7 +418,7 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock
> *rb,
> } else {
> for (addr = 0; addr < length; addr += TARGET_PAGE_SIZE) {
> if (cpu_physical_memory_test_and_clear_dirty(
> - start + addr,
> + start + addr + offset,
> TARGET_PAGE_SIZE,
> DIRTY_MEMORY_MIGRATION)) {
> *real_dirty_pages += 1;
