exec: fix migration with devices that use address_space_rw

Devices that use address_space_rw to write large areas to memory
(as opposed to address_space_map/unmap) were broken with respect
to migration since fe680d0 (exec: Limit translation limiting in
address_space_translate to xen, 2014-05-07).  Such devices include
IDE CD-ROMs.

The reason is that invalidate_and_set_dirty (called by address_space_rw
but not address_space_map/unmap) was only setting the dirty bit for
the first page in the translation.

To fix this, introduce cpu_physical_memory_set_dirty_range_nocode that
is the same as cpu_physical_memory_set_dirty_range except it does not
muck with the DIRTY_MEMORY_CODE bitmap.  This function can be used if
the caller invalidates translations with tb_invalidate_phys_page_range.

There is another difference between cpu_physical_memory_set_dirty_range
and cpu_physical_memory_set_dirty_flag; the former includes a call
to xen_modified_memory.  This is handled separately in
invalidate_and_set_dirty, and is not needed in other callers of
cpu_physical_memory_set_dirty_range_nocode, so leave it alone.

Just one nit: now that invalidate_and_set_dirty takes care of handling
multiple pages, there is no need for address_space_unmap to wrap it
in a loop.  In fact that loop would now be O(n^2).

Reported-by: Dave Gilbert <dgilbert@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index e9eb831..6593be1 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -71,6 +71,17 @@ static inline void cpu_physical_memory_set_dirty_flag(ram_addr_t addr,
     set_bit(addr >> TARGET_PAGE_BITS, ram_list.dirty_memory[client]);
 }
 
+static inline void cpu_physical_memory_set_dirty_range_nocode(ram_addr_t start,
+                                                              ram_addr_t length)
+{
+    unsigned long end, page;
+
+    end = TARGET_PAGE_ALIGN(start + length) >> TARGET_PAGE_BITS;
+    page = start >> TARGET_PAGE_BITS;
+    bitmap_set(ram_list.dirty_memory[DIRTY_MEMORY_MIGRATION], page, end - page);
+    bitmap_set(ram_list.dirty_memory[DIRTY_MEMORY_VGA], page, end - page);
+}
+
 static inline void cpu_physical_memory_set_dirty_range(ram_addr_t start,
                                                        ram_addr_t length)
 {