Commit 084140bd authored by Haozhong Zhang's avatar Haozhong Zhang Committed by Juan Quintela
Browse files

exec: fix access to ram_list.dirty_memory when sync dirty bitmap 



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 6b6712ef. 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: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarHaozhong Zhang <haozhong.zhang@intel.com>
Message-Id: <20170628083704.24997-1-haozhong.zhang@intel.com>
Reviewed-by: default avatarJuan Quintela <quintela@redhat.com>
Tested-by: default avatarJuan Quintela <quintela@redhat.com>
Tested-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarJuan Quintela <quintela@redhat.com>
parent c788ada8

include/exec/ram_addr.h

+6 −3
Original line number Diff line number Diff line
@@ -386,8 +386,9 @@ 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 + rb->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();
@@ -414,9 +415,11 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb, 


        rcu_read_unlock();

    } else {

        ram_addr_t offset = rb->offset;



        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;