mmio_hint in mem.c can potentially be accessed concurrently in
emulate_mem() because it only holds a read lock. Use a local variable to
make sure the same entry address is used throughout the function. Since
it only serves as a hint, it's okay if the function does not use the
most up-to-date version of mmio_hint, as long as mmio_hint is accessed
atomically.
Explicitly enforce natural alignment on mmio_hint to guarantee atomic
accesses on x86 and increase code portability, even though compilers
most likely always do it.
Entries in the RB tree are only removed in unregister_mem_int() while
holding a write lock, so accessing mmio_hint while holding a read lock
is safe.
Tracked-On: #2902
Signed-off-by: Peter Fang <peter.fang@intel.com>
Reviewed-by: Shuo A Liu <shuo.a.liu@intel.com>
82fa9946e0