The address of a packed member is not packed, which may cause accesses
to unaligned pointers. Avoid this by reading the packed value before
passing it to another function.
Cc: Jason Wang <jasowang@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>