crash in virt_to_pages

Hi, I am trying to solve crash on old patched 2.6.18 kernel where virt_to_page() used on stack variable address. function() { struct { u32 ... u32 ... ... } bla; ... = virt_to_page(&bla); } i386 it works fine but x86_64 kernl panics. When kernel panics, &bla is something like ffffffff80574d40, which is not valid for virt_to_pages, AFAIK. Any ideas? Why it is not save to use virt_to_pages on stack addresses? Thank you