Hotspot doesn't have a good way to build 64 VM on 64 bit Linux OS. Currently the command used to build 64 bit VM is "gnumake {product|fastdebug|jvmg}" (select one of the targets in {}). This in fact corresponds to how gcc works on these platforms, i.e. the default is to build 64 bit application unless you specify -m32 by yourself. Even though this is nice, it has two problems at least:

1. There is no way to build 32 bit VM even though you pass ARCH_DATA_MODEL=32 or whatever.
2. This is not consistent with other 64 bit OS such as Solaris. On Solaris, passing LP64=1 or ARCH_DATA_MODEL=64 will build 64 bit VM and w/o these options, it will build 32 bit VM by default. This is good in the sense that developer could expect what they could get. 

So it would be nice that we could provide a consistent way to build 64/32 bit VM on these 64 bit operating systems.