When Xen was made relocatable, some code are broken. This patch set addresses on it.

I went little further. Some of the assembler functions related to context switch maps stack, others doesn't. It isn't consistent. So there were two choice for consistency. My choice is mapping stacks. After that, it isn't necessary that stack is allocated from xenheap. Allocate stack from domheap, thus memory pressure on xenheap was reduced.

To be honest I didn't test the mca patch(). Kazuhiro, Could you please review and test it?

thanks