Xen compilation

When I was trying to compile Xen-4.0.1, I got these messages:

make[1]: Entering directory `/xen-4.0-testing.hg/xen'
make -f Rules.mk _install
make[2]: Entering directory `/xen-4.0-testing.hg/xen'
make -C tools
make[3]: Entering directory `/xen-4.0-testing.hg/xen/tools'
[ -d figlet ] && make -C figlet
make[4]: Entering directory `/xen-4.0-testing.hg/xen/tools/figlet'
make[4]: `figlet' is up to date.
make[4]: Leaving directory `/xen-4.0-testing.hg/xen/tools/figlet'
make symbols
make[4]: Entering directory `/xen-4.0-testing.hg/xen/tools'
make[4]: `symbols' is up to date.
make[4]: Leaving directory `/xen-4.0-testing.hg/xen/tools'
make[3]: Leaving directory `/xen-4.0-testing.hg/xen/tools'
make -f /xen-4.0-testing.hg/xen/Rules.mk include/xen/compile.h
make[3]: Entering directory `/xen-4.0-testing.hg/xen'
 __  __            _  _    ___   ____              _                   
 \ \/ /___ _ __   | || |  / _ \ |___ \    _ __ ___/ |   _ __  _ __ ___ 
  \  // _ \ '_ \  | || |_| | | |  __) |__| '__/ __| |__| '_ \| '__/ _ \
  /  \  __/ | | | |__   _| |_| | / __/|__| | | (__| |__| |_) | | |  __/
 /_/\_\___|_| |_|    |_|(_)___(_)_____|  |_|  \___|_|  | .__/|_|  \___|
                                                       |_|             
make[3]: Leaving directory `/xen-4.0-testing.hg/xen'
[ -e include/asm ] || ln -sf asm-x86 include/asm
make -f /xen-4.0-testing.hg/xen/Rules.mk -C include
make[3]: Entering directory `/xen-4.0-testing.hg/xen/include'
make[3]: Nothing to be done for `all'.
make[3]: Leaving directory `/xen-4.0-testing.hg/xen/include'
make -f /xen-4.0-testing.hg/xen/Rules.mk -C arch/x86 asm-offsets.s
make[3]: Entering directory `/xen-4.0-testing.hg/xen/arch/x86'
make[3]: `asm-offsets.s' is up to date.
make[3]: Leaving directory `/xen-4.0-testing.hg/xen/arch/x86'
make -f /xen-4.0-testing.hg/xen/Rules.mk include/asm-x86/asm-offsets.h
make[3]: Entering directory `/xen-4.0-testing.hg/xen'
make[3]: `include/asm-x86/asm-offsets.h' is up to date.
make[3]: Leaving directory `/xen-4.0-testing.hg/xen'
make -f /xen-4.0-testing.hg/xen/Rules.mk -C arch/x86 /xen-4.0-testing.hg/xen/xen
make[3]: Entering directory `/xen-4.0-testing.hg/xen/arch/x86'
make -f /xen-4.0-testing.hg/xen/Rules.mk -C /xen-4.0-testing.hg/xen/arch/x86/boot built_in.o
make[4]: Entering directory `/xen-4.0-testing.hg/xen/arch/x86/boot'
RELOC=0x7c000 XEN_BITSPERLONG=64 make -f build32.mk reloc.S
make[5]: Entering directory `/xen-4.0-testing.hg/xen/arch/x86/boot'
make[5]: *** ../../../../.config: Is a directory.  Stop.
make[5]: Leaving directory `/xen-4.0-testing.hg/xen/arch/x86/boot'
make[4]: *** [reloc.S] Error 2
make[4]: Leaving directory `/xen-4.0-testing.hg/xen/arch/x86/boot'
make[3]: *** [/xen-4.0-testing.hg/xen/arch/x86/boot/built_in.o] Error 2
make[3]: Leaving directory `/xen-4.0-testing.hg/xen/arch/x86'
make[2]: *** [/xen-4.0-testing.hg/xen/xen] Error 2
make[2]: Leaving directory `/xen-4.0-testing.hg/xen'
make[1]: *** [install] Error 2
make[1]: Leaving directory `/xen-4.0-testing.hg/xen'
make: *** [install-xen] Error 2

The message showed me that it was expecting the .config exist in the root folder. I copied the file from /usr/src/linux (kernel source) and recompile. it worked!