Merge branch 'chenyh/amd64' of github.com:chyyuu/ucore_plus into chenyh/amd64
Merge branch 'chenyh/amd64' of github.com:chyyuu/ucore_plus into chenyh/amd64
Merge branch 'chenyh/amd64' of github.com:chyyuu/ucore_plus into chenyh/amd64
Boot APs

Now the AP spins after boot-up. Share pagetable with BSP.
XXX: longmode_ap_entry  will raise #GP if stack > 1GB (only map 1G in boot pgd)
Merge branch 'chenyh/amd64' of github.com:chyyuu/ucore_plus into chenyh/amd64
Merge branch 'chenyh/amd64' into amd64-smp
add sys_halt syscall and  user app: halt.c. So in qemu-no-graphic mode, we can exec halt to quit the qemu environment. USE  make runamd64 ; update out info for e820map and pagetable