amd64 failed to boot when RAM > 1024MB

[chyh1990]

Description

uCore failed to boot on amd64 with RAM > 1024MB

Commit

a90a7fc Merge branch 'amd64-smp' of https://github.com/chyyuu/ucore_plus

Reproduce Steps

cd ucore
make ARCH=amd64 defconfig
make kernel
make sfsimg
qemu-system-x86_64 -m 1025 -hda obj/kernel.img

Current Result

System reboots when executing src/kern-ucore/arch/amd64/mm/pmm.c:346

Expected Result

Available memory ranges should be successfully detected and managed.