353f5ba92f
Reduce reserved memory consumption by page table buffer, then OS can have more available memory to use. Take PhysicalAddressBits = 48 and 2MB page granularity as example, 1:1 Virtual to Physical identity mapping page table buffer needs to be ((512 + 1) * 512 + 1) * 4096 = 1075843072 bytes = 0x40201000 bytes. When BIOS does not support long mode waking vector, only allocate 2 pages (1G page enabled) or 6 pages for 4G page table, and 8 extra pages to handles > 4G request by page fault. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Star Zeng <star.zeng@intel.com> Reviewed-by: Jiewen Yao <jiewen.yao@intel.com> git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18068 6f19259b-4bc3-4df7-8a09-765794883524