Jakob: I need more help,just now,I'm trigger a page fault in 64-bit mode,see this picture: https://github.com/krishna116/test/blob/master/test-qemu-in-64bit-mode.png
so I can write some system mode code accroding to this information, but my follow code seems can't get the right answer, is my algorithm wrong? //this is my algorithm in 64-bit mode: #define CS_L_BIT 0x1<<(32+22-1) //CS_selector_index=0x7; //0x38>>3 //GDTR_base=0x7E90000; //0x7e9f598&~0xffff int64* segment_descriptor_address=(int64*)(int64) (*(0x7E90000+0x7*8*2)); //GDTR_base+CS_selector_index* sizeof(Segment_Descriptor*2) if((*segment_descriptor_address)&CS_L_BIT) { //it is 64bit mode }else { //it is Compatibility mode } thank you, krishna