On Mon, Sep 20, 2021 at 6:26 PM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > On 27/08/21 05:12, Zixuan Wang wrote: > > +.globl gdt64 > > +gdt64: > > + .quad 0 > > + .quad 0x00af9b000000ffff /* 64-bit code segment */ > > + .quad 0x00cf93000000ffff /* 32/64-bit data segment */ > > + .quad 0x00af1b000000ffff /* 64-bit code segment, not present */ > > + .quad 0x00cf9b000000ffff /* 32-bit code segment */ > > + .quad 0x008f9b000000FFFF /* 16-bit code segment */ > > + .quad 0x008f93000000FFFF /* 16-bit data segment */ > > + .quad 0x00cffb000000ffff /* 32-bit code segment (user) */ > > + .quad 0x00cff3000000ffff /* 32/64-bit data segment (user) */ > > + .quad 0x00affb000000ffff /* 64-bit code segment (user) */ > > + > > + .quad 0 /* 6 spare selectors */ > > + .quad 0 > > + .quad 0 > > + .quad 0 > > + .quad 0 > > + .quad 0 > > + > > +tss_descr: > > + .rept max_cpus > > + .quad 0x000089000000ffff /* 64-bit avail tss */ > > + .quad 0 /* tss high addr */ > > + .endr > > +gdt64_end: > > > > +.globl tss > > +tss: > > + .rept max_cpus > > + .long 0 > > + .quad 0 > > + .quad 0, 0 > > + .quad 0, 0, 0, 0, 0, 0, 0, 0 > > + .long 0, 0, 0 > > + .endr > > +tss_end: > > + > > Please place the IDT (from the previous patch), GDT and TSS in a common > source file for both UEFI and multiboot. It could in fact be > lib/x86/desc.c even. > > Duplicating the descriptors is fine, since they're only referred from > the startup code. > > Paolo > I will make this update in the next version. I think placing descriptors in lib/x86/desc.c is also a good idea. In this way, compilers can automatically generate position-independent code (PIC) for data structures written in C, and the following descriptor address setup code can be removed. > + /* Set GDT runtime address */ > + lea gdt64(%rip), %rax > + mov %rax, gdt64_desc+2(%rip) Best regards, Zixuan
