On Mon, May 08, 2023 at 09:44:22PM +0200, Thomas Gleixner wrote: > @@ -252,6 +252,17 @@ SYM_INNER_LABEL(secondary_startup_64_no_ > movq TASK_threadsp(%rax), %rsp > > /* > + * Now that this CPU is running on its own stack, drop the realmode > + * protection. For the boot CPU the pointer is NULL! > + */ > + movq trampoline_lock(%rip), %rax movl $0, (%rax) > +.Lsetup_gdt: > + /* > * We must switch to a new descriptor in kernel space for the GDT > * because soon the kernel won't have access anymore to the userspace > * addresses where we're currently running on. We have to do that here > --- a/arch/x86/realmode/rm/trampoline_64.S > +++ b/arch/x86/realmode/rm/trampoline_64.S > @@ -37,6 +37,24 @@ > .text > .code16 > > +.macro LOAD_REALMODE_ESP > + /* > + * Make sure only one CPU fiddles with the realmode stack > + */ > +.Llock_rm\@: > + btl $0, tr_lock > + jnc 2f > + pause > + jmp .Llock_rm\@ > +2: > + lock > + btsl $0, tr_lock > + jc .Llock_rm\@ Do we really care about performance here; or should we pick the simpler form? Also, 'lock' is a prefix, not an instruction. .Llock_rm\@: lock btsl $0, tr_lock; jnc 2f pause jmp .Llock_rm\@ 2: > + > + # Setup stack > + movl $rm_stack_end, %esp > +.endm > + > .balign PAGE_SIZE
