Re: [PATCHv3, RESEND] x86/trampoline: Bypass compat mode in trampoline_start64() if not needed

From: Andi Kleen
Date: Thu Jan 25 2024 - 04:57:27 EST


> + /* Paging mode is correct proceed in 64-bit mode */
> +
> + LOCK_AND_LOAD_REALMODE_ESP lock_rip=1
> +
> + movw $__KERNEL_DS, %dx
> + movl %edx, %ss
> + addl $pa_real_mode_base, %esp
> + movl %edx, %ds
> + movl %edx, %es
> + movl %edx, %fs
> + movl %edx, %gs
> +
> + movl $pa_trampoline_pgd, %eax
> + movq %rax, %cr3
> +
> + jmpq *tr_start(%rip)

Still think we should add a far jump here so that we run on a defined
code segment. It probably doesn't matter since there are likely no
IRETs before reloading anyways, but it seems cleaner.

-Andi