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

[H. Peter Anvin]

On January 25, 2024 1:57:18 AM PST, Andi Kleen <ak@xxxxxxxxxxxxxxx> wrote:
>> +	/* 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
>

Agreed.