Re: [PATCH 5/5] x86/mm/kaiser: Disable the SYSCALL-64 trampoline along with KAISER

[Dave Hansen]

On 11/27/2017 02:31 PM, Peter Zijlstra wrote:
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -1442,7 +1442,10 @@ void syscall_init(void)
>  		(entry_SYSCALL_64_trampoline - _entry_trampoline);
>  
>  	wrmsr(MSR_STAR, 0, (__USER32_CS << 16) | __KERNEL_CS);
> -	wrmsrl(MSR_LSTAR, SYSCALL64_entry_trampoline);
> +	if (kaiser_enabled)
> +		wrmsrl(MSR_LSTAR, SYSCALL64_entry_trampoline);
> +	else
> +		wrmsrl(MSR_LSTAR, (unsigned long)entry_SYSCALL_64);

Heh, ask and ye shall receive, I guess.

We do need a Documentation/ update now.  For this, and other things.
I'll put something together.