Re: [PATCH v11 9/9] x86/cpu: Enable LASS by default during CPU initialization

[David Laight]

On Thu, 30 Oct 2025 09:44:02 -0700
Sohil Mehta <sohil.mehta@xxxxxxxxx> wrote:

> On 10/30/2025 8:45 AM, Andy Lutomirski wrote:
> > On Thu, Oct 30, 2025, at 1:40 AM, H. Peter Anvin wrote:  
> >> Legacy vsyscalls have been obsolete for how long now?  
> > 
> > A looooong time.
> > 
> > I would suggest defaulting LASS to on and *maybe* decoding just enough to log, once per boot, that a legacy vsyscall may have been attempted. It’s too bad that #GP doesn’t report the faulting address.
> >   
> 
> Unfortunately, CONFIG_X86_VSYSCALL_EMULATION defaults to y. Also, the
> default Vsyscall mode is XONLY. So even if vsyscalls are deprecated,
> there is a non-zero possibility someone would complain about it.

Presumably a command line parameter could be used to disable LASS
in order to enable vsyscall emulation?

That might let LASS be enabled by default.

	David