[PATCH] x86/uaccess: Avoid barrier_nospec() in copy_from_user()

[Kirill A. Shutemov]

On Mon, Oct 21, 2024 at 07:36:50PM -0700, Linus Torvalds wrote:
> On Mon, 21 Oct 2024 at 03:48, Kirill A. Shutemov <kirill at shutemov.name> wrote:
> >
> > LAM brings own speculation issues[1] that is going to be addressed by
> > LASS[2]. There was a patch[3] to disable LAM until LASS is landed, but it
> > never got applied for some reason.
> 
> Bah., I think the reason was that nobody knew what - if any - any hardware.
> 
> I did find an Intel "Product Brief" for "Intel® Xeon® 6 processors
> with E-cores" that claim both LASS and LAM, but that one puts LAM as a
> "security feature", so that seems a bit confused. That's Redwood Cove
> cores, I think.
> 
> I guess that should mean that Meteor Lake ("Core Ultra") should also
> have it? Or is it then turned off because the E cores don't do it?

No, Meteor Lake doesn't support neither LAM nor LASS.

So far, according to SDM, it is supported by Sierra Forest (E-core based
Xeons) and Lunar Lake.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov