Re: [PATCH RESEND] x86/speculation: Fix user-mode spectre-v2 protection with KERNEL_IBRS

Josh Poimboeuf
2023-02-20T17:59:36Z

On Mon, Feb 20, 2023 at 06:46:04PM +0100, Borislav Petkov wrote:
> On Mon, Feb 20, 2023 at 08:34:42AM -0800, Josh Poimboeuf wrote:
> > We will never enable IBRS in user space. We tried that years ago and it
> > was very slow.
>
> Then I don't know what this is trying to fix.
>
> We'd need a proper bug statement in the commit message what the problem
> is. As folks have established, the hw vuln mess is a whole universe of
> crazy. So without proper documenting, this spaghetti madness will be
> completely unreadable.

Agreed, and there seems to be a lot of confusion around this patch. I
think I understand the issue, let me write up a new patch which is
hopefully clearer.

--
Josh