linux-kernel - Re: [GIT PULL] x86/urgent for v5.11-rc7

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Date:   Sun, 7 Feb 2021 12:44:12 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Borislav Petkov <bp@...e.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>, x86-ml <x86@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] x86/urgent for v5.11-rc7

On Sun, Feb 7, 2021 at 10:21 AM Dave Hansen <dave.hansen@...el.com> wrote:
>
> On 2/7/21 9:58 AM, Borislav Petkov wrote:
> > On Sun, Feb 07, 2021 at 09:49:18AM -0800, Linus Torvalds wrote:
> >> On Sun, Feb 7, 2021 at 2:40 AM Borislav Petkov <bp@...e.de> wrote:
> >>> - Disable CET instrumentation in the kernel so that gcc doesn't add
> >>> ENDBR64 to kernel code and thus confuse tracing.
> >> So this is clearly the right thing to do for now, but I wonder if
> >> people have a plan for actually enabling CET and endbr at cpl0 at some
> >> point?
> > It probably is an item on some Intel manager's to-enable list. So far,
> > the CET enablement concentrates only on userspace but dhansen might know
> > more about future plans. CCed.
>
> It's definitely on our radar to look at after CET userspace.

What is the desired timeline to enable CET in the kernel ?
I think for bpf and tracing it will be mostly straightforward to deal
with extra endbr64 insn in front of the fentry nop.
Just trying to figure when this work needs to be done.