linux-hardening - Re: [PATCH v4 0/5] Next revision of the L1D flush patches

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Date:   Fri, 4 Jun 2021 20:06:14 +1000
From:   Balbir Singh <bsingharora@...il.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "jpoimboe@...hat.com" <jpoimboe@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "dave.hansen@...el.com" <dave.hansen@...el.com>,
        "thomas.lendacky@....com" <thomas.lendacky@....com>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH v4 0/5] Next revision of the L1D flush patches

On Wed, Apr 28, 2021 at 01:08:05PM -0700, Kees Cook wrote:
> On Tue, Apr 27, 2021 at 12:24:16AM +0200, Thomas Gleixner wrote:
> > On Mon, Apr 26 2021 at 10:31, Thomas Gleixner wrote:
> > > On Thu, Apr 08 2021 at 13:23, Kees Cook wrote:
> > >>
> > >> I'd still really like to see this -- it's a big hammer, but that's the
> > >> point for cases where some new flaw appears and we can point to the
> > >> toolbox and say "you can mitigate it with this while you wait for new
> > >> kernel/CPU."
> > >>
> > >> Any further thoughts from x86 maintainers? This seems like it addressed
> > >> all of tglx's review comments.
> > >
> > > Sorry for dropping the ball on this. It's in my list of things to deal
> > > with. Starting to look at it now.
> > 
> > So I went through the pile and for remorse I sat down and made the
> > tweaks I think are necessary myself.
> > 
> > I've pushed out the result to
> > 
> >   git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git x86/l1dflush
> 
> Oh excellent; thank you for doing this!
>

Thanks again Thomas!

I no longer have access to the bare metal hardware, but I was able to test
this under qemu with some emulation changes. The changes worked as expected.

Folks on the list/cc, appreciate any tested-by or additional reviewed-by
tags if you do happen to review/test.

Thanks,
Balbir Singh.