linux-kernel - Re: [PATCH v8 00/17] Enable FSGSBASE instructions

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Date:   Mon, 16 Sep 2019 11:21:50 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andy Lutomirski <luto@...nel.org>
cc:     "Chang S. Bae" <chang.seok.bae@...el.com>,
        linux-kernel@...r.kernel.org,
        the arch/x86 maintainers <x86@...nel.org>,
        Borislav Petkov <bp@...en8.de>, dave.hansen@...el.com,
        tony.luck@...el.com, ak@...ux.intel.com, ravi.v.shankar@...el.com
Subject: Re: [PATCH v8 00/17] Enable FSGSBASE instructions

On Thu, 12 Sep 2019, Andy Lutomirski wrote:

Thanks, for adding me and the others on Cc. I had to dig out the cover
letter from my LKML archive ....

> On 9/12/19 1:06 PM, Chang S. Bae wrote:
> 
> > Updates from v7 [7]:
> > (1) Consider FSGSBASE when determining which Spectre SWAPGS mitigations are
> >      required.
> > (2) Fixed save_fsgs() to be aware of interrupt conditions
> > (3) Made selftest changes based on Andy's previous fixes and cleanups
> > (4) Included Andy's paranoid exit cleanup
> > (5) Included documentation rewritten by Thomas
> > (6) Carried on Thomas' edits on multiple changelogs and comments
> > (7) Used '[FS|GS] base' consistently, except for selftest where GSBASE has
> >      been already used in its test messages
> > (8) Dropped the READ_MSR_GSBASE macro
> > 
> 
> This looks unpleasant to review.  I wonder if it would be better to unrevert
> the reversion, merge up to Linus' tree or -tip, and then base the changes on
> top of that.

I don't think that's a good idea. The old code is broken in several ways
and not bisectable. So we really better start from scratch.

Thanks,

	tglx