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Date:   Wed, 12 Dec 2018 10:59:38 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     "Lendacky, Thomas" <Thomas.Lendacky@amd.com>,
        "x86@kernel.org" <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Jiri Kosina <jkosina@suse.cz>, Ingo Molnar <mingo@redhat.com>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        David Woodhouse <dwmw@amazon.co.uk>
Subject: Re: [PATCH v2] x86/speculation: Add support for STIBP always-on
 preferred mode
Message-ID: <20181212095938.GA6653@zn.tnic>
References: <20181211224615.5373.65736.stgit@tlendack-t1.amdoffice.net>
 <20181212000518.GX27375@zn.tnic>
 <alpine.DEB.2.21.1812111910520.22893@nanos.tec.linutronix.de>
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On Tue, Dec 11, 2018 at 07:37:26PM -0800, Thomas Gleixner wrote:
> Hmmm. I've not seen the V1 of this (it's not in my inbox) but the v1->v2
> changes contain:

You're on CC:

https://lkml.kernel.org/r/20181211190959.28321.56433.stgit@tlendack-t1.amdoffice.net

> 
> > > - Removed explicit SPECTRE_V2_USER_STRICT_PREFERRED mode
> 
> Now I really have to ask why?
> 
> Neither the extra variable nor the cpu feature check are pretty. An
> explicit mode is way better in terms of code clarity and you get the proper
> printout via spectre_v2_user_strings.

Actually, now that I've slept on it, I think we should do this just
like X86_FEATURE_IBRS_ENHANCED - as a modifier for SPECTRE_V2_CMD_AUTO
or _FORCE options.

And that has its own mode SPECTRE_V2_IBRS_ENHANCED.

Makes sense?

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.