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From:   Andy Lutomirski <luto@kernel.org>
Date:   Wed, 6 Jun 2018 10:11:06 -0700
Message-ID: <CALCETrV+qJMZJrnb3fTWVaDAGRR0RXoVThMj6BgbdPnM1xa-Ng@mail.gmail.com>
Subject: Re: [PATCH v2 5/8] x86/msr: write_rdtscp_aux() to use wrmsr_safe()
To:     "Bae, Chang Seok" <chang.seok.bae@intel.com>
Cc:     Andrew Lutomirski <luto@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>,
        Andi Kleen <ak@linux.intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "Metzger, Markus T" <markus.t.metzger@intel.com>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        LKML <linux-kernel@vger.kernel.org>
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On Wed, Jun 6, 2018 at 9:23 AM Chang S. Bae <chang.seok.bae@intel.com> wrote:
>
> Using wrmsr_safe() can make code a bit simpler by removing
> some condition check

NAK.

If we really want to stop checking the cpu feature and unconditionally
write the MSR, then there should be a single patch that does it.  If
we don't, then we should not make this change, since it will make the
very useful warning  if we screwed it up go away.

I think we should continue checking the cpu feature, personally.  I
also thing that, if we make the change, it should not be part of the
FSGSBASE series.