linux-kernel - Re: [PATCH v2 5/8] x86/msr: write_rdtscp_aux() to use wrmsr

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 6 Jun 2018 10:11:06 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     "Bae, Chang Seok" <chang.seok.bae@...el.com>
Cc:     Andrew Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Metzger, Markus T" <markus.t.metzger@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 5/8] x86/msr: write_rdtscp_aux() to use wrmsr_safe()

On Wed, Jun 6, 2018 at 9:23 AM Chang S. Bae <chang.seok.bae@...el.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.