linux-kernel - Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf

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:   Sat, 9 Sep 2017 11:26:27 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Markus Trippelsdorf <markus@...ppelsdorf.de>
Cc:     Borislav Petkov <bp@...en8.de>, Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf

On Sat, Sep 9, 2017 at 11:14 AM, Markus Trippelsdorf
<markus@...ppelsdorf.de> wrote:
>
> I think the issue gets fixed by:
>
>  # wrmsr -a 0xc0010015 0x1000018
>
> Setting bit 3 of the Hardware Configuration Register to 1.
>
> Quote for the docs:
> »TlbCacheDis: cacheable memory disable. Read-write. 0=Enables performance optimization that
> assumes PML4, PDP, PDE, and PTE entries are in cacheable WB-DRAM

Uhhuh.

The page directories should *definitely* always be in cacheable
memory, so it should be ok for that bit to be 0, and it's possible
that setting it to 1 will seriously screw up performance.

But the fact that that fixes it for you does indicate that it's not
just a stale TLB entry or something, it really is some CPU using page
tables after they have been free'd and been re-allocated to something
else (and *then* they may point to garbage).

So I do think it's a sign that we definitely need that IPI for you.

                Linus