linux-kernel - Re: [PATCH v2 2/5] x86/idle: Disable IBRS when cpu is offline

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]

Message-ID: <20230621144848.GJ2053369@hirez.programming.kicks-ass.net>
Date:   Wed, 21 Jun 2023 16:48:48 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Len Brown <lenb@...nel.org>, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-pm@...r.kernel.org,
        Robin Jarry <rjarry@...hat.com>, Joe Mario <jmario@...hat.com>
Subject: Re: [PATCH v2 2/5] x86/idle: Disable IBRS when cpu is offline

On Wed, Jun 21, 2023 at 10:44:23AM -0400, Waiman Long wrote:

> Well, hlt_play_dead() is only called if cpuidle_play_dead() returns an error
> which is not the typical case. My testing does confirm that this patch is
> able to keep the IBRS bit off when a CPU is offline via its online sysfs
> file.

The point is; your re-enable IBRS hunk at the end is dead-code. It
should never ever run and having it is confusing.