linux-kernel - Re: [PATCH] x86/its: use Sapphire Rapids+ feature to opt out

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: <73a22a19-c492-4a75-8352-a4cfac47d812@intel.com>
Date: Tue, 21 Oct 2025 07:01:33 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Jon Kohler <jon@...anix.com>,
 Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>,
 Peter Zijlstra <peterz@...radead.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
 Jonathan Corbet <corbet@....net>, Ingo Molnar <mingo@...hat.com>,
 Dave Hansen <dave.hansen@...ux.intel.com>, "x86@...nel.org"
 <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
 Brian Gerst <brgerst@...il.com>, Brendan Jackman <jackmanb@...gle.com>,
 "Ahmed S. Darwish" <darwi@...utronix.de>,
 Alexandre Chartre <alexandre.chartre@...cle.com>,
 "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/its: use Sapphire Rapids+ feature to opt out

On 10/21/25 06:40, Jon Kohler wrote:
> So to simplify it down:
> A guest VM that updates to a ITS-enabled guest kernel sees performance
> impacts on non-vulnerable hardware, when running on non-BHI_CTRL and/or
> non-ITS_NO hypervisors, which is a very easy situation to get into, especially
> on QEMU with live migration-enabled pools.

By non-$FEATURE, do you mean that they chose to not enumerate those
features, or that they are completely ignorant of them?