From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linutronix.de (146.0.238.70:993) by crypto-ml.lab.linutronix.de with IMAP4-SSL for ; 12 Dec 2018 18:47:30 -0000 Received: from mail-lj1-x244.google.com ([2a00:1450:4864:20::244]) by Galois.linutronix.de with esmtps (TLS1.2:RSA_AES_128_CBC_SHA1:128) (Exim 4.80) (envelope-from ) id 1gX9Xd-0007GA-37 for speck@linutronix.de; Wed, 12 Dec 2018 19:47:29 +0100 Received: by mail-lj1-x244.google.com with SMTP id k19-v6so17169285lji.11 for ; Wed, 12 Dec 2018 10:47:29 -0800 (PST) References: <0d6a3fbe4c511152a0f5350e62e9e09ec545f709.1544464266.git.ak@linux.intel.com> <20181211000303.GB16024@tassilo.jf.intel.com> <20181211032503.GB25620@tassilo.jf.intel.com> <20181212175803.GF25620@tassilo.jf.intel.com> In-Reply-To: <20181212175803.GF25620@tassilo.jf.intel.com> From: Linus Torvalds Date: Wed, 12 Dec 2018 10:47:10 -0800 Message-ID: Subject: [MODERATED] Re: [PATCH v2 3/8] MDSv2 5 Content-Type: text/plain; charset="UTF-8" To: speck@linutronix.de List-ID: [ let's see if this comes through now ] On Wed, Dec 12, 2018, 09:58 speck for Andi Kleen > However there is one problem: if the guest is using > the software sequence and the sequence gets interrupted > by an exit, > So I'm at the Intel partner meeting right now, and the official statement seems to be that the software sequence really shouldn't be used. Nobody seems to want that to be used for anything but something really odd case. Just the verw instruction seems to be on the order of 400 cycles. It's probably unnoticeable on any machine that has all the other mitigations in place, but it looks like there are machines now that have all the other things fixed, so 400 cycles then is still quite noticeable. But the software sequence really sounds like nobody should realistically be using by default. Linus >