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 ; 08 Feb 2019 00:51:10 -0000 Received: from smtp.eu.citrix.com ([185.25.65.24]) by Galois.linutronix.de with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1gruNp-0007O0-B8 for speck@linutronix.de; Fri, 08 Feb 2019 01:51:09 +0100 Subject: [MODERATED] Re: [SUSPECTED SPAM][PATCH v3 2/6] PERFv3 References: <3dd5d6e2bc9ac53f826c251c68ce84fcc79a6872.1549582769.git.ak@linux.intel.com> From: Andrew Cooper Message-ID: Date: Fri, 8 Feb 2019 00:51:01 +0000 MIME-Version: 1.0 In-Reply-To: <3dd5d6e2bc9ac53f826c251c68ce84fcc79a6872.1549582769.git.ak@linux.intel.com> Content-Type: multipart/mixed; boundary="gy4FGm905WhyAnPTWlMD472cpaACnFoTy"; protected-headers="v1" To: speck@linutronix.de List-ID: --gy4FGm905WhyAnPTWlMD472cpaACnFoTy Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-GB On 07/02/2019 23:41, speck for Andi Kleen wrote: > This patch assumes that the kernel is using > RETPOLINE (or IBRS), otherwise speculative execution could > still corrupt counter 3 in very unlikely cases. What has the kernel configuration got to do with it? It is my understanding that any execution of an XBEGIN instruction, even speculatively, even in userspace will result in PCR3 getting modified. A CPU either has force abort mode active, or PCR3 can be changed behind the kernel's back. ~Andrew --gy4FGm905WhyAnPTWlMD472cpaACnFoTy--