From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x224U5LvoXq9d92HqHf0SJI34ITVfRAawCsO+UVjqHfuN7T7kL6CIrsVnm06+13fiXz518hfj ARC-Seal: i=1; a=rsa-sha256; t=1516981007; cv=none; d=google.com; s=arc-20160816; b=RIlLXjqgBL5onSnd6Ix8KJpYFPbnMXc3zDD91N1//3GOtuEstd8QVcbrVekRcT/gKH 95IYkHrHtMHmXAvFmfGSLJc/bCxYziNdARV8OGtNpIKkhL43Z5BLazcRKGOEIi/qrKVj dMrvUsFMgctz/opX98VrCeP2WIhZjRu3Cq5JHbnliq8WVPYTsYou3pio2RqQYjnjJMz7 X2OvtIEbDaLdJ3/d79aPe1l1Mg7F3zbUia4qeysBfu0MDIbhM8rxbd8oLkUda2oW3D6b N6B+q4xNSzJUbk8U9EIkund81sYuc0sWK6Va/YhEb7vchQuVR6G14LKKJ9MnWvAqb5RL zjvw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:user-agent:content-disposition :mime-version:message-id:subject:to:from:date:dkim-signature :arc-authentication-results; bh=UlbdIn+7n0RCDNPcKybiGrdHD51bQuJFnsB7ojvy5+o=; b=CbNT/3gz96HZFnxcg9SM3ZR52EAWzn24bvmrCNmPZmc+5nXdfs4g/TvqR5wxatVpaM VZK3yBv3hKz/c62sfXUgAv1oMuTkyYZrtwrwdoMGi2PglA+xzLQrIpGP1LhlN/JJ5e6Y ZymZL2y9/3H9pxILqY4mG+dnqYmb+ocbo161oOCQlqZjeWwZFx5I9JN9oebFLGism1Yu xCl0jFRm35mqyEbCKcsknTWPfQwOSPNaxMWiaOwbcUbzC1JtcUi8EgHOSNa2WxwaSyeA lhEQg68Tzrmwg1aiuUUueKM+xdKkhIZWZEHEXq6Fwzwk3dLKxH8WbYt6/AmD4rhM43Pn 7h5w== ARC-Authentication-Results: i=1; mx.google.com; dkim=neutral (body hash did not verify) header.i=@linaro.org header.s=google header.b=GbBKXzvQ; spf=pass (google.com: best guess record for domain of linux-kselftest-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kselftest-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=linaro.org Authentication-Results: mx.google.com; dkim=neutral (body hash did not verify) header.i=@linaro.org header.s=google header.b=GbBKXzvQ; spf=pass (google.com: best guess record for domain of linux-kselftest-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kselftest-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752495AbeAZPge (ORCPT ); Fri, 26 Jan 2018 10:36:34 -0500 Received: from mail-io0-f180.google.com ([209.85.223.180]:42982 "EHLO mail-io0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751647AbeAZPgd (ORCPT ); Fri, 26 Jan 2018 10:36:33 -0500 Date: Fri, 26 Jan 2018 09:36:31 -0600 From: Dan Rue To: Shuah Khan , Ingo Molnar , Andy Lutomirski , Dmitry Safonov , Borislav Petkov , linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: selftests/x86/fsgsbase_64 test problem Message-ID: <20180126153631.ha7yc33fj5uhitjo@xps> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: NeoMutt/20171215 Sender: linux-kselftest-owner@vger.kernel.org X-Mailing-List: linux-kselftest@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1590669876861238825?= X-GMAIL-MSGID: =?utf-8?q?1590669876861238825?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: We've noticed that fsgsbase_64 can fail intermittently with the following error: [RUN] ARCH_SET_GS(0x0) and clear gs, then schedule to 0x1 Before schedule, set selector to 0x1 other thread: ARCH_SET_GS(0x1) -- sel is 0x0 [FAIL] GS/BASE changed from 0x1/0x0 to 0x0/0x0 This can be reliably reproduced by running fsgsbase_64 in a loop. i.e. for i in $(seq 1 10000); do ./fsgsbase_64 || break; done This problem isn't new - I've reproduced it on latest mainline and every release going back to v4.12 (I did not try earlier). This was tested on a Supermicro board with a Xeon E3-1220 as well as an Intel Nuc with an i3-5010U. Thanks, Dan