From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752699AbdKHQSK convert rfc822-to-8bit (ORCPT ); Wed, 8 Nov 2017 11:18:10 -0500 Received: from email2.exegy.com ([216.33.75.132]:45689 "EHLO email2.exegy.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751944AbdKHQSJ (ORCPT ); Wed, 8 Nov 2017 11:18:09 -0500 X-Greylist: delayed 370 seconds by postgrey-1.27 at vger.kernel.org; Wed, 08 Nov 2017 11:18:09 EST To: linux-kernel From: "Mr. Berkley Shands" Subject: VDSO and Intel Skylake Virtualization Message-ID: Date: Wed, 8 Nov 2017 10:11:55 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8BIT Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org FYI: We discovered the clock_gettime(CLOCK_REALTIME, &ts); was taking > 6900 cycles to run on intel skylake cpus. Normal is ~60 cycles. In the kernel vdso code is a very nice comment about 1:1 paring in the hypervisor or the syscall would be eventually used. Sorry, but with no hypervisor running, the vdso call will always time out and call the syscall. Disabling the Intel Virtualization in the BIOS corrects this issue, and the clock_gettime() runs as it should. It appears that many folks have run into this issue, and are looking for a solution. Should the kernel check to see if there is a hypervisor before getting confused in __vdso_clock_gettime() ? Berkley -- //E. F. Berkley Shands, MSc Senior Software Architect/Engineer Exegy Systems Engineering// **Exegy Inc.** 349 Marshall Road, Suite 100 St. Louis , MO 63119 Direct: (314) 218-3600 X450 Cell: (314) 303-2546 Office: (314) 218-3600 Fax: (314) 218-3601 The Usual Disclaimer follows... ________________________________ This e-mail and any documents accompanying it may contain legally privileged and/or confidential information belonging to Exegy, Inc. Such information may be protected from disclosure by law. The information is intended for use by only the addressee. If you are not the intended recipient, you are hereby notified that any disclosure or use of the information is strictly prohibited. If you have received this e-mail in error, please immediately contact the sender by e-mail or phone regarding instructions for return or destruction and do not use or disclose the content to others.