Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752763AbdL1Lt1 (ORCPT ); Thu, 28 Dec 2017 06:49:27 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:60897 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751244AbdL1Lt0 (ORCPT ); Thu, 28 Dec 2017 06:49:26 -0500 Date: Thu, 28 Dec 2017 12:49:22 +0100 (CET) From: Thomas Gleixner To: Jiri Bohac cc: Ingo Molnar , "H. Peter Anvin" , Borislav Petkov , linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86_64: use HPET in 64-bit mode to avoid a harware 32-bit wraparound bug In-Reply-To: <20171208171700.pbridtbt3tkvjbhi@dwarf.suse.cz> Message-ID: References: <20171208171700.pbridtbt3tkvjbhi@dwarf.suse.cz> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 523 Lines: 16 On Fri, 8 Dec 2017, Jiri Bohac wrote: > This patch changes the HPET clockevent code to use the Timer 0 in 64-bit > mode (if compiled for x86_64; doing this for 32-bit kernels would bring > a performance penalty as a single read would require three 32-bit HPET > accesses). We tried that before and 64bit mode did not work on all tested platforms. Aside of that your patch is broken because it does not check whether HPET actually supports 64bit mode at all. The COUNT_SIZE_CAP bit is there for a reason. Thanks, tglx