From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH uq/master] kvm: i8254: Fix conversion of in-kernel to userspace state Date: Mon, 11 Jun 2012 13:07:14 +0300 Message-ID: <4FD5C352.4000004@redhat.com> References: <4FCF691A.10502@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , kvm , qemu-devel , qemu-stable To: Jan Kiszka Return-path: Received: from mx1.redhat.com ([209.132.183.28]:41947 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752785Ab2FKKHX (ORCPT ); Mon, 11 Jun 2012 06:07:23 -0400 In-Reply-To: <4FCF691A.10502@siemens.com> Sender: kvm-owner@vger.kernel.org List-ID: On 06/06/2012 05:28 PM, Jan Kiszka wrote: > Due to a offset between the clock used to generate the in-kernel > count_load_time (CLOCK_MONOTONIC) and the clock used for processing this > in userspace (vm_clock), reading back the output of PIT channel 2 via > port 0x61 was broken. One use cases that suffered from it was the CPU > frequency calibration of SeaBIOS, which also affected IDE/AHCI timeouts. > > This fixes it by calibrating the offset between both clocks on > kvm_pit_get and adjusting the kernel value before saving it in the > userspace state. As the calibration only works while the vm_clock is > running, we cache the in-kernel state across stopped phases. Applied, thanks. > + clock_offset = LLONG_MAX; INT64_MAX would me more strictly correct, but in practice it makes no difference. -- error compiling committee.c: too many arguments to function