From mboxrd@z Thu Jan 1 00:00:00 1970 From: Radim =?utf-8?B?S3LEjW3DocWZ?= Subject: Re: KVM: x86: workaround SuSE's 2.6.16 pvclock vs masterclock issue Date: Wed, 21 Jan 2015 15:09:27 +0100 Message-ID: <20150121140926.GA9085@potion.brq.redhat.com> References: <20150120175452.GA32680@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm-devel , Paolo Bonzini To: Marcelo Tosatti Return-path: Received: from mx1.redhat.com ([209.132.183.28]:59498 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751546AbbAUOJb (ORCPT ); Wed, 21 Jan 2015 09:09:31 -0500 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id t0LE9UBA006757 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL) for ; Wed, 21 Jan 2015 09:09:30 -0500 Content-Disposition: inline In-Reply-To: <20150120175452.GA32680@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: 2015-01-20 15:54-0200, Marcelo Tosatti: > SuSE's 2.6.16 kernel fails to boot if the delta between tsc_timestamp > and rdtsc is larger than a given threshold: [...] > Disable masterclock support (which increases said delta) in case the > boot vcpu does not use MSR_KVM_SYSTEM_TIME_NEW. Why do we care about 2.6.16 bugs in upstream KVM? The code to benefit tradeoff of this patch seems bad to me ... MSR_KVM_SYSTEM_TIME is deprecated -- we could remove it now, with MSR_KVM_WALL_CLOCK (after hiding KVM_FEATURE_CLOCKSOURCE) if we want to support old guests.