From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zachary Amsden Subject: Re: [PATCH 1/5] Add a global synchronization point for pvclock Date: Fri, 23 Apr 2010 11:41:18 -1000 Message-ID: <4BD213FE.2000800@redhat.com> References: <1271675100.1674.818.camel@laptop> <4BCC3A3E.9070909@redhat.com> <20100419142158.GD14158@mothafucka.localdomain> <4BCC69D5.3050209@redhat.com> <1271688411.1488.248.camel@laptop> <4BCC8246.9040202@goop.org> <4BCD748E.7080007@redhat.com> <4BCDF12C.1020702@goop.org> <4BCDF85C.3000004@redhat.com> <4BCE0399.2010708@goop.org> <20100422131113.GA3364@mothafucka.localdomain> <4BD0FB92.4060301@redhat.com> <4BD169B5.4000409@redhat.com> <4BD211B9.5080707@redhat.com> <4BD212BF.60707@goop.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Avi Kivity , Glauber Costa , Peter Zijlstra , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Marcelo Tosatti To: Jeremy Fitzhardinge Return-path: In-Reply-To: <4BD212BF.60707@goop.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 04/23/2010 11:35 AM, Jeremy Fitzhardinge wrote: > On 04/23/2010 02:31 PM, Zachary Amsden wrote: > >> Does lfence / mfence actually serialize? I thought there was some >> great confusion about that not being the case on all AMD processors, >> and possibly not at all on Intel. >> >> A trap, however is a great way to serialize. >> >> I think, there is no serializing instruction which can be used from >> userspace which does not trap, at least, I don't know one off the top >> of my head. >> > rsm is not technically privileged... but not quite usable from usermode ;) > rsm under hardware virtualization makes my head hurt