Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758840Ab0FPOEZ (ORCPT ); Wed, 16 Jun 2010 10:04:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:1029 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754072Ab0FPOEY (ORCPT ); Wed, 16 Jun 2010 10:04:24 -0400 Date: Wed, 16 Jun 2010 11:03:31 -0300 From: Glauber Costa To: Jason Wang Cc: Zachary Amsden , Avi Kivity , mtosatti@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, john stultz , Thomas Gleixner Subject: Re: [PATCH 12/17] Add helper function get_kernel_ns Message-ID: <20100616140331.GN19104@mothafucka.localdomain> References: <1276587259-32319-1-git-send-email-zamsden@redhat.com> <1276587259-32319-13-git-send-email-zamsden@redhat.com> <4C173CC3.8000506@redhat.com> <4C17EAA5.90009@redhat.com> <4C18877E.9070605@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4C18877E.9070605@redhat.com> X-ChuckNorris: True User-Agent: Jack Bauer Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2282 Lines: 67 On Wed, Jun 16, 2010 at 04:12:46PM +0800, Jason Wang wrote: > Zachary Amsden wrote: > > On 06/14/2010 10:41 PM, Avi Kivity wrote: > > > >> On 06/15/2010 10:34 AM, Zachary Amsden wrote: > >> > >>> Add a helper function for the multiple places this is used. Note > >>> that it > >>> must not be called in preemptible context, as that would mean the kernel > >>> could enter software suspend state, which would cause non-atomic > >>> operation > >>> of the monotonic_to_bootbased computation. > >>> > >>> Open question: should the KVM_SET_CLOCK / KVM_GET_CLOCK ioctls use this > >>> as well? Currently, they are not bootbased (but perhaps should be). > >>> > >>> Signed-off-by: Zachary Amsden > >>> --- > >>> arch/x86/kvm/x86.c | 26 +++++++++++++------------- > >>> 1 files changed, 13 insertions(+), 13 deletions(-) > >>> > >>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > >>> index 703ea43..15c7317 100644 > >>> --- a/arch/x86/kvm/x86.c > >>> +++ b/arch/x86/kvm/x86.c > >>> @@ -915,6 +915,16 @@ static void kvm_get_time_scale(uint32_t > >>> scaled_khz, uint32_t base_khz, > >>> __func__, base_khz, scaled_khz, shift, *pmultiplier); > >>> } > >>> > >>> +static inline u64 get_kernel_ns(void) > >>> +{ > >>> + struct timespec ts; > >>> + > >>> + WARN_ON(preemptible()); > >>> + ktime_get_ts(&ts); > >>> + monotonic_to_bootbased(&ts); > >>> + return timespec_to_ns(&ts); > >>> +} > >>> + > >>> static DEFINE_PER_CPU(unsigned long, cpu_tsc_khz); > >>> > >>> > >> Isn't something like this a candidate for the time infrastructure? > >> > >> > > > > Should it be? It certainly seems reasonable. > > > > > > Also, should we be using it for the cases KVM_GET_CLOCK / > > KVM_SET_CLOCK? It seems global kvmclock_offset for the VM ignores the > > bootbased conversion. > > > > > Yes we should. indeed. Also shows the importance of doing it in a central place. Have we had an acessor like that before, we would probably not have made this mistake. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/