From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56110) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1c3poh-000711-5Z for qemu-devel@nongnu.org; Mon, 07 Nov 2016 14:42:52 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1c3poc-0001ZP-At for qemu-devel@nongnu.org; Mon, 07 Nov 2016 14:42:51 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47028) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1c3poc-0001Z2-4E for qemu-devel@nongnu.org; Mon, 07 Nov 2016 14:42:46 -0500 Date: Mon, 7 Nov 2016 17:31:03 -0200 From: Marcelo Tosatti Message-ID: <20161107193100.GA28327@amt.cnet> References: <20161104094322.GA16930@amt.cnet> <20161104152522.GC5388@potion> <1c69a083-eef0-8fa0-0e74-5a4e25a066a0@redhat.com> <20161104154827.GD5388@potion> <1217f6ce-8143-8d0e-97f6-470926438992@redhat.com> <20161104171605.GE5388@potion> <20161107143148.GA2199@rkaganb.sw.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20161107143148.GA2199@rkaganb.sw.ru> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [QEMU PATCH] kvmclock: advance clock by time window between vm_stop and pre_save List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Roman Kagan , Radim =?utf-8?B?S3LEjW3DocWZ?= , Paolo Bonzini , kvm@vger.kernel.org, qemu-devel , "Dr. David Alan Gilbert" , Juan Quintela , Eduardo Habkost On Mon, Nov 07, 2016 at 05:31:49PM +0300, Roman Kagan wrote: > On Fri, Nov 04, 2016 at 06:16:06PM +0100, Radim Kr=C4=8Dm=C3=A1=C5=99 w= rote: > > 2016-11-04 16:57+0100, Paolo Bonzini: > > > On 04/11/2016 16:48, Radim Kr=C4=8Dm=C3=A1=C5=99 wrote: > > >> 2016-11-04 16:33+0100, Paolo Bonzini: > > >>> On 04/11/2016 16:25, Radim Kr=C4=8Dm=C3=A1=C5=99 wrote: > > >>>>>> =20 > > >>>>>> + if (s->advance_clock && s->clock + s->advance_clock >= s->clock) { > > >>>>>> + s->clock +=3D s->advance_clock; > > >>>>>> + s->advance_clock =3D 0; > > >>>>>> + } > > >>>> Can't the advance_clock added to the migrated KVMClockState inst= ead of > > >>>> passing it as another parameter? > > >>>> > > >>>> (It is sad that we can't just query KVMClockState in kvmclock_pr= e_save > > >>>> because of the Linux bug.) > > >>> > > >>> What Linux bug? The one that makes us use kvmclock_current_nsec? > > >>=20 > > >> No, the one that forced Marcelo to add the 10 minute limit to the > > >> advance_clock. We wouldn't need this advance_clock hack if we cou= ld > > >> just call KVM_GET_CLOCK like we did before 00f4d64ee76e ("kvmclock= : > > >> clock should count only if vm is running"). > > >=20 > > > There are two cases: > > >=20 > > > - migrating a paused guest > > >=20 > > > - pausing at the end of migration > > >=20 > > > In the first case, kvmclock_vm_state_change's !running branch will = see > > > state =3D=3D RUN_STATE_FINISH_MIGRATE && s->clock_valid. In the se= cond > > > case, it will see state =3D=3D RUN_STATE_FINISH_MIGRATE && !s->cloc= k_valid. > >=20 > > I lift my case, marcelo's said that stopping the time is a feature ..= . > > (*kittens die*) >=20 > Sorry to chime in in the middle of the thread, but I wonder how happy > the guests are with this behavior. Intuitively pausing or snapshotting > feels like closing the lid of a laptop, so every time I see the guest > waking up in the past after a pause I get confused. It may also be > unexpected by Windows guests who never had this overflow problem but > now, being tied up with kvmclock, have to stop the time while in pause, > too. >=20 > Roman. Waking up should be using guest-set-time QGA API:=20 http://bugzilla.redhat.com/show_bug.cgi?id=3D1102411 Check "virsh domtime".