From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:35241) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TCBgH-000231-U8 for qemu-devel@nongnu.org; Thu, 13 Sep 2012 11:50:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TCBgB-0005J6-VN for qemu-devel@nongnu.org; Thu, 13 Sep 2012 11:50:17 -0400 Received: from mail-ob0-f173.google.com ([209.85.214.173]:55633) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TCBgB-0005Hw-Rw for qemu-devel@nongnu.org; Thu, 13 Sep 2012 11:50:11 -0400 Received: by obbta14 with SMTP id ta14so4381803obb.4 for ; Thu, 13 Sep 2012 08:50:10 -0700 (PDT) From: Anthony Liguori In-Reply-To: <5051FE85.6070904@redhat.com> References: <87pq5r5otp.fsf@codemonkey.ws> <20120912151549.GT20907@redhat.com> <87y5kfrtne.fsf@codemonkey.ws> <20120913104940.GA20907@redhat.com> <5051DC20.4090204@redhat.com> <20120913132804.GO7767@redhat.com> <87r4q6xbiy.fsf@codemonkey.ws> <20120913142228.GK20907@redhat.com> <5051EF0D.4070109@redhat.com> <5051F0CB.9040303@redhat.com> <5051FE85.6070904@redhat.com> Date: Thu, 13 Sep 2012 10:50:06 -0500 Message-ID: <87har1orbl.fsf@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: Re: [Qemu-devel] Rethinking missed tick catchup List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Avi Kivity , Eric Blake Cc: Michael Roth , Gleb Natapov , Jan Kiszka , qemu-devel@nongnu.org, Luiz Capitulino , Paolo Bonzini Avi Kivity writes: > On 09/13/2012 05:42 PM, Eric Blake wrote: >> On 09/13/2012 08:34 AM, Avi Kivity wrote: >>> On 09/13/2012 05:22 PM, Gleb Natapov wrote: >>>>> >>>>> It's much easier for us to call into qemu-ga to do the time correction >>>>> whenever this event occurs than to try and have libvirt figure out when >>>>> it's necessary. >>> >>>> And if guest does not have qemu-ga what is better inject interrupts like >>>> crazy for next 2 minutes or leave guest with incorrect time? >>> >>> We can try to S3 and resume the guest. The guest will assume that it >>> has slept for an unknown amount of time and resync from the RTC. >> >> Just restating to make sure I'm clear: you are proposing that after host >> suspend and host wakeup, _then_ qemu asks the guest to go into S3 >> followed by an immediate resume. During the time that the guest goes >> into S3, its clock is way off; but then the immediate resume will be the >> necessary kick to the guest to resync, and at that point, the guest can >> assume that it has been off since the host originally suspended (rather >> than the instant window where qemu actually bounced S3 after the host >> had already resumed). > > Correct. In theory we can shut down networking while this is happening > so the guest can't tell it's in a time machine. > >> >>> This may not work for really old server oriented guests. >> >> S3 requires guest cooperation, period. But so does qemu-ga. It's >> better than nothing, and we can't get perfection without guest cooperation. > > qemu-ga requires either an admin/tool to install qemu-ga, or for qemu-ga > to be preinstalled by the OS vendor. S3 requires S3 support to be > provided by the host vendor, and for it to be functional. A > significantly easier bar to clear. We can easily generate an ISO that includes a pre-built version of qemu-ga. Plus, there's a whole variety of other features enabled once we can assume qemu-ga is available. It's worth solving that problem. Regards, Anthony Liguori > > > -- > error compiling committee.c: too many arguments to function