From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MlPHt-0007i5-EJ for qemu-devel@nongnu.org; Wed, 09 Sep 2009 11:40:49 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MlPHo-0007ht-JG for qemu-devel@nongnu.org; Wed, 09 Sep 2009 11:40:48 -0400 Received: from [199.232.76.173] (port=58191 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MlPHo-0007hq-Ex for qemu-devel@nongnu.org; Wed, 09 Sep 2009 11:40:44 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:44034) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1MlPHo-0007Nx-3t for qemu-devel@nongnu.org; Wed, 09 Sep 2009 11:40:44 -0400 Received: from d03relay04.boulder.ibm.com (d03relay04.boulder.ibm.com [9.17.195.106]) by e32.co.us.ibm.com (8.14.3/8.13.1) with ESMTP id n89FaC3g003051 for ; Wed, 9 Sep 2009 09:36:12 -0600 Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by d03relay04.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id n89FeSFT042554 for ; Wed, 9 Sep 2009 09:40:32 -0600 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id n89FeRrb002906 for ; Wed, 9 Sep 2009 09:40:28 -0600 Message-ID: <4AA7CC66.5060008@us.ibm.com> Date: Wed, 09 Sep 2009 10:40:22 -0500 From: Anthony Liguori MIME-Version: 1.0 References: <20090909151111.26816.49862.stgit@mchn012c.ww002.siemens.net> In-Reply-To: <20090909151111.26816.49862.stgit@mchn012c.ww002.siemens.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: [PATCH 0/5] Refactor and enhance RTC configuration List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: Blue Swirl , Glauber Costa , Dor Laor , qemu-devel@nongnu.org Jan Kiszka wrote: > The aim of this series is to allow using the emulated PC RTC (MC146818) > as a reliable time source for guests. This is particularly useful if the > host runs NTP or has otherwise access to an accurate clock while the > guest has not (no network, impossible to add an NTP implementation > etc.). > > To achieve this, the command line switch -rtc is introduced. It takes > the option 'clock' to switch between the currently used base ('vm') and > the new QEMU_CLOCK_HOST ('host'). At this chance, -rtc is also used to > deprecate all the other RTC-related stand-alone switches. > > First tests indicate that this approach works as expected and could > increase the usefulness of the virtual RTC enormously. However, there > might be pitfalls I've missed so far. Feedback would be welcome! > You get most of this pretty cheaply with qdev conversion. If you give the rtc a default id, you can tweak all of the properties with the -set command line option. It also provides a mechanism to change the default properties between machine types/versions which is ideal as we can introduce a kvm-specific machine type where we enable some of these things by default. -- Regards, Anthony Liguori