From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:35048) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SwbjY-0007CM-SZ for qemu-devel@nongnu.org; Wed, 01 Aug 2012 12:25:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SwbjT-0007ha-5h for qemu-devel@nongnu.org; Wed, 01 Aug 2012 12:25:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41447) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SwbjS-0007hW-U3 for qemu-devel@nongnu.org; Wed, 01 Aug 2012 12:25:11 -0400 Message-ID: <50195861.2080601@redhat.com> Date: Wed, 01 Aug 2012 18:25:05 +0200 From: Kevin Wolf MIME-Version: 1.0 References: <1341321642-24598-1-git-send-email-pbonzini@redhat.com> <500D7CA6.5090901@redhat.com> <501950C0.4050201@redhat.com> In-Reply-To: <501950C0.4050201@redhat.com> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [QEMU PATCH 0/2] virtio-blk: writeback cache enable improvements List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: anthony@codemonkey.ws, rusty@rustcorp.com.au, qemu-devel@nongnu.org, kvm@vger.kernel.org, mst@redhat.com Am 01.08.2012 17:52, schrieb Paolo Bonzini: > Il 23/07/2012 18:32, Paolo Bonzini ha scritto: >> Il 03/07/2012 15:20, Paolo Bonzini ha scritto: >>>> These patches let virtio-blk use the new support for toggling the cache >>>> mode between writethrough and writeback. >>>> >>>> The first patch introduces a new feature bit and configuration field to >>>> do this. The second patch disables writeback caching for guests that do >>>> not negotiate VIRTIO_BLK_F_WCACHE (meaning that they cannot send flush >>>> requests), so that limited or older guests are now safe wrt power losses. >>>> VIRTIO_BLK_F_FLUSH has been introduced in Linux 2.6.32 (in 2009) and was >>>> backported to RHEL/CentOS 5.6 (in 2010). >>>> >>>> The Windows drivers (which work by emulating SCSI on top of virtio-blk) >>>> have bugs in this area, which I reported on the Red Hat Bugzilla as >>>> bugs 837321 and 837324. With these patches they will suffer a >>>> performance hit but gain correctness. >>>> >>>> Paolo Bonzini (2): >>>> virtio-blk: support VIRTIO_BLK_F_CONFIG_WCE >>>> virtio-blk: disable write cache if not negotiated >> Ping - Anthony, mst? > > Ping^2, so we can switch writethrough->writeback in 1.2. Speak now or forever hold your peace. If there are no more comments until Friday, I'll just apply it. Kevin