From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:56049) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1StLZ3-0002Kb-Lj for qemu-devel@nongnu.org; Mon, 23 Jul 2012 12:32:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1StLYz-0004sW-MI for qemu-devel@nongnu.org; Mon, 23 Jul 2012 12:32:57 -0400 Received: from mail-pb0-f45.google.com ([209.85.160.45]:65460) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1StLYz-0004sH-FX for qemu-devel@nongnu.org; Mon, 23 Jul 2012 12:32:53 -0400 Received: by pbbro12 with SMTP id ro12so10980753pbb.4 for ; Mon, 23 Jul 2012 09:32:52 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <500D7CA6.5090901@redhat.com> Date: Mon, 23 Jul 2012 18:32:38 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1341321642-24598-1-git-send-email-pbonzini@redhat.com> In-Reply-To: <1341321642-24598-1-git-send-email-pbonzini@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: , Cc: kwolf@redhat.com, kvm@vger.kernel.org, mst@redhat.com, rusty@rustcorp.com.au, qemu-devel@nongnu.org, anthony@codemonkey.ws 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? Paolo