From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:53440) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SwbE6-00072e-5c for qemu-devel@nongnu.org; Wed, 01 Aug 2012 11:52:47 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SwbE1-0005le-U1 for qemu-devel@nongnu.org; Wed, 01 Aug 2012 11:52:46 -0400 Received: from mail-yx0-f173.google.com ([209.85.213.173]:51196) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SwbE1-0005lY-Pr for qemu-devel@nongnu.org; Wed, 01 Aug 2012 11:52:41 -0400 Received: by yenl1 with SMTP id l1so7246903yen.4 for ; Wed, 01 Aug 2012 08:52:41 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <501950C0.4050201@redhat.com> Date: Wed, 01 Aug 2012 17:52:32 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1341321642-24598-1-git-send-email-pbonzini@redhat.com> <500D7CA6.5090901@redhat.com> In-Reply-To: <500D7CA6.5090901@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: qemu-devel@nongnu.org Cc: kwolf@redhat.com, rusty@rustcorp.com.au, anthony@codemonkey.ws, kvm@vger.kernel.org, mst@redhat.com 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. Paolo