From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [Qemu-devel] [PATCH 2/2] virtio-blk: disable write cache if not negotiated Date: Wed, 04 Jul 2012 14:21:19 +0200 Message-ID: <4FF4353F.8010809@redhat.com> References: <1341321642-24598-1-git-send-email-pbonzini@redhat.com> <1341321642-24598-3-git-send-email-pbonzini@redhat.com> <4FF2F87C.6010600@redhat.com> <4FF2F8DF.4020806@redhat.com> <4FF417F3.2090400@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Cc: anthony@codemonkey.ws, rusty@rustcorp.com.au, qemu-devel@nongnu.org, kvm@vger.kernel.org, mst@redhat.com To: Kevin Wolf Return-path: Received: from mail-wi0-f172.google.com ([209.85.212.172]:46085 "EHLO mail-wi0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750957Ab2GDMV2 (ORCPT ); Wed, 4 Jul 2012 08:21:28 -0400 Received: by wibhm11 with SMTP id hm11so5468575wib.1 for ; Wed, 04 Jul 2012 05:21:26 -0700 (PDT) In-Reply-To: <4FF417F3.2090400@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Il 04/07/2012 12:16, Kevin Wolf ha scritto: >> > Yes. It doesn't override cache=unsafe though. > When the guest doesn't support flushes, cache=writeback is equivalent to > cache=unsafe, so if you want the old behaviour back you can switch to > cache=unsafe without additional risks. > > We don't have a cache=directunsafe, though, so if you want to get the > old behaviour of cache=none back, you're out of luck. Not sure how > acceptable this is. If we want to fix this, let's take the occasion to split the parameters into cache=on/off (well, we have that already), flush=on/off, and a device-side wce=on/off. > Irrespective of this concern I've come to the conclusion that I agree > and we actually must enforce this for non-unsafe mode, and not doing it > is a bug. Thanks! Is that an Acked-by/Reviewed-by? :) Paolo