From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: virtio scsi host draft specification, v3 Date: Wed, 29 Jun 2011 10:23:26 +0200 Message-ID: <4E0AE0FE.2090905@redhat.com> References: <4DEE2B15.4090809@redhat.com> <4DF21447.6090005@suse.de> <20110612075140.GB11941@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Hannes Reinecke , Linux Virtualization , Linux Kernel Mailing List , qemu-devel , Rusty Russell , Stefan Hajnoczi , Christoph Hellwig , "kvm@vger.kernel.org" To: "Michael S. Tsirkin" Return-path: Received: from mx1.redhat.com ([209.132.183.28]:8627 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753581Ab1F2IXm (ORCPT ); Wed, 29 Jun 2011 04:23:42 -0400 In-Reply-To: <20110612075140.GB11941@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 06/12/2011 09:51 AM, Michael S. Tsirkin wrote: >> > >> > If a device uses more than one queue it is the responsibility of the >> > device to ensure strict request ordering. > Maybe I misunderstand - how can this be the responsibility of > the device if the device does not get the information about > the original ordering of the requests? > > For example, if the driver is crazy enough to put > all write requests on one queue and all barriers > on another one, how is the device supposed to ensure > ordering? I agree here, in fact I misread Hannes's comment as "if a driver uses more than one queue it is responsibility of the driver to ensure strict request ordering". If you send requests to different queues, you know that those requests are independent. I don't think anything else is feasible in the virtio framework. Paolo