Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755877Ab1EPUpx (ORCPT ); Mon, 16 May 2011 16:45:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:22515 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752861Ab1EPUpv (ORCPT ); Mon, 16 May 2011 16:45:51 -0400 Date: Mon, 16 May 2011 23:45:40 +0300 From: "Michael S. Tsirkin" To: Shirley Ma Cc: David Miller , Eric Dumazet , Avi Kivity , Arnd Bergmann , netdev@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V5 4/6 net-next] vhost: vhost TX zero-copy support Message-ID: <20110516204540.GD18148@redhat.com> References: <1305574484.3456.30.camel@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1305574484.3456.30.camel@localhost.localdomain> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 823 Lines: 18 > +/* Since we need to keep the order of used_idx as avail_idx, it's possible that > + * DMA done not in order in lower device driver for some reason. To prevent > + * used_idx out of order, upend_idx is used to track avail_idx order, done_idx > + * is used to track used_idx order. Once lower device DMA done, then upend_idx > + * can move to done_idx. Could you clarify this please? virtio explicitly allows out of order completion of requests. Does it simplify code that we try to keep used index updates in-order? Because if not, this is not really a requirement. -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/