From patchwork Fri Nov 25 10:06:33 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Beulich X-Patchwork-Id: 9447135 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 97E306071C for ; Fri, 25 Nov 2016 10:07:25 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5EC04276D7 for ; Fri, 25 Nov 2016 10:07:25 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5370C28118; Fri, 25 Nov 2016 10:07:25 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id D7C6B276D7 for ; Fri, 25 Nov 2016 10:07:20 +0000 (UTC) Received: from localhost ([::1]:44997 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cADPc-00062F-4t for patchwork-qemu-devel@patchwork.kernel.org; Fri, 25 Nov 2016 05:07:20 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40198) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cADOy-0005x2-7i for qemu-devel@nongnu.org; Fri, 25 Nov 2016 05:06:45 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cADOt-0007Om-9a for qemu-devel@nongnu.org; Fri, 25 Nov 2016 05:06:40 -0500 Received: from prv-mh.provo.novell.com ([137.65.248.74]:51677) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cADOs-0007Nh-Vu for qemu-devel@nongnu.org; Fri, 25 Nov 2016 05:06:35 -0500 Received: from INET-PRV-MTA by prv-mh.provo.novell.com with Novell_GroupWise; Fri, 25 Nov 2016 03:06:33 -0700 Message-Id: <58381B39020000780012226E@prv-mh.provo.novell.com> X-Mailer: Novell GroupWise Internet Agent 14.2.1 Date: Fri, 25 Nov 2016 03:06:33 -0700 From: "Jan Beulich" To: References: <583819ED020000780012225B@prv-mh.provo.novell.com> In-Reply-To: <583819ED020000780012225B@prv-mh.provo.novell.com> Mime-Version: 1.0 Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [fuzzy] X-Received-From: 137.65.248.74 Subject: [Qemu-devel] [PATCH v2 2/3] xen: slightly simplify bufioreq handling X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: anthony.perard@citrix.com, xen-devel , Paul Durrant , Stefano Stabellini Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP There's no point setting fields always receiving the same value on each iteration, as handle_ioreq() doesn't alter them anyway. Set state and count once ahead of the loop, drop the redundant clearing of data_is_ptr, and avoid the meaningless setting of df altogether. Also avoid doing an unsigned long calculation of size when the field to be initialized is only 32 bits wide (and the shift value in the range 0...3). Signed-off-by: Jan Beulich Reviewed-by: Paul Durrant Reviewed-by: Stefano Stabellini --- a/xen-hvm.c +++ b/xen-hvm.c @@ -995,6 +995,8 @@ static int handle_buffered_iopage(XenIOS } memset(&req, 0x00, sizeof(req)); + req.state = STATE_IOREQ_READY; + req.count = 1; for (;;) { uint32_t rdptr = buf_page->read_pointer, wrptr; @@ -1009,15 +1011,11 @@ static int handle_buffered_iopage(XenIOS break; } buf_req = &buf_page->buf_ioreq[rdptr % IOREQ_BUFFER_SLOT_NUM]; - req.size = 1UL << buf_req->size; - req.count = 1; + req.size = 1U << buf_req->size; req.addr = buf_req->addr; req.data = buf_req->data; - req.state = STATE_IOREQ_READY; req.dir = buf_req->dir; - req.df = 1; req.type = buf_req->type; - req.data_is_ptr = 0; xen_rmb(); qw = (req.size == 8); if (qw) { @@ -1032,6 +1030,13 @@ static int handle_buffered_iopage(XenIOS handle_ioreq(state, &req); + /* Only req.data may get updated by handle_ioreq(), albeit even that + * should not happen as such data would never make it to the guest. + */ + assert(req.state == STATE_IOREQ_READY); + assert(req.count == 1); + assert(!req.data_is_ptr); + atomic_add(&buf_page->read_pointer, qw + 1); }