From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 52896C10DCE for ; Tue, 10 Mar 2020 06:22:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 252E12464B for ; Tue, 10 Mar 2020 06:22:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726325AbgCJGWC (ORCPT ); Tue, 10 Mar 2020 02:22:02 -0400 Received: from mx2.suse.de ([195.135.220.15]:38100 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726252AbgCJGWB (ORCPT ); Tue, 10 Mar 2020 02:22:01 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id CC0BBB35A; Tue, 10 Mar 2020 06:21:59 +0000 (UTC) Subject: Re: [PATCH v2] xen: Use evtchn_type_t as a type for event channels To: Yan Yankovskyi , Boris Ostrovsky Cc: Jan Beulich , Stefano Stabellini , xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org References: <20200307134322.GA27756@kbp1-lhp-F74019> <20200308131944.GA18740@kbp1-lhp-F74019> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: Date: Tue, 10 Mar 2020 07:21:58 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200308131944.GA18740@kbp1-lhp-F74019> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08.03.20 14:19, Yan Yankovskyi wrote: > On Sat, Mar 07, 2020 at 02:41:44PM -0500, Boris Ostrovsky wrote: >> >> >> On 3/7/20 8:43 AM, Yan Yankovskyi wrote: >>> Make event channel functions pass event channel port using >>> evtchn_port_t type. It eliminates signed <-> unsigned conversion. >>> >> >> >>> static int find_virq(unsigned int virq, unsigned int cpu) >>> { >>> struct evtchn_status status; >>> - int port, rc = -ENOENT; >>> + evtchn_port_t port; >>> + int rc = -ENOENT; >>> >>> memset(&status, 0, sizeof(status)); >>> for (port = 0; port < xen_evtchn_max_channels(); port++) { >>> @@ -962,7 +963,8 @@ EXPORT_SYMBOL_GPL(xen_evtchn_nr_channels); >>> int bind_virq_to_irq(unsigned int virq, unsigned int cpu, bool percpu) >>> { >>> struct evtchn_bind_virq bind_virq; >>> - int evtchn, irq, ret; >>> + evtchn_port_t evtchn = xen_evtchn_max_channels(); >>> + int irq, ret; >>> >>> mutex_lock(&irq_mapping_update_lock); >>> >>> @@ -990,7 +992,6 @@ int bind_virq_to_irq(unsigned int virq, unsigned int cpu, bool percpu) >>> if (ret == -EEXIST) >>> ret = find_virq(virq, cpu); >>> BUG_ON(ret < 0); >>> - evtchn = ret; >> >> >> This looks suspicious. What would you be passing to >> xen_irq_info_virq_setup() below? > > Right, this line should be preserved. > >> I also think that, given that this patch is trying to get types in >> order, find_virq() will need more changes: it is supposed to return >> evtchn_port_t. But then it also wants to return a (signed) error. > > As we don't care which error we got during find_virq call, we can just > return 0 in case of error, and port number otherwise. Port 0 is never > valid, so this approach can work for the other functions as well. > On the other hand, passing port using pointer and returning actual > error message, as it's done in xenbus_alloc_evtchn(), sounds like a > better approach overall. What do you think? You can use the same approach as Xen tools do and define something like: typedef int evtchn_port_or_error_t; Juergen