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=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 E6A2BC433E0 for ; Wed, 13 Jan 2021 13:18:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9D6C323434 for ; Wed, 13 Jan 2021 13:18:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725823AbhAMNST (ORCPT ); Wed, 13 Jan 2021 08:18:19 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:58335 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725801AbhAMNST (ORCPT ); Wed, 13 Jan 2021 08:18:19 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1610543812; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3rGhWToIyZPL0OktEK6wCt3StrIOhYPirvwNLhTW5lw=; b=QZCleen23nVQ/oKL6Ngvbg3SNZLGWq4eS1bvZhTV1i/1qPpJHQnDRrFRidWVOB6wm/LcGh 2VxgtTIN4yu2UZNipvE1xMyYgSbN4/xTIzRbZJ8nZyABQ9PWK4nwZYpQMtZyAa9oD45fPo 1vtA0CvZnxe9kpbv10wE+qwLq6jEL38= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-37-yfgsj-0HNYirYlcpheAqWg-1; Wed, 13 Jan 2021 08:16:48 -0500 X-MC-Unique: yfgsj-0HNYirYlcpheAqWg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 934F3107ACF9; Wed, 13 Jan 2021 13:16:47 +0000 (UTC) Received: from thuth.remote.csb (ovpn-112-122.ams2.redhat.com [10.36.112.122]) by smtp.corp.redhat.com (Postfix) with ESMTP id 717A65D9DC; Wed, 13 Jan 2021 13:16:43 +0000 (UTC) Subject: Re: [kvm-unit-tests PATCH v4 9/9] s390x: sclp: Add CPU entry offset comment To: David Hildenbrand , Janosch Frank , kvm@vger.kernel.org Cc: borntraeger@de.ibm.com, imbrenda@linux.ibm.com, cohuck@redhat.com, linux-s390@vger.kernel.org References: <20210112132054.49756-1-frankja@linux.ibm.com> <20210112132054.49756-10-frankja@linux.ibm.com> <6f93c964-9606-246c-7266-85044803e49b@redhat.com> From: Thomas Huth Message-ID: Date: Wed, 13 Jan 2021 14:16:42 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <6f93c964-9606-246c-7266-85044803e49b@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 13/01/2021 11.25, David Hildenbrand wrote: > On 12.01.21 14:20, Janosch Frank wrote: >> Let's make it clear that there is something at the end of the >> struct. The exact offset is reported by the cpu_offset member. >> >> Signed-off-by: Janosch Frank >> --- >> lib/s390x/sclp.h | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h >> index dccbaa8..395895f 100644 >> --- a/lib/s390x/sclp.h >> +++ b/lib/s390x/sclp.h >> @@ -134,7 +134,10 @@ typedef struct ReadInfo { >> uint8_t reserved7[134 - 128]; >> uint8_t byte_134_diag318 : 1; >> uint8_t : 7; >> - struct CPUEntry entries[0]; >> + /* >> + * The cpu entries follow, they start at the offset specified >> + * in offset_cpu. >> + */ > > I mean, that's just best practice. At least when I spot "[0];" and the > end of a struct, I know what's happening. > > No strong opinion about the comment, I wouldn't need it to understand it. The problem is that the "CPUEntry" entries either might be at this location, or later, so the entries[0] can be misleading. You always have to go via the offset_cpu field to find the right location. Thomas