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=-5.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 CD353C49EA2 for ; Thu, 17 Jun 2021 05:56:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A499261351 for ; Thu, 17 Jun 2021 05:56:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229671AbhFQF6x (ORCPT ); Thu, 17 Jun 2021 01:58:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:49340 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229515AbhFQF6w (ORCPT ); Thu, 17 Jun 2021 01:58:52 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id BFE4F61075; Thu, 17 Jun 2021 05:56:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1623909405; bh=vOtZNKgdXLXqvbCCw4+EXSMYJqOfs4O96QCwxuzPKbo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qNELfefjOAmF72RgUFSYDo4Z5fFYlxjRbHuar95j+JUZJM3ZgjfoCqhN7zHBh1NLu O5paI6p4ir9l5NxuT9uUonZlFMa504HLp2Gt6iLpKk+tjloFIl0Z6DA+5I2MLbsQOw 5SPL6v8y5Mhw6ZNQKl/x8pba97RTapGJ/iGkIKCs= Date: Thu, 17 Jun 2021 07:56:41 +0200 From: Greg KH To: Jing Zhang Cc: KVM , KVMARM , LinuxMIPS , KVMPPC , LinuxS390 , Linuxkselftest , Paolo Bonzini , Marc Zyngier , James Morse , Julien Thierry , Suzuki K Poulose , Will Deacon , Huacai Chen , Aleksandar Markovic , Thomas Bogendoerfer , Paul Mackerras , Christian Borntraeger , Janosch Frank , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Sean Christopherson , Vitaly Kuznetsov , Jim Mattson , Peter Shier , Oliver Upton , David Rientjes , Emanuele Giuseppe Esposito , David Matlack , Ricardo Koller , Krish Sadhukhan , Fuad Tabba Subject: Re: [PATCH v10 3/5] KVM: stats: Add documentation for binary statistics interface Message-ID: References: <20210617044146.2667540-1-jingzhangos@google.com> <20210617044146.2667540-4-jingzhangos@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210617044146.2667540-4-jingzhangos@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Thu, Jun 17, 2021 at 04:41:44AM +0000, Jing Zhang wrote: > + struct kvm_stats_desc { > + __u32 flags; > + __s16 exponent; > + __u16 size; > + __u32 offset; > + __u32 unused; > + char name[0]; > + }; > +The ``unused`` fields are reserved for future support for other types of > +statistics data, like log/linear histogram. you HAVE to set unused to 0 for now, otherwise userspace does not know it is unused, right? And then, really it is "used", so why not just say that now? It's tricky, but you have to get this right now otherwise you can never use it in the future. > +The ``name`` field points to the name string of the statistics data. The name It is not a pointer, it is the data itself. > +string starts at the end of ``struct kvm_stats_desc``. > +The maximum length (including trailing '\0') is indicated by ``name_size`` > +in ``struct kvm_stats_header``. I thought we were replacing [0] arrays with [], are you sure you should be declaring this as [0]? Same for all structures in this document (and code). thanks, greg k-h