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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=unavailable 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 71AC3C433B4 for ; Tue, 4 May 2021 17:48:15 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1BDF3613C6 for ; Tue, 4 May 2021 17:48:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1BDF3613C6 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:39472 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ldz9a-0002Q3-5n for qemu-devel@archiver.kernel.org; Tue, 04 May 2021 13:48:14 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52382) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ldz6S-00013a-M8 for qemu-devel@nongnu.org; Tue, 04 May 2021 13:45:02 -0400 Received: from mail.kernel.org ([198.145.29.99]:56990) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ldz6F-00078G-Im for qemu-devel@nongnu.org; Tue, 04 May 2021 13:44:56 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9249C61166; Tue, 4 May 2021 17:44:39 +0000 (UTC) Date: Tue, 4 May 2021 18:44:37 +0100 From: Catalin Marinas To: Steven Price Subject: Re: [PATCH v11 5/6] KVM: arm64: ioctl to fetch/store tags in a guest Message-ID: References: <20210416154309.22129-1-steven.price@arm.com> <20210416154309.22129-6-steven.price@arm.com> <20210427175844.GB17872@arm.com> <340d35c2-46ed-35ea-43fa-e5cb64c27230@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <340d35c2-46ed-35ea-43fa-e5cb64c27230@arm.com> Received-SPF: pass client-ip=198.145.29.99; envelope-from=cmarinas@kernel.org; helo=mail.kernel.org X-Spam_score_int: -66 X-Spam_score: -6.7 X-Spam_bar: ------ X-Spam_report: (-6.7 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.248, RCVD_IN_DNSWL_HI=-5, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Peter Maydell , "Dr. David Alan Gilbert" , Andrew Jones , Haibo Xu , Suzuki K Poulose , qemu-devel@nongnu.org, Marc Zyngier , Juan Quintela , Richard Henderson , linux-kernel@vger.kernel.org, Dave Martin , James Morse , linux-arm-kernel@lists.infradead.org, Thomas Gleixner , Will Deacon , kvmarm@lists.cs.columbia.edu, Julien Thierry Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Apr 29, 2021 at 05:06:07PM +0100, Steven Price wrote: > On 27/04/2021 18:58, Catalin Marinas wrote: > > On Fri, Apr 16, 2021 at 04:43:08PM +0100, Steven Price wrote: > > > diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h > > > index 24223adae150..2b85a047c37d 100644 > > > --- a/arch/arm64/include/uapi/asm/kvm.h > > > +++ b/arch/arm64/include/uapi/asm/kvm.h > > > @@ -184,6 +184,20 @@ struct kvm_vcpu_events { > > > __u32 reserved[12]; > > > }; > > > +struct kvm_arm_copy_mte_tags { > > > + __u64 guest_ipa; > > > + __u64 length; > > > + union { > > > + void __user *addr; > > > + __u64 padding; > > > + }; > > > + __u64 flags; > > > + __u64 reserved[2]; > > > +}; [...] > > Maybe add the two reserved > > values to the union in case we want to store something else in the > > future. > > I'm not sure what you mean here. What would the reserved fields be unioned > with? And surely they are no longer reserved in that case? In case you want to keep the structure size the same for future expansion and the expansion only happens via the union, you'd add some padding in there just in case. We do this for struct siginfo with an _si_pad[] array in the union. -- Catalin