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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,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 8A113C43461 for ; Thu, 29 Apr 2021 16:06:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3E10E61469 for ; Thu, 29 Apr 2021 16:06:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240790AbhD2QHF (ORCPT ); Thu, 29 Apr 2021 12:07:05 -0400 Received: from foss.arm.com ([217.140.110.172]:54810 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233480AbhD2QHC (ORCPT ); Thu, 29 Apr 2021 12:07:02 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4E3DB101E; Thu, 29 Apr 2021 09:06:15 -0700 (PDT) Received: from [192.168.1.179] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9BDBB3F85F; Thu, 29 Apr 2021 09:06:12 -0700 (PDT) Subject: Re: [PATCH v11 5/6] KVM: arm64: ioctl to fetch/store tags in a guest To: Catalin Marinas Cc: Marc Zyngier , Will Deacon , James Morse , Julien Thierry , Suzuki K Poulose , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Dave Martin , Mark Rutland , Thomas Gleixner , qemu-devel@nongnu.org, Juan Quintela , "Dr. David Alan Gilbert" , Richard Henderson , Peter Maydell , Haibo Xu , Andrew Jones References: <20210416154309.22129-1-steven.price@arm.com> <20210416154309.22129-6-steven.price@arm.com> <20210427175844.GB17872@arm.com> From: Steven Price Message-ID: <340d35c2-46ed-35ea-43fa-e5cb64c27230@arm.com> Date: Thu, 29 Apr 2021 17:06:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <20210427175844.GB17872@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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]; >> +}; > > I know Marc asked for some reserved space in here but I'm not sure it's > the right place. And what's with the union of a 64-bit pointer and > 64-bit padding, it doesn't change any layout? Yes it's unnecessary here - habits die hard. This would ensure that the layout is the same for 32 bit and 64 bit. But it's irrelevant here as (a) we don't support 32 bit, and (b) flags has 64 bit alignment anyway. I'll drop the union (and 'padding'). > 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? > Or maybe I'm missing something, I haven't checked how other KVM ioctls > work. KVM ioctls seem to (sometimes) have some reserved space at the end of the structure for expansion without the ioctl number changing (since the structure size is encoded into the ioctl). Steve