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=-10.8 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 CD09BC07E94 for ; Fri, 4 Jun 2021 11:16:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B4279613FF for ; Fri, 4 Jun 2021 11:16:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230150AbhFDLRr (ORCPT ); Fri, 4 Jun 2021 07:17:47 -0400 Received: from foss.arm.com ([217.140.110.172]:36474 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229962AbhFDLRq (ORCPT ); Fri, 4 Jun 2021 07:17:46 -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 168702B; Fri, 4 Jun 2021 04:16:00 -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 766343F73D; Fri, 4 Jun 2021 04:15:57 -0700 (PDT) Subject: Re: [PATCH v13 7/8] 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: <20210524104513.13258-1-steven.price@arm.com> <20210524104513.13258-8-steven.price@arm.com> <20210603171336.GH20338@arm.com> From: Steven Price Message-ID: <02c7682e-5fb6-29eb-9105-02e3521756a2@arm.com> Date: Fri, 4 Jun 2021 12:15:56 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210603171336.GH20338@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/06/2021 18:13, Catalin Marinas wrote: > On Mon, May 24, 2021 at 11:45:12AM +0100, Steven Price wrote: >> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h >> index 24223adae150..b3edde68bc3e 100644 >> --- a/arch/arm64/include/uapi/asm/kvm.h >> +++ b/arch/arm64/include/uapi/asm/kvm.h >> @@ -184,6 +184,17 @@ struct kvm_vcpu_events { >> __u32 reserved[12]; >> }; >> >> +struct kvm_arm_copy_mte_tags { >> + __u64 guest_ipa; >> + __u64 length; >> + void __user *addr; >> + __u64 flags; >> + __u64 reserved[2]; >> +}; >> + >> +#define KVM_ARM_TAGS_TO_GUEST 0 >> +#define KVM_ARM_TAGS_FROM_GUEST 1 >> + >> /* If you need to interpret the index values, here is the key: */ >> #define KVM_REG_ARM_COPROC_MASK 0x000000000FFF0000 >> #define KVM_REG_ARM_COPROC_SHIFT 16 >> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c >> index e89a5e275e25..baa33359e477 100644 >> --- a/arch/arm64/kvm/arm.c >> +++ b/arch/arm64/kvm/arm.c >> @@ -1345,6 +1345,13 @@ long kvm_arch_vm_ioctl(struct file *filp, >> >> return 0; >> } >> + case KVM_ARM_MTE_COPY_TAGS: { >> + struct kvm_arm_copy_mte_tags copy_tags; >> + >> + if (copy_from_user(©_tags, argp, sizeof(copy_tags))) >> + return -EFAULT; >> + return kvm_vm_ioctl_mte_copy_tags(kvm, ©_tags); >> + } > > I wonder whether we need an update of the user structure following a > fault, like how much was copied etc. In case of an error, some tags were > copied and the VMM may want to skip the page before continuing. But here > there's no such information provided. > > On the ptrace interface, we return 0 on the syscall if any bytes were > copied and update iov_len to such number. Maybe you want to still return > an error here but updating copy_tags.length would be nice (and, of > course, a copy_to_user() back). > Good idea - as you suggest I'll make it update length with the number of bytes not processed. Although in general I think we're expecting the VMM to know where the memory is so this is more of a programming error - but could still be useful for debugging. Thanks, Steve