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,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 89116C07E94 for ; Fri, 4 Jun 2021 11:42:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6F49D613FF for ; Fri, 4 Jun 2021 11:42:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230162AbhFDLo0 (ORCPT ); Fri, 4 Jun 2021 07:44:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:39490 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230010AbhFDLoZ (ORCPT ); Fri, 4 Jun 2021 07:44:25 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 89B72613E9; Fri, 4 Jun 2021 11:42:36 +0000 (UTC) Date: Fri, 4 Jun 2021 12:42:34 +0100 From: Catalin Marinas To: Steven Price 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 Subject: Re: [PATCH v13 7/8] KVM: arm64: ioctl to fetch/store tags in a guest Message-ID: <20210604114233.GE31173@arm.com> References: <20210524104513.13258-1-steven.price@arm.com> <20210524104513.13258-8-steven.price@arm.com> <20210603171336.GH20338@arm.com> <02c7682e-5fb6-29eb-9105-02e3521756a2@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <02c7682e-5fb6-29eb-9105-02e3521756a2@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 04, 2021 at 12:15:56PM +0100, Steven Price wrote: > 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. Or update it to the number of bytes copied to be consistent with ptrace()'s iov.len. On success, the structure is effectively left unchanged. -- Catalin