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=-14.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 26EB2C433ED for ; Mon, 17 May 2021 18:09:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EF33261285 for ; Mon, 17 May 2021 18:09:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242239AbhEQSLA (ORCPT ); Mon, 17 May 2021 14:11:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:35204 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236729AbhEQSK5 (ORCPT ); Mon, 17 May 2021 14:10:57 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9144D611BF; Mon, 17 May 2021 18:09:40 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1lihgQ-001v3k-MQ; Mon, 17 May 2021 19:09:38 +0100 Date: Mon, 17 May 2021 19:09:37 +0100 Message-ID: <87r1i5teou.wl-maz@kernel.org> From: Marc Zyngier To: Steven Price Cc: Catalin Marinas , 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 v12 8/8] KVM: arm64: Document MTE capability and ioctl In-Reply-To: <20210517123239.8025-9-steven.price@arm.com> References: <20210517123239.8025-1-steven.price@arm.com> <20210517123239.8025-9-steven.price@arm.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: steven.price@arm.com, catalin.marinas@arm.com, will@kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Dave.Martin@arm.com, mark.rutland@arm.com, tglx@linutronix.de, qemu-devel@nongnu.org, quintela@redhat.com, dgilbert@redhat.com, richard.henderson@linaro.org, peter.maydell@linaro.org, Haibo.Xu@arm.com, drjones@redhat.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 17 May 2021 13:32:39 +0100, Steven Price wrote: > > A new capability (KVM_CAP_ARM_MTE) identifies that the kernel supports > granting a guest access to the tags, and provides a mechanism for the > VMM to enable it. > > A new ioctl (KVM_ARM_MTE_COPY_TAGS) provides a simple way for a VMM to > access the tags of a guest without having to maintain a PROT_MTE mapping > in userspace. The above capability gates access to the ioctl. > > Signed-off-by: Steven Price > --- > Documentation/virt/kvm/api.rst | 53 ++++++++++++++++++++++++++++++++++ > 1 file changed, 53 insertions(+) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index 22d077562149..a31661b870ba 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -5034,6 +5034,40 @@ see KVM_XEN_VCPU_SET_ATTR above. > The KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADJUST type may not be used > with the KVM_XEN_VCPU_GET_ATTR ioctl. > > +4.130 KVM_ARM_MTE_COPY_TAGS > +--------------------------- > + > +:Capability: KVM_CAP_ARM_MTE > +:Architectures: arm64 > +:Type: vm ioctl > +:Parameters: struct kvm_arm_copy_mte_tags > +:Returns: 0 on success, < 0 on error > + > +:: > + > + struct kvm_arm_copy_mte_tags { > + __u64 guest_ipa; > + __u64 length; > + union { > + void __user *addr; > + __u64 padding; > + }; > + __u64 flags; > + __u64 reserved[2]; > + }; This doesn't exactly match the structure in the previous patch :-(. > + > +Copies Memory Tagging Extension (MTE) tags to/from guest tag memory. The > +``guest_ipa`` and ``length`` fields must be ``PAGE_SIZE`` aligned. The ``addr`` > +fieldmust point to a buffer which the tags will be copied to or from. > + > +``flags`` specifies the direction of copy, either ``KVM_ARM_TAGS_TO_GUEST`` or > +``KVM_ARM_TAGS_FROM_GUEST``. > + > +The size of the buffer to store the tags is ``(length / MTE_GRANULE_SIZE)`` Should we add a UAPI definition for MTE_GRANULE_SIZE? > +bytes (i.e. 1/16th of the corresponding size). Each byte contains a single tag > +value. This matches the format of ``PTRACE_PEEKMTETAGS`` and > +``PTRACE_POKEMTETAGS``. > + > 5. The kvm_run structure > ======================== > > @@ -6362,6 +6396,25 @@ default. > > See Documentation/x86/sgx/2.Kernel-internals.rst for more details. > > +7.26 KVM_CAP_ARM_MTE > +-------------------- > + > +:Architectures: arm64 > +:Parameters: none > + > +This capability indicates that KVM (and the hardware) supports exposing the > +Memory Tagging Extensions (MTE) to the guest. It must also be enabled by the > +VMM before the guest will be granted access. > + > +When enabled the guest is able to access tags associated with any memory given > +to the guest. KVM will ensure that the pages are flagged ``PG_mte_tagged`` so > +that the tags are maintained during swap or hibernation of the host; however > +the VMM needs to manually save/restore the tags as appropriate if the VM is > +migrated. > + > +When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to > +perform a bulk copy of tags to/from the guest. > + Missing limitation to AArch64 guests. Thanks, M. -- Without deviation from the norm, progress is not possible.