From nobody Tue Feb 10 00:22:41 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=arm.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1623661758810715.2755630470806; Mon, 14 Jun 2021 02:09:18 -0700 (PDT) Received: from localhost ([::1]:37382 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lsiar-0000Hf-Qu for importer@patchew.org; Mon, 14 Jun 2021 05:09:17 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:50698) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lsiXl-0001S2-IT for qemu-devel@nongnu.org; Mon, 14 Jun 2021 05:06:05 -0400 Received: from foss.arm.com ([217.140.110.172]:51024) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lsiXj-00064j-5z for qemu-devel@nongnu.org; Mon, 14 Jun 2021 05:06:05 -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 4A4BB1FB; Mon, 14 Jun 2021 02:06:02 -0700 (PDT) Received: from e112269-lin.arm.com (autoplooker.cambridge.arm.com [10.1.194.57]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 817AE3F694; Mon, 14 Jun 2021 02:05:59 -0700 (PDT) From: Steven Price To: Catalin Marinas , Marc Zyngier , Will Deacon Subject: [PATCH v15 7/7] KVM: arm64: Document MTE capability and ioctl Date: Mon, 14 Jun 2021 10:05:25 +0100 Message-Id: <20210614090525.4338-8-steven.price@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210614090525.4338-1-steven.price@arm.com> References: <20210614090525.4338-1-steven.price@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=217.140.110.172; envelope-from=steven.price@arm.com; helo=foss.arm.com X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, 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, Dave Martin , Juan Quintela , Richard Henderson , linux-kernel@vger.kernel.org, Steven Price , James Morse , Julien Thierry , Thomas Gleixner , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Type: text/plain; charset="utf-8" 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. Reviewed-by: Catalin Marinas Signed-off-by: Steven Price --- Documentation/virt/kvm/api.rst | 57 ++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 22d077562149..d412928e50cd 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -5034,6 +5034,43 @@ 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. =20 +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: number of bytes copied, < 0 on error (-EINVAL for incorrect + arguments, -EFAULT if memory cannot be accessed). + +:: + + struct kvm_arm_copy_mte_tags { + __u64 guest_ipa; + __u64 length; + void __user *addr; + __u64 flags; + __u64 reserved[2]; + }; + +Copies Memory Tagging Extension (MTE) tags to/from guest tag memory. The +``guest_ipa`` and ``length`` fields must be ``PAGE_SIZE`` aligned. The ``a= ddr`` +field must 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 / 16)`` bytes +(granules in MTE are 16 bytes long). Each byte contains a single tag +value. This matches the format of ``PTRACE_PEEKMTETAGS`` and +``PTRACE_POKEMTETAGS``. + +If an error occurs before any data is copied then a negative error code is +returned. If some tags have been copied before an error occurs then the nu= mber +of bytes successfully copied is returned. If the call completes successful= ly +then ``length`` is returned. + 5. The kvm_run structure =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 @@ -6362,6 +6399,26 @@ default. =20 See Documentation/x86/sgx/2.Kernel-internals.rst for more details. =20 +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 t= he +VMM before creating any VCPUs to allow the guest access. Note that MTE is = only +available to a guest running in AArch64 mode and enabling this capability = will +cause attempts to create AArch32 VCPUs to fail. + +When enabled the guest is able to access tags associated with any memory g= iven +to the guest. KVM will ensure 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. + 8. Other capabilities. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 --=20 2.20.1