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Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lXQdC-009WCo-1q for linux-arm-kernel@lists.infradead.org; Fri, 16 Apr 2021 15:43:43 +0000 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 895981396; Fri, 16 Apr 2021 08:43:40 -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 BBBE13F99C; Fri, 16 Apr 2021 08:43:37 -0700 (PDT) From: Steven Price To: Catalin Marinas , Marc Zyngier , Will Deacon Cc: Steven Price , 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: [PATCH v11 6/6] KVM: arm64: Document MTE capability and ioctl Date: Fri, 16 Apr 2021 16:43:09 +0100 Message-Id: <20210416154309.22129-7-steven.price@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210416154309.22129-1-steven.price@arm.com> References: <20210416154309.22129-1-steven.price@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210416_084342_211500_045D689A X-CRM114-Status: GOOD ( 12.75 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 1a2b5210cdbf..ccc84f21ba5e 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -4938,6 +4938,40 @@ 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. +4.131 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]; + }; + +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)`` +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 ======================== @@ -6227,6 +6261,25 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them. This capability can be used to check / enable 2nd DAWR feature provided by POWER10 processor. +7.23 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. + 8. Other capabilities. ======================