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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 15ADDC43462 for ; Wed, 19 May 2021 14:09:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E79F46135A for ; Wed, 19 May 2021 14:09:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347103AbhESOLA (ORCPT ); Wed, 19 May 2021 10:11:00 -0400 Received: from foss.arm.com ([217.140.110.172]:41372 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347040AbhESOK5 (ORCPT ); Wed, 19 May 2021 10:10:57 -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 D3F6431B; Wed, 19 May 2021 07:09:37 -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 5F3503F73B; Wed, 19 May 2021 07:09:35 -0700 (PDT) Subject: Re: [PATCH v12 8/8] KVM: arm64: Document MTE capability and ioctl To: Marc Zyngier 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 References: <20210517123239.8025-1-steven.price@arm.com> <20210517123239.8025-9-steven.price@arm.com> <87r1i5teou.wl-maz@kernel.org> From: Steven Price Message-ID: <3b4cca00-e81d-322e-6f65-4d0850aac5a5@arm.com> Date: Wed, 19 May 2021 15:09:23 +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: <87r1i5teou.wl-maz@kernel.org> 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 17/05/2021 19:09, Marc Zyngier wrote: > 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 :-(. :( I knew there was a reason I didn't include it in the documentation for the first 9 versions... I'll fix this up, thanks for spotting it. >> + >> +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? I wasn't sure whether to export this or not. The ioctl is based around the existing ptrace interface (PTRACE_{PEEK,POKE}MTETAGS) which doesn't expose a UAPI definition. Admittedly the documentation there also just says "16-byte granule" rather than MTE_GRANULE_SIZE. So I'll just remove the reference to MTE_GRANULE_SIZE in the documentation unless you feel that we should have a UAPI definition. >> +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. As mentioned previously it's not technically limited to AArch64, but I'll expand this to make it clear that MTE isn't usable from a AArch32 VCPU. Thanks, Steve 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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 C6850C433B4 for ; Wed, 19 May 2021 14:10:53 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 407F5611C2 for ; Wed, 19 May 2021 14:10:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 407F5611C2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:34142 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ljMuR-0008Mm-V4 for qemu-devel@archiver.kernel.org; Wed, 19 May 2021 10:10:51 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52556) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ljMtK-0007HA-Ml for qemu-devel@nongnu.org; Wed, 19 May 2021 10:09:42 -0400 Received: from foss.arm.com ([217.140.110.172]:34032) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ljMtH-0004lr-V2 for qemu-devel@nongnu.org; Wed, 19 May 2021 10:09:41 -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 D3F6431B; Wed, 19 May 2021 07:09:37 -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 5F3503F73B; Wed, 19 May 2021 07:09:35 -0700 (PDT) Subject: Re: [PATCH v12 8/8] KVM: arm64: Document MTE capability and ioctl To: Marc Zyngier References: <20210517123239.8025-1-steven.price@arm.com> <20210517123239.8025-9-steven.price@arm.com> <87r1i5teou.wl-maz@kernel.org> From: Steven Price Message-ID: <3b4cca00-e81d-322e-6f65-4d0850aac5a5@arm.com> Date: Wed, 19 May 2021 15:09:23 +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: <87r1i5teou.wl-maz@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=217.140.110.172; envelope-from=steven.price@arm.com; helo=foss.arm.com X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_MED=-2.3, 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, Catalin Marinas , Juan Quintela , Richard Henderson , linux-kernel@vger.kernel.org, Dave Martin , James Morse , linux-arm-kernel@lists.infradead.org, Thomas Gleixner , Will Deacon , kvmarm@lists.cs.columbia.edu, Julien Thierry Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 17/05/2021 19:09, Marc Zyngier wrote: > 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 :-(. :( I knew there was a reason I didn't include it in the documentation for the first 9 versions... I'll fix this up, thanks for spotting it. >> + >> +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? I wasn't sure whether to export this or not. The ioctl is based around the existing ptrace interface (PTRACE_{PEEK,POKE}MTETAGS) which doesn't expose a UAPI definition. Admittedly the documentation there also just says "16-byte granule" rather than MTE_GRANULE_SIZE. So I'll just remove the reference to MTE_GRANULE_SIZE in the documentation unless you feel that we should have a UAPI definition. >> +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. As mentioned previously it's not technically limited to AArch64, but I'll expand this to make it clear that MTE isn't usable from a AArch32 VCPU. Thanks, Steve 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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 74266C433B4 for ; Wed, 19 May 2021 14:09:43 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id E457D611C2 for ; Wed, 19 May 2021 14:09:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E457D611C2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 736934B53D; Wed, 19 May 2021 10:09:42 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id enomwU4B4g34; Wed, 19 May 2021 10:09:41 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 3FDDD4B522; Wed, 19 May 2021 10:09:41 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id C64C24B522 for ; Wed, 19 May 2021 10:09:39 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id NBn33KksOWfA for ; Wed, 19 May 2021 10:09:38 -0400 (EDT) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 5D7DA4B4FE for ; Wed, 19 May 2021 10:09:38 -0400 (EDT) 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 D3F6431B; Wed, 19 May 2021 07:09:37 -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 5F3503F73B; Wed, 19 May 2021 07:09:35 -0700 (PDT) Subject: Re: [PATCH v12 8/8] KVM: arm64: Document MTE capability and ioctl To: Marc Zyngier References: <20210517123239.8025-1-steven.price@arm.com> <20210517123239.8025-9-steven.price@arm.com> <87r1i5teou.wl-maz@kernel.org> From: Steven Price Message-ID: <3b4cca00-e81d-322e-6f65-4d0850aac5a5@arm.com> Date: Wed, 19 May 2021 15:09:23 +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: <87r1i5teou.wl-maz@kernel.org> Content-Language: en-GB Cc: "Dr. David Alan Gilbert" , qemu-devel@nongnu.org, Catalin Marinas , Juan Quintela , Richard Henderson , linux-kernel@vger.kernel.org, Dave Martin , linux-arm-kernel@lists.infradead.org, Thomas Gleixner , Will Deacon , kvmarm@lists.cs.columbia.edu X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On 17/05/2021 19:09, Marc Zyngier wrote: > 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 :-(. :( I knew there was a reason I didn't include it in the documentation for the first 9 versions... I'll fix this up, thanks for spotting it. >> + >> +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? I wasn't sure whether to export this or not. The ioctl is based around the existing ptrace interface (PTRACE_{PEEK,POKE}MTETAGS) which doesn't expose a UAPI definition. Admittedly the documentation there also just says "16-byte granule" rather than MTE_GRANULE_SIZE. So I'll just remove the reference to MTE_GRANULE_SIZE in the documentation unless you feel that we should have a UAPI definition. >> +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. As mentioned previously it's not technically limited to AArch64, but I'll expand this to make it clear that MTE isn't usable from a AArch32 VCPU. Thanks, Steve _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm 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=-15.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 2B2E9C433B4 for ; Wed, 19 May 2021 14:11:32 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id AD0FB611C2 for ; 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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 1ljMtK-00FWem-EV for linux-arm-kernel@lists.infradead.org; Wed, 19 May 2021 14:09:44 +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 D3F6431B; Wed, 19 May 2021 07:09:37 -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 5F3503F73B; Wed, 19 May 2021 07:09:35 -0700 (PDT) Subject: Re: [PATCH v12 8/8] KVM: arm64: Document MTE capability and ioctl To: Marc Zyngier 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 References: <20210517123239.8025-1-steven.price@arm.com> <20210517123239.8025-9-steven.price@arm.com> <87r1i5teou.wl-maz@kernel.org> From: Steven Price Message-ID: <3b4cca00-e81d-322e-6f65-4d0850aac5a5@arm.com> Date: Wed, 19 May 2021 15:09:23 +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: <87r1i5teou.wl-maz@kernel.org> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210519_070942_614703_51230D7F X-CRM114-Status: GOOD ( 28.07 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 17/05/2021 19:09, Marc Zyngier wrote: > 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 :-(. :( I knew there was a reason I didn't include it in the documentation for the first 9 versions... I'll fix this up, thanks for spotting it. >> + >> +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? I wasn't sure whether to export this or not. The ioctl is based around the existing ptrace interface (PTRACE_{PEEK,POKE}MTETAGS) which doesn't expose a UAPI definition. Admittedly the documentation there also just says "16-byte granule" rather than MTE_GRANULE_SIZE. So I'll just remove the reference to MTE_GRANULE_SIZE in the documentation unless you feel that we should have a UAPI definition. >> +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. As mentioned previously it's not technically limited to AArch64, but I'll expand this to make it clear that MTE isn't usable from a AArch32 VCPU. Thanks, Steve _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel