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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id E2FB9C54E94 for ; Thu, 26 Jan 2023 11:48:50 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pL0jz-0003YM-IN; Thu, 26 Jan 2023 06:48:27 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pL0jm-0003Ob-2e for qemu-devel@nongnu.org; Thu, 26 Jan 2023 06:48:25 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pL0jX-0004Ao-J0 for qemu-devel@nongnu.org; Thu, 26 Jan 2023 06:48:02 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674733677; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=gW18Ss9Lzrp4NFwKCB2kFJc4bmfBf93FYizzDbkiEwY=; b=GVcwIWEkpESv505a7IwlrE/oMVuD4Zj8q4EnVR/xHnuW81/o3hBrQjn7fjpdjbLV+Ni+9q T8Nw1A0bLuV9J+8EMvq3gFxGcWBoZalbjzsKdxlICm+XGEGPjV5iCzlHPlxjPjvbBenzYH zlwLcB0bl/6KXgb87D86bm9JNrMlKS4= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-304-zsevXJBhMB2J7rGIjH5OYg-1; Thu, 26 Jan 2023 06:47:56 -0500 X-MC-Unique: zsevXJBhMB2J7rGIjH5OYg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id F03DD801779; Thu, 26 Jan 2023 11:47:55 +0000 (UTC) Received: from localhost (unknown [10.39.193.233]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 43C98401530E; Thu, 26 Jan 2023 11:47:52 +0000 (UTC) From: Cornelia Huck To: Eric Auger , Peter Maydell , Thomas Huth , Laurent Vivier Cc: qemu-arm@nongnu.org, qemu-devel@nongnu.org, kvm@vger.kernel.org, "Dr. David Alan Gilbert" , Juan Quintela , Gavin Shan Subject: Re: [PATCH v4 1/2] arm/kvm: add support for MTE In-Reply-To: <44d82d98-6a27-f4d3-9773-670231f82c63@redhat.com> Organization: Red Hat GmbH References: <20230111161317.52250-1-cohuck@redhat.com> <20230111161317.52250-2-cohuck@redhat.com> <44d82d98-6a27-f4d3-9773-670231f82c63@redhat.com> User-Agent: Notmuch/0.37 (https://notmuchmail.org) Date: Thu, 26 Jan 2023 12:47:49 +0100 Message-ID: <877cx9y0t6.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.133.124; envelope-from=cohuck@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, 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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Jan 23 2023, Eric Auger wrote: > Hi Connie, > On 1/11/23 17:13, Cornelia Huck wrote: >> Introduce a new cpu feature flag to control MTE support. To preserve >> backwards compatibility for tcg, MTE will continue to be enabled as >> long as tag memory has been provided. >> >> If MTE has been enabled, we need to disable migration, as we do not > this only applies to KVM acceleration "If MTE has been enabled with KVM," ... >> yet have a way to migrate the tags as well. Therefore, MTE will stay >> off with KVM unless requested explicitly. >> >> Signed-off-by: Cornelia Huck >> --- >> docs/system/arm/cpu-features.rst | 21 +++++ >> hw/arm/virt.c | 2 +- >> target/arm/cpu.c | 18 ++--- >> target/arm/cpu.h | 1 + >> target/arm/cpu64.c | 133 +++++++++++++++++++++++++++++++ >> target/arm/internals.h | 1 + >> target/arm/kvm64.c | 5 ++ >> target/arm/kvm_arm.h | 12 +++ >> target/arm/monitor.c | 1 + >> 9 files changed, 181 insertions(+), 13 deletions(-) >> >> diff --git a/docs/system/arm/cpu-features.rst b/docs/system/arm/cpu-features.rst >> index 00c444042ff5..e278650c837e 100644 >> --- a/docs/system/arm/cpu-features.rst >> +++ b/docs/system/arm/cpu-features.rst >> @@ -443,3 +443,24 @@ As with ``sve-default-vector-length``, if the default length is larger >> than the maximum vector length enabled, the actual vector length will >> be reduced. If this property is set to ``-1`` then the default vector >> length is set to the maximum possible length. >> + >> +MTE CPU Property >> +================ >> + >> +The ``mte`` property controls the Memory Tagging Extension. For TCG, it requires >> +presence of tag memory (which can be turned on for the ``virt`` machine via >> +``mte=on``). For KVM, it requires the ``KVM_CAP_ARM_MTE`` capability; until >> +proper migration support is implemented, enabling MTE will install a migration >> +blocker. > maybe re-emphasize: when KVM is enabled I think it's explicit enough, since it is in the "For KVM" phrase? >> + >> +If not specified explicitly via ``on`` or ``off``, MTE will be available >> +according to the following rules: >> + >> +* When TCG is used, MTE will be available iff tag memory is available; i.e. it > suggestion: is available at machine level It's only configured at machine level, not sure if that clarifies anything? >> + preserves the behaviour prior to introduction of the feature. > s/prior to/prior to the ? ok >> + >> +* When KVM is used, MTE will default to off, so that migration will not >> + unintentionally be blocked. >> + >> +* Other accelerators currently don't support MTE. >> + >> diff --git a/hw/arm/virt.c b/hw/arm/virt.c >> index ea2413a0bad7..42359e256ad0 100644 >> --- a/hw/arm/virt.c >> +++ b/hw/arm/virt.c >> @@ -2136,7 +2136,7 @@ static void machvirt_init(MachineState *machine) >> >> if (vms->mte && (kvm_enabled() || hvf_enabled())) { >> error_report("mach-virt: %s does not support providing " >> - "MTE to the guest CPU", >> + "emulated MTE to the guest CPU", > each time I read this message I feel difficult to understand it. Why not > replacing by > "mach-virt does not support tag memory with %s acceleration" or > something alike? Hmm... well, it does not support tag memory with kvm/hvf, and the consequence of this is that kvm/hvf cannot provide support for emulated mte... what about "mach-virt: tag memory not supported with %s, emulated MTE cannot be provided to the guest CPU" Might be a bit long, though. >> kvm_enabled() ? "KVM" : "HVF"); >> exit(1); >> } (...) >> +static void aarch64_cpu_set_mte(Object *obj, Visitor *v, const char *name, >> + void *opaque, Error **errp) >> +{ >> + ARMCPU *cpu = ARM_CPU(obj); >> + >> + visit_type_OnOffAuto(v, name, &cpu->prop_mte, errp); >> + > nit: spare void line will drop >> +} >> + >> +static void aarch64_add_mte_properties(Object *obj) >> +{ >> + /* >> + * For tcg, "AUTO" means turn on mte if tag memory has been provided, and >> + * turn it off (without error) if not. >> + * For kvm, "AUTO" currently means mte off, as migration is not supported >> + * yet. >> + * For all others, "AUTO" means mte off. >> + */ >> + object_property_add(obj, "mte", "OnOffAuto", aarch64_cpu_get_mte, >> + aarch64_cpu_set_mte, NULL, NULL); >> +} >> + >> +static inline bool arm_machine_has_tag_memory(void) >> +{ >> +#ifndef CONFIG_USER_ONLY >> + Object *obj = object_dynamic_cast(qdev_get_machine(), TYPE_VIRT_MACHINE); >> + >> + /* so far, only the virt machine has support for tag memory */ >> + if (obj) { >> + VirtMachineState *vms = VIRT_MACHINE(obj); >> + >> + return vms->mte; >> + } >> +#endif >> + return false; >> +} >> + >> +void arm_cpu_mte_finalize(ARMCPU *cpu, Error **errp) >> +{ >> + bool enable_mte; >> + >> + switch (cpu->prop_mte) { >> + case ON_OFF_AUTO_OFF: >> + enable_mte = false; >> + break; >> + case ON_OFF_AUTO_ON: >> + if (!kvm_enabled()) { >> + if (cpu_isar_feature(aa64_mte, cpu)) { >> + if (!arm_machine_has_tag_memory()) { >> + error_setg(errp, "mte=on requires tag memory"); >> + return; >> + } >> + } else { >> + error_setg(errp, "mte not provided"); > mte not supported by this CPU type? yes, probably better >> + return; >> + } >> + } >> +#ifdef CONFIG_KVM >> + if (kvm_enabled() && !kvm_arm_mte_supported()) { > as you have stubs for both, is the #ifdef needed? see prior discussion :) Doesn't look like it. >> + error_setg(errp, "mte not supported by kvm"); >> + return; >> + } >> +#endif >> + enable_mte = true; >> + break; >> + default: /* AUTO */ >> + if (!kvm_enabled()) { >> + if (cpu_isar_feature(aa64_mte, cpu)) { >> + /* >> + * Tie mte enablement to presence of tag memory, in order to >> + * preserve pre-existing behaviour. >> + */ >> + enable_mte = arm_machine_has_tag_memory(); >> + } else { >> + enable_mte = false; >> + } >> + break; >> + } else { >> + /* >> + * This cannot yet be >> + * enable_mte = kvm_arm_mte_supported(); >> + * as we don't support migration yet. >> + */ >> + enable_mte = false; >> + } >> + } >> + >> + if (!enable_mte) { >> + /* Disable MTE feature bits. */ >> + cpu->isar.id_aa64pfr1 = >> + FIELD_DP64(cpu->isar.id_aa64pfr1, ID_AA64PFR1, MTE, 0); >> + return; >> + } >> + >> + /* accelerator-specific enablement */ >> + if (kvm_enabled()) { >> +#ifdef CONFIG_KVM >> + if (kvm_vm_enable_cap(kvm_state, KVM_CAP_ARM_MTE, 0)) { >> + error_setg(errp, "Failed to enable KVM_CAP_ARM_MTE"); > nit: return and remove the else? I've reworked that anyway (no need to enable a vm cap for every cpu.) >> + } else { >> + /* TODO: add proper migration support with MTE enabled */ >> + if (!mte_migration_blocker) { >> + error_setg(&mte_migration_blocker, >> + "Live migration disabled due to MTE enabled"); >> + if (migrate_add_blocker(mte_migration_blocker, NULL)) { > Can't you pass the erro directly to migrate_add_blocker. Also in > arm_gicv3_its_kvm.c or virtio-gpu-pci, < 0 is checked. Maybe worth to > double check the rationale. I've rewritten that in the meanwhile as well :) >> + error_setg(errp, "Failed to add MTE migration blocker"); >> + error_free(mte_migration_blocker); >> + mte_migration_blocker = NULL; >> + } >> + } >> + } >> +#endif >> + } >> +}