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([2a01:e0a:59e:9d80:527b:9dff:feef:3874]) by smtp.gmail.com with ESMTPSA id ez11-20020a05622a4c8b00b003afbf704c7csm8558178qtb.24.2023.01.23.05.50.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Jan 2023 05:50:16 -0800 (PST) Message-ID: <44d82d98-6a27-f4d3-9773-670231f82c63@redhat.com> Date: Mon, 23 Jan 2023 14:50:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.1 Subject: Re: [PATCH v4 1/2] arm/kvm: add support for MTE Content-Language: en-US To: Cornelia Huck , 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 References: <20230111161317.52250-1-cohuck@redhat.com> <20230111161317.52250-2-cohuck@redhat.com> From: Eric Auger In-Reply-To: <20230111161317.52250-2-cohuck@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=eauger@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 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, NICE_REPLY_A=-1.147, 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 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 > 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 > + > +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 > + preserves the behaviour prior to introduction of the feature. s/prior to/prior to the ? > + > +* 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? > kvm_enabled() ? "KVM" : "HVF"); > exit(1); > } > diff --git a/target/arm/cpu.c b/target/arm/cpu.c > index 5f63316dbf22..decab743d0d5 100644 > --- a/target/arm/cpu.c > +++ b/target/arm/cpu.c > @@ -1529,6 +1529,11 @@ void arm_cpu_finalize_features(ARMCPU *cpu, Error **errp) > error_propagate(errp, local_err); > return; > } > + arm_cpu_mte_finalize(cpu, &local_err); > + if (local_err != NULL) { > + error_propagate(errp, local_err); > + return; > + } > } > #endif > > @@ -1605,7 +1610,7 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp) > } > if (cpu->tag_memory) { > error_setg(errp, > - "Cannot enable %s when guest CPUs has MTE enabled", > + "Cannot enable %s when guest CPUs has tag memory enabled", > current_accel_name()); > return; > } > @@ -1984,17 +1989,6 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp) > ID_PFR1, VIRTUALIZATION, 0); > } > > -#ifndef CONFIG_USER_ONLY > - if (cpu->tag_memory == NULL && cpu_isar_feature(aa64_mte, cpu)) { > - /* > - * Disable the MTE feature bits if we do not have tag-memory > - * provided by the machine. > - */ > - cpu->isar.id_aa64pfr1 = > - FIELD_DP64(cpu->isar.id_aa64pfr1, ID_AA64PFR1, MTE, 0); > - } > -#endif > - > if (tcg_enabled()) { > /* > * Don't report the Statistical Profiling Extension in the ID > diff --git a/target/arm/cpu.h b/target/arm/cpu.h > index bf2bce046d56..f1a9015a7ed7 100644 > --- a/target/arm/cpu.h > +++ b/target/arm/cpu.h > @@ -1038,6 +1038,7 @@ struct ArchCPU { > bool prop_pauth; > bool prop_pauth_impdef; > bool prop_lpa2; > + OnOffAuto prop_mte; > > /* DCZ blocksize, in log_2(words), ie low 4 bits of DCZID_EL0 */ > uint32_t dcz_blocksize; > diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c > index 0e021960fb5b..3cf42ee05ca3 100644 > --- a/target/arm/cpu64.c > +++ b/target/arm/cpu64.c > @@ -29,6 +29,13 @@ > #include "qapi/visitor.h" > #include "hw/qdev-properties.h" > #include "internals.h" > +#include "migration/blocker.h" > +#include "qapi/qapi-visit-common.h" > +#include "hw/arm/virt.h" > + > +#ifdef CONFIG_KVM > +static Error *mte_migration_blocker; > +#endif > > static void aarch64_a35_initfn(Object *obj) > { > @@ -1096,6 +1103,130 @@ static void aarch64_neoverse_n1_initfn(Object *obj) > cpu->isar.reset_pmcr_el0 = 0x410c3000; > } > > +static void aarch64_cpu_get_mte(Object *obj, Visitor *v, const char *name, > + void *opaque, Error **errp) > +{ > + ARMCPU *cpu = ARM_CPU(obj); > + OnOffAuto mte = cpu->prop_mte; > + > + visit_type_OnOffAuto(v, name, &mte, errp); > +} > + > +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 > +} > + > +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? > + return; > + } > + } > +#ifdef CONFIG_KVM > + if (kvm_enabled() && !kvm_arm_mte_supported()) { as you have stubs for both, is the #ifdef needed? > + 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? > + } 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. > + error_setg(errp, "Failed to add MTE migration blocker"); > + error_free(mte_migration_blocker); > + mte_migration_blocker = NULL; > + } > + } > + } > +#endif > + } > +} > + > static void aarch64_host_initfn(Object *obj) > { > #if defined(CONFIG_KVM) > @@ -1104,6 +1235,7 @@ static void aarch64_host_initfn(Object *obj) > if (arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) { > aarch64_add_sve_properties(obj); > aarch64_add_pauth_properties(obj); > + aarch64_add_mte_properties(obj); > } > #elif defined(CONFIG_HVF) > ARMCPU *cpu = ARM_CPU(obj); > @@ -1300,6 +1432,7 @@ static void aarch64_max_initfn(Object *obj) > object_property_add(obj, "sve-max-vq", "uint32", cpu_max_get_sve_max_vq, > cpu_max_set_sve_max_vq, NULL, NULL); > qdev_property_add_static(DEVICE(obj), &arm_cpu_lpa2_property); > + aarch64_add_mte_properties(obj); > } > > static const ARMCPUInfo aarch64_cpus[] = { > diff --git a/target/arm/internals.h b/target/arm/internals.h > index d9555309df0f..4dc6d19be42b 100644 > --- a/target/arm/internals.h > +++ b/target/arm/internals.h > @@ -1348,6 +1348,7 @@ void arm_cpu_sve_finalize(ARMCPU *cpu, Error **errp); > void arm_cpu_sme_finalize(ARMCPU *cpu, Error **errp); > void arm_cpu_pauth_finalize(ARMCPU *cpu, Error **errp); > void arm_cpu_lpa2_finalize(ARMCPU *cpu, Error **errp); > +void arm_cpu_mte_finalize(ARMCPU *cpu, Error **errp); > #endif > > #ifdef CONFIG_USER_ONLY > diff --git a/target/arm/kvm64.c b/target/arm/kvm64.c > index 1197253d12f7..b777bd0a11d2 100644 > --- a/target/arm/kvm64.c > +++ b/target/arm/kvm64.c > @@ -764,6 +764,11 @@ bool kvm_arm_steal_time_supported(void) > return kvm_check_extension(kvm_state, KVM_CAP_STEAL_TIME); > } > > +bool kvm_arm_mte_supported(void) > +{ > + return kvm_check_extension(kvm_state, KVM_CAP_ARM_MTE); > +} > + > QEMU_BUILD_BUG_ON(KVM_ARM64_SVE_VQ_MIN != 1); > > uint32_t kvm_arm_sve_get_vls(CPUState *cs) > diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h > index 99017b635ce4..762443f8a7c0 100644 > --- a/target/arm/kvm_arm.h > +++ b/target/arm/kvm_arm.h > @@ -305,6 +305,13 @@ bool kvm_arm_pmu_supported(void); > */ > bool kvm_arm_sve_supported(void); > > +/** > + * kvm_arm_mte_supported: > + * > + * Returns: true if KVM can enable MTE, and false otherwise. > + */ > +bool kvm_arm_mte_supported(void); > + > /** > * kvm_arm_get_max_vm_ipa_size: > * @ms: Machine state handle > @@ -395,6 +402,11 @@ static inline bool kvm_arm_steal_time_supported(void) > return false; > } > > +static inline bool kvm_arm_mte_supported(void) > +{ > + return false; > +} > + > /* > * These functions should never actually be called without KVM support. > */ > diff --git a/target/arm/monitor.c b/target/arm/monitor.c > index ecdd5ee81742..c419c81612ed 100644 > --- a/target/arm/monitor.c > +++ b/target/arm/monitor.c > @@ -96,6 +96,7 @@ static const char *cpu_model_advertised_features[] = { > "sve1408", "sve1536", "sve1664", "sve1792", "sve1920", "sve2048", > "kvm-no-adjvtime", "kvm-steal-time", > "pauth", "pauth-impdef", > + "mte", > NULL > }; > Thanks Eric