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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id k16sm2974569ejd.78.2021.01.15.01.20.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Jan 2021 01:20:24 -0800 (PST) From: Vitaly Kuznetsov To: Igor Mammedov Subject: Re: [PATCH v3 18/19] i386: provide simple 'hv-default=on' option In-Reply-To: <20210115031142.7c171a7f@redhat.com> References: <20210107150640.539239-1-vkuznets@redhat.com> <20210107151449.541062-1-vkuznets@redhat.com> <20210115031142.7c171a7f@redhat.com> Date: Fri, 15 Jan 2021 10:20:23 +0100 Message-ID: <87h7ni7e08.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=vkuznets@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=216.205.24.124; envelope-from=vkuznets@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.248, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , Marcelo Tosatti , qemu-devel@nongnu.org, Eduardo Habkost Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Igor Mammedov writes: > On Thu, 7 Jan 2021 16:14:49 +0100 > Vitaly Kuznetsov wrote: > >> Enabling Hyper-V emulation for a Windows VM is a tiring experience as it >> requires listing all currently supported enlightenments ("hv-*" CPU >> features) explicitly. We do have 'hv-passthrough' mode enabling >> everything but it can't be used in production as it prevents migration. >> >> Introduce a simple 'hv-default=on' CPU flag enabling all currently supported >> Hyper-V enlightenments. Later, when new enlightenments get implemented, >> compat_props mechanism will be used to disable them for legacy machine types, >> this will keep 'hv-default=on' configurations migratable. >> >> Signed-off-by: Vitaly Kuznetsov >> --- >> docs/hyperv.txt | 16 +++++++++++++--- >> target/i386/cpu.c | 38 ++++++++++++++++++++++++++++++++++++++ >> target/i386/cpu.h | 5 +++++ >> 3 files changed, 56 insertions(+), 3 deletions(-) >> >> diff --git a/docs/hyperv.txt b/docs/hyperv.txt >> index 5df00da54fc4..a54c066cab09 100644 >> --- a/docs/hyperv.txt >> +++ b/docs/hyperv.txt >> @@ -17,10 +17,20 @@ compatible hypervisor and use Hyper-V specific features. >> >> 2. Setup >> ========= >> -No Hyper-V enlightenments are enabled by default by either KVM or QEMU. In >> -QEMU, individual enlightenments can be enabled through CPU flags, e.g: >> +All currently supported Hyper-V enlightenments can be enabled by specifying >> +'hv-default=on' CPU flag: >> >> - qemu-system-x86_64 --enable-kvm --cpu host,hv_relaxed,hv_vpindex,hv_time, ... >> + qemu-system-x86_64 --enable-kvm --cpu host,hv-default ... >> + >> +Alternatively, it is possible to do fine-grained enablement through CPU flags, >> +e.g: >> + >> + qemu-system-x86_64 --enable-kvm --cpu host,hv-relaxed,hv-vpindex,hv-time ... > > I'd put here not '...' but rather recommended list of flags, and update > it every time when new feature added if necessary. > This is an example of fine-grained enablement, there is no point to put all the existing flags there (hv-default is the only recommended way now, the rest is 'expert'/'debugging'). > (not to mention that if we had it to begin with, then new 'hv-default' won't > be necessary, I still see it as functionality duplication but I will not oppose it) > Unfortunately, upper layer tools don't read this doc and update themselves to enable new features when they appear. Similarly, if when these tools use '-machine q35' they get all the new features we add automatically, right? > >> +It is also possible to disable individual enlightenments from the default list, >> +this can be used for debugging purposes: >> + >> + qemu-system-x86_64 --enable-kvm --cpu host,hv-default=on,hv-evmcs=off ... >> >> Sometimes there are dependencies between enlightenments, QEMU is supposed to >> check that the supplied configuration is sane. >> diff --git a/target/i386/cpu.c b/target/i386/cpu.c >> index 48007a876e32..99338de00f78 100644 >> --- a/target/i386/cpu.c >> +++ b/target/i386/cpu.c >> @@ -4552,6 +4552,24 @@ static void x86_cpuid_set_tsc_freq(Object *obj, Visitor *v, const char *name, >> cpu->env.tsc_khz = cpu->env.user_tsc_khz = value / 1000; >> } >> >> +static bool x86_hv_default_get(Object *obj, Error **errp) >> +{ >> + X86CPU *cpu = X86_CPU(obj); >> + >> + return cpu->hyperv_default; >> +} >> + >> +static void x86_hv_default_set(Object *obj, bool value, Error **errp) >> +{ >> + X86CPU *cpu = X86_CPU(obj); >> + >> + cpu->hyperv_default = value; >> + >> + if (value) { >> + cpu->hyperv_features |= cpu->hyperv_default_features; > > s/|="/=/ please, > i.e. no option overrides whatever was specified before to keep semantics consistent. > Hm, this doesn't matter for the most recent machine type as hyperv_default_features has all the features but imagine you're running an older machine type which doesn't have 'hv_feature'. Now your suggestion is if I do: 'hv_default,hv_feature=on' I will get "hyperv_default_features | hv_feature" but if I do 'hv_feature=on,hv_default' I will just get 'hyperv_default_features' (as hv_default enablement will overwrite everything) How is this consistent? >> + } >> +} >> + >> /* Generic getter for "feature-words" and "filtered-features" properties */ >> static void x86_cpu_get_feature_words(Object *obj, Visitor *v, >> const char *name, void *opaque, >> @@ -6955,10 +6973,26 @@ static void x86_cpu_initfn(Object *obj) >> object_property_add_alias(obj, "pause_filter", obj, "pause-filter"); >> object_property_add_alias(obj, "sse4_1", obj, "sse4.1"); >> object_property_add_alias(obj, "sse4_2", obj, "sse4.2"); >> + object_property_add_alias(obj, "hv_default", obj, "hv-default"); >> >> if (xcc->model) { >> x86_cpu_load_model(cpu, xcc->model); >> } >> + >> + /* Hyper-V features enabled with 'hv-default=on' */ >> + cpu->hyperv_default_features = BIT(HYPERV_FEAT_RELAXED) | >> + BIT(HYPERV_FEAT_VAPIC) | BIT(HYPERV_FEAT_TIME) | >> + BIT(HYPERV_FEAT_CRASH) | BIT(HYPERV_FEAT_RESET) | >> + BIT(HYPERV_FEAT_VPINDEX) | BIT(HYPERV_FEAT_RUNTIME) | >> + BIT(HYPERV_FEAT_SYNIC) | BIT(HYPERV_FEAT_STIMER) | >> + BIT(HYPERV_FEAT_FREQUENCIES) | BIT(HYPERV_FEAT_REENLIGHTENMENT) | >> + BIT(HYPERV_FEAT_TLBFLUSH) | BIT(HYPERV_FEAT_IPI) | >> + BIT(HYPERV_FEAT_STIMER_DIRECT); >> + >> + /* Enlightened VMCS is only available on Intel/VMX */ >> + if (kvm_hv_evmcs_available()) { >> + cpu->hyperv_default_features |= BIT(HYPERV_FEAT_EVMCS); >> + } > what if VVM is migrated to another host without evmcs, > will it change CPUID? > Evmcs is tightly coupled with VMX, we can't migrate when it's not there. >> } >> >> static int64_t x86_cpu_get_arch_id(CPUState *cs) >> @@ -7285,6 +7319,10 @@ static void x86_cpu_common_class_init(ObjectClass *oc, void *data) >> x86_cpu_get_crash_info_qom, NULL, NULL, NULL); >> #endif >> >> + object_class_property_add_bool(oc, "hv-default", >> + x86_hv_default_get, >> + x86_hv_default_set); >> + >> for (w = 0; w < FEATURE_WORDS; w++) { >> int bitnr; >> for (bitnr = 0; bitnr < 64; bitnr++) { >> diff --git a/target/i386/cpu.h b/target/i386/cpu.h >> index 6220cb2cabb9..8a484becb6b9 100644 >> --- a/target/i386/cpu.h >> +++ b/target/i386/cpu.h >> @@ -1657,6 +1657,11 @@ struct X86CPU { >> bool hyperv_synic_kvm_only; >> uint64_t hyperv_features; >> bool hyperv_passthrough; >> + >> + /* 'hv-default' enablement */ >> + uint64_t hyperv_default_features; >> + bool hyperv_default; >> + >> OnOffAuto hyperv_no_nonarch_cs; >> uint32_t hyperv_vendor_id[3]; >> uint32_t hyperv_interface_id[4]; > -- Vitaly