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[81.40.121.121]) by smtp.gmail.com with ESMTPSA id h13sm9623430wrx.17.2020.08.07.01.28.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 07 Aug 2020 01:28:35 -0700 (PDT) Subject: Re: [PATCH 3/7] target/arm/cpu: spe: Add an option to turn on/off vSPE support To: Haibo Xu , peter.maydell@linaro.org References: From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <5fd62d43-0cdb-d69f-c11c-4a0122b28396@amsat.org> Date: Fri, 7 Aug 2020 10:28:35 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2a00:1450:4864:20::342; envelope-from=philippe.mathieu.daude@gmail.com; helo=mail-wm1-x342.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. X-Spam_score_int: 0 X-Spam_score: 0.0 X-Spam_bar: / X-Spam_report: (0.0 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FORGED_FROMDOMAIN=1, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no 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: drjones@redhat.com, qemu-arm@nongnu.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Haibo, On 8/7/20 10:10 AM, Haibo Xu wrote: > Adds a spe=[on/off] option to enable/disable vSPE support in > guest vCPU. Note this option is only available for "-cpu host" > with KVM mode, and default value is on. > > Signed-off-by: Haibo Xu > --- > target/arm/cpu.c | 28 ++++++++++++++++++++++++++++ > target/arm/cpu.h | 3 +++ > 2 files changed, 31 insertions(+) > > diff --git a/target/arm/cpu.c b/target/arm/cpu.c > index 111579554f..40768b4d19 100644 > --- a/target/arm/cpu.c > +++ b/target/arm/cpu.c > @@ -1122,6 +1122,29 @@ static void arm_set_pmu(Object *obj, bool value, Error **errp) > cpu->has_pmu = value; > } > > +static bool arm_get_spe(Object *obj, Error **errp) > +{ > + ARMCPU *cpu = ARM_CPU(obj); > + > + return cpu->has_spe; > +} > + > +static void arm_set_spe(Object *obj, bool value, Error **errp) > +{ > + ARMCPU *cpu = ARM_CPU(obj); > + > + if (value) { > + if (kvm_enabled() && !kvm_arm_spe_supported()) { > + error_setg(errp, "'spe' feature not supported by KVM on this host"); > + return; > + } > + set_feature(&cpu->env, ARM_FEATURE_SPE); > + } else { > + unset_feature(&cpu->env, ARM_FEATURE_SPE); > + } > + cpu->has_spe = value; > +} > + > unsigned int gt_cntfrq_period_ns(ARMCPU *cpu) > { > /* > @@ -1195,6 +1218,11 @@ void arm_cpu_post_init(Object *obj) > object_property_add_bool(obj, "pmu", arm_get_pmu, arm_set_pmu); > } > > + if (arm_feature(&cpu->env, ARM_FEATURE_SPE)) { > + cpu->has_spe = true; Being a profiling feature, are you sure you want it to be ON by default? I'd expect the opposite, either being turned on via command line at startup or by a management layer at runtime, when someone is ready to record the perf events and analyze them. > + object_property_add_bool(obj, "spe", arm_get_spe, arm_set_spe); > + } > + > /* > * Allow user to turn off VFP and Neon support, but only for TCG -- > * KVM does not currently allow us to lie to the guest about its > diff --git a/target/arm/cpu.h b/target/arm/cpu.h > index 9e8ed423ea..fe0ac14386 100644 > --- a/target/arm/cpu.h > +++ b/target/arm/cpu.h > @@ -822,6 +822,8 @@ struct ARMCPU { > bool has_el3; > /* CPU has PMU (Performance Monitor Unit) */ > bool has_pmu; > + /* CPU has SPE (Statistical Profiling Extension) */ > + bool has_spe; > /* CPU has VFP */ > bool has_vfp; > /* CPU has Neon */ > @@ -1959,6 +1961,7 @@ enum arm_features { > ARM_FEATURE_VBAR, /* has cp15 VBAR */ > ARM_FEATURE_M_SECURITY, /* M profile Security Extension */ > ARM_FEATURE_M_MAIN, /* M profile Main Extension */ > + ARM_FEATURE_SPE, /* has SPE support */ > }; > > static inline int arm_feature(CPUARMState *env, int feature) >