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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, 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 9C28FC33CA3 for ; Thu, 9 Jan 2020 15:09:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 73B832080D for ; Thu, 9 Jan 2020 15:09:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732237AbgAIPJh (ORCPT ); Thu, 9 Jan 2020 10:09:37 -0500 Received: from foss.arm.com ([217.140.110.172]:60812 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732220AbgAIPJd (ORCPT ); Thu, 9 Jan 2020 10:09:33 -0500 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 2E08C1FB; Thu, 9 Jan 2020 07:09:32 -0800 (PST) Received: from [10.1.27.38] (e122027.cambridge.arm.com [10.1.27.38]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 336333F534; Thu, 9 Jan 2020 07:09:30 -0800 (PST) Subject: Re: [PATCH v2 6/6] KVM: arm64: Support the VCPU preemption check To: Zengruan Ye , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-doc@vger.kernel.org, virtualization@lists.linux-foundation.org Cc: maz@kernel.org, james.morse@arm.com, linux@armlinux.org.uk, suzuki.poulose@arm.com, julien.thierry.kdev@gmail.com, catalin.marinas@arm.com, mark.rutland@arm.com, will@kernel.org, daniel.lezcano@linaro.org References: <20191226135833.1052-1-yezengruan@huawei.com> <20191226135833.1052-7-yezengruan@huawei.com> From: Steven Price Message-ID: <5a1f6745-2deb-253b-7022-f2725d8d40ba@arm.com> Date: Thu, 9 Jan 2020 15:09:28 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <20191226135833.1052-7-yezengruan@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 26/12/2019 13:58, Zengruan Ye wrote: > Support the vcpu_is_preempted() functionality under KVM/arm64. This will > enhance lock performance on overcommitted hosts (more runnable VCPUs > than physical CPUs in the system) as doing busy waits for preempted > VCPUs will hurt system performance far worse than early yielding. > > unix benchmark result: > host: kernel 5.5.0-rc1, HiSilicon Kunpeng920, 8 CPUs > guest: kernel 5.5.0-rc1, 16 VCPUs > > test-case | after-patch | before-patch > ----------------------------------------+-------------------+------------------ > Dhrystone 2 using register variables | 334600751.0 lps | 335319028.3 lps > Double-Precision Whetstone | 32856.1 MWIPS | 32849.6 MWIPS > Execl Throughput | 3662.1 lps | 2718.0 lps > File Copy 1024 bufsize 2000 maxblocks | 432906.4 KBps | 158011.8 KBps > File Copy 256 bufsize 500 maxblocks | 116023.0 KBps | 37664.0 KBps > File Copy 4096 bufsize 8000 maxblocks | 1432769.8 KBps | 441108.8 KBps > Pipe Throughput | 6405029.6 lps | 6021457.6 lps > Pipe-based Context Switching | 185872.7 lps | 184255.3 lps > Process Creation | 4025.7 lps | 3706.6 lps > Shell Scripts (1 concurrent) | 6745.6 lpm | 6436.1 lpm > Shell Scripts (8 concurrent) | 998.7 lpm | 931.1 lpm > System Call Overhead | 3913363.1 lps | 3883287.8 lps > ----------------------------------------+-------------------+------------------ > System Benchmarks Index Score | 1835.1 | 1327.6 > > Signed-off-by: Zengruan Ye > --- > arch/arm64/include/asm/paravirt.h | 3 + > arch/arm64/kernel/paravirt.c | 117 ++++++++++++++++++++++++++++++ > arch/arm64/kernel/setup.c | 2 + > include/linux/cpuhotplug.h | 1 + > 4 files changed, 123 insertions(+) > > diff --git a/arch/arm64/include/asm/paravirt.h b/arch/arm64/include/asm/paravirt.h > index 7b1c81b544bb..ca3a2c7881f3 100644 > --- a/arch/arm64/include/asm/paravirt.h > +++ b/arch/arm64/include/asm/paravirt.h > @@ -29,6 +29,8 @@ static inline u64 paravirt_steal_clock(int cpu) > > int __init pv_time_init(void); > > +int __init pv_lock_init(void); > + > __visible bool __native_vcpu_is_preempted(int cpu); > > static inline bool pv_vcpu_is_preempted(int cpu) > @@ -39,6 +41,7 @@ static inline bool pv_vcpu_is_preempted(int cpu) > #else > > #define pv_time_init() do {} while (0) > +#define pv_lock_init() do {} while (0) > > #endif // CONFIG_PARAVIRT > > diff --git a/arch/arm64/kernel/paravirt.c b/arch/arm64/kernel/paravirt.c > index d8f1ba8c22ce..bd2ad6a17a26 100644 > --- a/arch/arm64/kernel/paravirt.c > +++ b/arch/arm64/kernel/paravirt.c > @@ -22,6 +22,7 @@ > #include > #include > #include > +#include > > struct static_key paravirt_steal_enabled; > struct static_key paravirt_steal_rq_enabled; > @@ -35,6 +36,10 @@ struct pv_time_stolen_time_region { > struct pvclock_vcpu_stolen_time *kaddr; > }; > > +struct pv_lock_state_region { > + struct pvlock_vcpu_state *kaddr; > +}; > + > static DEFINE_PER_CPU(struct pv_time_stolen_time_region, stolen_time_region); > > static bool steal_acc = true; > @@ -158,3 +163,115 @@ int __init pv_time_init(void) > > return 0; > } > + > +static DEFINE_PER_CPU(struct pv_lock_state_region, lock_state_region); > + > +static bool kvm_vcpu_is_preempted(int cpu) > +{ > + struct pv_lock_state_region *reg; > + __le64 preempted_le; > + > + reg = per_cpu_ptr(&lock_state_region, cpu); > + if (!reg->kaddr) { > + pr_warn_once("PV lock enabled but not configured for cpu %d\n", > + cpu); > + return false; > + } > + > + preempted_le = le64_to_cpu(READ_ONCE(reg->kaddr->preempted)); > + > + return !!(preempted_le & 1); According to the documentation preempted != 0 means preempted, but here you are checking the LSB. You need to be consistent about the ABI. > +} > + > +static int pvlock_vcpu_state_dying_cpu(unsigned int cpu) > +{ > + struct pv_lock_state_region *reg; > + > + reg = this_cpu_ptr(&lock_state_region); > + if (!reg->kaddr) > + return 0; > + > + memunmap(reg->kaddr); > + memset(reg, 0, sizeof(*reg)); > + > + return 0; > +} > + > +static int init_pvlock_vcpu_state(unsigned int cpu) > +{ > + struct pv_lock_state_region *reg; > + struct arm_smccc_res res; > + > + reg = this_cpu_ptr(&lock_state_region); > + > + arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_LOCK_PREEMPTED, &res); > + > + if (res.a0 == SMCCC_RET_NOT_SUPPORTED) { > + pr_warn("Failed to init PV lock data structure\n"); > + return -EINVAL; > + } > + > + reg->kaddr = memremap(res.a0, > + sizeof(struct pvlock_vcpu_state), > + MEMREMAP_WB); > + > + if (!reg->kaddr) { > + pr_warn("Failed to map PV lock data structure\n"); > + return -ENOMEM; > + } > + > + return 0; > +} > + > +static int kvm_arm_init_pvlock(void) > +{ > + int ret; > + > + ret = cpuhp_setup_state(CPUHP_AP_ARM_KVM_PVLOCK_STARTING, > + "hypervisor/arm/pvlock:starting", > + init_pvlock_vcpu_state, > + pvlock_vcpu_state_dying_cpu); > + if (ret < 0) { > + pr_warn("PV-lock init failed\n"); > + return ret; > + } > + > + return 0; > +} > + > +static bool has_kvm_pvlock(void) > +{ > + struct arm_smccc_res res; > + > + /* To detect the presence of PV lock support we require SMCCC 1.1+ */ > + if (psci_ops.smccc_version < SMCCC_VERSION_1_1) > + return false; > + > + arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID, > + ARM_SMCCC_HV_PV_LOCK_FEATURES, &res); As mentioned previously we could do with something more robust to check that the hypervisor is actually KVM before assuming that vendor specific IDs are valid. Steve > + > + if (res.a0 != SMCCC_RET_SUCCESS) > + return false; > + > + return true; > +} > + > +int __init pv_lock_init(void) > +{ > + int ret; > + > + if (is_hyp_mode_available()) > + return 0; > + > + if (!has_kvm_pvlock()) > + return 0; > + > + ret = kvm_arm_init_pvlock(); > + if (ret) > + return ret; > + > + pv_ops.lock.vcpu_is_preempted = kvm_vcpu_is_preempted; > + pr_info("using PV-lock preempted\n"); > + > + return 0; > +} > diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c > index 56f664561754..aa3a8b9e710f 100644 > --- a/arch/arm64/kernel/setup.c > +++ b/arch/arm64/kernel/setup.c > @@ -341,6 +341,8 @@ void __init setup_arch(char **cmdline_p) > smp_init_cpus(); > smp_build_mpidr_hash(); > > + pv_lock_init(); > + > /* Init percpu seeds for random tags after cpus are set up. */ > kasan_init_tags(); > > diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h > index e51ee772b9f5..f72ff95ab63a 100644 > --- a/include/linux/cpuhotplug.h > +++ b/include/linux/cpuhotplug.h > @@ -138,6 +138,7 @@ enum cpuhp_state { > CPUHP_AP_DUMMY_TIMER_STARTING, > CPUHP_AP_ARM_XEN_STARTING, > CPUHP_AP_ARM_KVMPV_STARTING, > + CPUHP_AP_ARM_KVM_PVLOCK_STARTING, > CPUHP_AP_ARM_CORESIGHT_STARTING, > CPUHP_AP_ARM64_ISNDEP_STARTING, > CPUHP_AP_SMPCFD_DYING, >