From: Zengruan Ye yezengruan@huawei.com
virt inclusion category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I8WMFU CVE: NA
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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 4.19.87, HiSilicon Kunpeng920, 8 CPUs guest: kernel 4.19.87, 16 vCPUs
test-case | after-patch | before-patch ----------------------------------------+-------------------+------------------ Dhrystone 2 using register variables | 338955728.5 lps | 339266319.5 lps Double-Precision Whetstone | 30634.9 MWIPS | 30884.4 MWIPS Execl Throughput | 6753.2 lps | 3580.1 lps File Copy 1024 bufsize 2000 maxblocks | 490048.0 KBps | 313282.3 KBps File Copy 256 bufsize 500 maxblocks | 129662.5 KBps | 83550.7 KBps File Copy 4096 bufsize 8000 maxblocks | 1552551.5 KBps | 814327.0 KBps Pipe Throughput | 8976422.5 lps | 9048628.4 lps Pipe-based Context Switching | 258641.7 lps | 252925.9 lps Process Creation | 5312.2 lps | 4507.9 lps Shell Scripts (1 concurrent) | 8704.2 lpm | 6720.9 lpm Shell Scripts (8 concurrent) | 1708.8 lpm | 607.2 lpm System Call Overhead | 3714444.7 lps | 3746386.8 lps ----------------------------------------+-------------------+------------------ System Benchmarks Index Score | 2270.6 | 1679.2
Signed-off-by: Zengruan Ye yezengruan@huawei.com Signed-off-by: lishusen lishusen2@huawei.com --- arch/arm64/include/asm/paravirt.h | 3 + arch/arm64/kernel/paravirt.c | 107 ++++++++++++++++++++++++++++++ arch/arm64/kvm/arm.c | 2 + include/linux/cpuhotplug.h | 1 + 4 files changed, 113 insertions(+)
diff --git a/arch/arm64/include/asm/paravirt.h b/arch/arm64/include/asm/paravirt.h index 53282dc429f8..4e35851bcecf 100644 --- a/arch/arm64/include/asm/paravirt.h +++ b/arch/arm64/include/asm/paravirt.h @@ -20,6 +20,8 @@ static inline u64 paravirt_steal_clock(int cpu)
int __init pv_time_init(void);
+int __init pv_sched_init(void); + __visible bool __native_vcpu_is_preempted(int cpu); DECLARE_STATIC_CALL(pv_vcpu_preempted, __native_vcpu_is_preempted);
@@ -31,6 +33,7 @@ static inline bool pv_vcpu_is_preempted(int cpu) #else
#define pv_time_init() do {} while (0) +#define pv_sched_init() do {} while (0)
#endif // CONFIG_PARAVIRT
diff --git a/arch/arm64/kernel/paravirt.c b/arch/arm64/kernel/paravirt.c index aa718d6a9274..e0c862f8f656 100644 --- a/arch/arm64/kernel/paravirt.c +++ b/arch/arm64/kernel/paravirt.c @@ -22,6 +22,7 @@
#include <asm/paravirt.h> #include <asm/pvclock-abi.h> +#include <asm/pvsched-abi.h> #include <asm/smp_plat.h>
struct static_key paravirt_steal_enabled; @@ -174,3 +175,109 @@ int __init pv_time_init(void)
return 0; } + + +DEFINE_PER_CPU(struct pvsched_vcpu_state, pvsched_vcpu_region) __aligned(64); +EXPORT_PER_CPU_SYMBOL(pvsched_vcpu_region); + +static bool kvm_vcpu_is_preempted(int cpu) +{ + struct pvsched_vcpu_state *reg; + u32 preempted; + + reg = &per_cpu(pvsched_vcpu_region, cpu); + if (!reg) { + pr_warn_once("PV sched enabled but not configured for cpu %d\n", + cpu); + return false; + } + + preempted = le32_to_cpu(READ_ONCE(reg->preempted)); + + return !!preempted; +} + +static int pvsched_vcpu_state_dying_cpu(unsigned int cpu) +{ + struct pvsched_vcpu_state *reg; + struct arm_smccc_res res; + + reg = this_cpu_ptr(&pvsched_vcpu_region); + if (!reg) + return -EFAULT; + + arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_SCHED_IPA_RELEASE, &res); + memset(reg, 0, sizeof(*reg)); + + return 0; +} + +static int init_pvsched_vcpu_state(unsigned int cpu) +{ + struct pvsched_vcpu_state *reg; + struct arm_smccc_res res; + + reg = this_cpu_ptr(&pvsched_vcpu_region); + if (!reg) + return -EFAULT; + + /* Pass the memory address to host via hypercall */ + arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_SCHED_IPA_INIT, + virt_to_phys(reg), &res); + + return 0; +} + +static int kvm_arm_init_pvsched(void) +{ + int ret; + + ret = cpuhp_setup_state(CPUHP_AP_ARM_KVM_PVSCHED_STARTING, + "hypervisor/arm/pvsched:starting", + init_pvsched_vcpu_state, + pvsched_vcpu_state_dying_cpu); + + if (ret < 0) { + pr_warn("PV sched init failed\n"); + return ret; + } + + return 0; +} + +static bool has_kvm_pvsched(void) +{ + struct arm_smccc_res res; + + /* To detect the presence of PV sched support we require SMCCC 1.1+ */ + if (arm_smccc_1_1_get_conduit() == SMCCC_CONDUIT_NONE) + return false; + + arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID, + ARM_SMCCC_HV_PV_SCHED_FEATURES, &res); + + return (res.a0 == SMCCC_RET_SUCCESS); +} + +int __init pv_sched_init(void) +{ + int ret; + + if (is_hyp_mode_available()) + return 0; + + if (!has_kvm_pvsched()) { + pr_warn("PV sched is not available\n"); + return 0; + } + + ret = kvm_arm_init_pvsched(); + if (ret) + return ret; + + static_call_update(pv_vcpu_preempted, kvm_vcpu_is_preempted); + pr_info("using PV sched preempted\n"); + + return 0; +} +early_initcall(pv_sched_init); diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 9750bfba6f4c..c3774a172ff3 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -1383,6 +1383,8 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
spin_unlock(&vcpu->arch.mp_state_lock);
+ kvm_arm_pvsched_vcpu_init(&vcpu->arch); + return 0; }
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index 624d4a38c358..f94a1b8e34e0 100644 --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -190,6 +190,7 @@ enum cpuhp_state { CPUHP_AP_DUMMY_TIMER_STARTING, CPUHP_AP_ARM_XEN_STARTING, CPUHP_AP_ARM_XEN_RUNSTATE_STARTING, + CPUHP_AP_ARM_KVM_PVSCHED_STARTING, CPUHP_AP_ARM_CORESIGHT_STARTING, CPUHP_AP_ARM_CORESIGHT_CTI_STARTING, CPUHP_AP_ARM64_ISNDEP_STARTING,