From 8ad357551797b1edc184fb9f6a4f80a6fa626459 Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Fri, 14 Mar 2014 11:00:21 +0100 Subject: KVM: s390: enable IBS for single running VCPUs This patch enables the IBS facility when a single VCPU is running. The facility is dynamically turned on/off as soon as other VCPUs enter/leave the stopped state. When this facility is operating, some instructions can be executed faster for single-cpu guests. Signed-off-by: David Hildenbrand Reviewed-by: Dominik Dingel Reviewed-by: Cornelia Huck Signed-off-by: Christian Borntraeger diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h index 0d45f6f..f0a1dc5 100644 --- a/arch/s390/include/asm/kvm_host.h +++ b/arch/s390/include/asm/kvm_host.h @@ -72,6 +72,7 @@ struct sca_block { #define CPUSTAT_ZARCH 0x00000800 #define CPUSTAT_MCDS 0x00000100 #define CPUSTAT_SM 0x00000080 +#define CPUSTAT_IBS 0x00000040 #define CPUSTAT_G 0x00000008 #define CPUSTAT_GED 0x00000004 #define CPUSTAT_J 0x00000002 @@ -411,6 +412,7 @@ struct kvm_arch{ int use_cmma; struct s390_io_adapter *adapters[MAX_S390_IO_ADAPTERS]; wait_queue_head_t ipte_wq; + spinlock_t start_stop_lock; }; #define KVM_HVA_ERR_BAD (-1UL) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 6c972d2..0a01744 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -458,6 +458,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) kvm->arch.css_support = 0; kvm->arch.use_irqchip = 0; + spin_lock_init(&kvm->arch.start_stop_lock); + return 0; out_nogmap: debug_unregister(kvm->arch.dbf); @@ -996,8 +998,15 @@ bool kvm_s390_cmma_enabled(struct kvm *kvm) return true; } +static bool ibs_enabled(struct kvm_vcpu *vcpu) +{ + return atomic_read(&vcpu->arch.sie_block->cpuflags) & CPUSTAT_IBS; +} + static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu) { +retry: + s390_vcpu_unblock(vcpu); /* * We use MMU_RELOAD just to re-arm the ipte notifier for the * guest prefix page. gmap_ipte_notify will wait on the ptl lock. @@ -1005,15 +1014,34 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu) * already finished. We might race against a second unmapper that * wants to set the blocking bit. Lets just retry the request loop. */ - while (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu)) { + if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu)) { int rc; rc = gmap_ipte_notify(vcpu->arch.gmap, vcpu->arch.sie_block->prefix, PAGE_SIZE * 2); if (rc) return rc; - s390_vcpu_unblock(vcpu); + goto retry; + } + + if (kvm_check_request(KVM_REQ_ENABLE_IBS, vcpu)) { + if (!ibs_enabled(vcpu)) { + trace_kvm_s390_enable_disable_ibs(vcpu->vcpu_id, 1); + atomic_set_mask(CPUSTAT_IBS, + &vcpu->arch.sie_block->cpuflags); + } + goto retry; } + + if (kvm_check_request(KVM_REQ_DISABLE_IBS, vcpu)) { + if (ibs_enabled(vcpu)) { + trace_kvm_s390_enable_disable_ibs(vcpu->vcpu_id, 0); + atomic_clear_mask(CPUSTAT_IBS, + &vcpu->arch.sie_block->cpuflags); + } + goto retry; + } + return 0; } @@ -1362,16 +1390,107 @@ int kvm_s390_vcpu_store_status(struct kvm_vcpu *vcpu, unsigned long addr) return kvm_s390_store_status_unloaded(vcpu, addr); } +static inline int is_vcpu_stopped(struct kvm_vcpu *vcpu) +{ + return atomic_read(&(vcpu)->arch.sie_block->cpuflags) & CPUSTAT_STOPPED; +} + +static void __disable_ibs_on_vcpu(struct kvm_vcpu *vcpu) +{ + kvm_check_request(KVM_REQ_ENABLE_IBS, vcpu); + kvm_make_request(KVM_REQ_DISABLE_IBS, vcpu); + exit_sie_sync(vcpu); +} + +static void __disable_ibs_on_all_vcpus(struct kvm *kvm) +{ + unsigned int i; + struct kvm_vcpu *vcpu; + + kvm_for_each_vcpu(i, vcpu, kvm) { + __disable_ibs_on_vcpu(vcpu); + } +} + +static void __enable_ibs_on_vcpu(struct kvm_vcpu *vcpu) +{ + kvm_check_request(KVM_REQ_DISABLE_IBS, vcpu); + kvm_make_request(KVM_REQ_ENABLE_IBS, vcpu); + exit_sie_sync(vcpu); +} + void kvm_s390_vcpu_start(struct kvm_vcpu *vcpu) { + int i, online_vcpus, started_vcpus = 0; + + if (!is_vcpu_stopped(vcpu)) + return; + trace_kvm_s390_vcpu_start_stop(vcpu->vcpu_id, 1); + /* Only one cpu at a time may enter/leave the STOPPED state. */ + spin_lock_bh(&vcpu->kvm->arch.start_stop_lock); + online_vcpus = atomic_read(&vcpu->kvm->online_vcpus); + + for (i = 0; i < online_vcpus; i++) { + if (!is_vcpu_stopped(vcpu->kvm->vcpus[i])) + started_vcpus++; + } + + if (started_vcpus == 0) { + /* we're the only active VCPU -> speed it up */ + __enable_ibs_on_vcpu(vcpu); + } else if (started_vcpus == 1) { + /* + * As we are starting a second VCPU, we have to disable + * the IBS facility on all VCPUs to remove potentially + * oustanding ENABLE requests. + */ + __disable_ibs_on_all_vcpus(vcpu->kvm); + } + atomic_clear_mask(CPUSTAT_STOPPED, &vcpu->arch.sie_block->cpuflags); + /* + * Another VCPU might have used IBS while we were offline. + * Let's play safe and flush the VCPU at startup. + */ + vcpu->arch.sie_block->ihcpu = 0xffff; + spin_unlock_bh(&vcpu->kvm->arch.start_stop_lock); + return; } void kvm_s390_vcpu_stop(struct kvm_vcpu *vcpu) { + int i, online_vcpus, started_vcpus = 0; + struct kvm_vcpu *started_vcpu = NULL; + + if (is_vcpu_stopped(vcpu)) + return; + trace_kvm_s390_vcpu_start_stop(vcpu->vcpu_id, 0); + /* Only one cpu at a time may enter/leave the STOPPED state. */ + spin_lock_bh(&vcpu->kvm->arch.start_stop_lock); + online_vcpus = atomic_read(&vcpu->kvm->online_vcpus); + atomic_set_mask(CPUSTAT_STOPPED, &vcpu->arch.sie_block->cpuflags); + __disable_ibs_on_vcpu(vcpu); + + for (i = 0; i < online_vcpus; i++) { + if (!is_vcpu_stopped(vcpu->kvm->vcpus[i])) { + started_vcpus++; + started_vcpu = vcpu->kvm->vcpus[i]; + } + } + + if (started_vcpus == 1) { + /* + * As we only have one VCPU left, we want to enable the + * IBS facility for that VCPU to speed it up. + */ + __enable_ibs_on_vcpu(started_vcpu); + } + + spin_unlock_bh(&vcpu->kvm->arch.start_stop_lock); + return; } static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu, diff --git a/arch/s390/kvm/trace-s390.h b/arch/s390/kvm/trace-s390.h index 34d4f8a..647e9d6 100644 --- a/arch/s390/kvm/trace-s390.h +++ b/arch/s390/kvm/trace-s390.h @@ -244,6 +244,28 @@ TRACE_EVENT(kvm_s390_enable_css, __entry->kvm) ); +/* + * Trace point for enabling and disabling interlocking-and-broadcasting + * suppression. + */ +TRACE_EVENT(kvm_s390_enable_disable_ibs, + TP_PROTO(unsigned int id, int state), + TP_ARGS(id, state), + + TP_STRUCT__entry( + __field(unsigned int, id) + __field(int, state) + ), + + TP_fast_assign( + __entry->id = id; + __entry->state = state; + ), + + TP_printk("%s ibs on cpu %d", + __entry->state ? "enabling" : "disabling", __entry->id) + ); + #endif /* _TRACE_KVMS390_H */ diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 820fc2e..1e125b0 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -134,6 +134,8 @@ static inline bool is_error_page(struct page *page) #define KVM_REQ_EPR_EXIT 20 #define KVM_REQ_SCAN_IOAPIC 21 #define KVM_REQ_GLOBAL_CLOCK_UPDATE 22 +#define KVM_REQ_ENABLE_IBS 23 +#define KVM_REQ_DISABLE_IBS 24 #define KVM_USERSPACE_IRQ_SOURCE_ID 0 #define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID 1 -- cgit v0.10.2