diff options
Diffstat (limited to 'arch/s390/kvm/kvm-s390.c')
| -rw-r--r-- | arch/s390/kvm/kvm-s390.c | 30 |
1 files changed, 22 insertions, 8 deletions
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 76b99149dc65..38223c4603c7 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -1435,15 +1435,19 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu) static void __start_cpu_timer_accounting(struct kvm_vcpu *vcpu) { WARN_ON_ONCE(vcpu->arch.cputm_start != 0); + raw_write_seqcount_begin(&vcpu->arch.cputm_seqcount); vcpu->arch.cputm_start = get_tod_clock_fast(); + raw_write_seqcount_end(&vcpu->arch.cputm_seqcount); } /* needs disabled preemption to protect from TOD sync and vcpu_load/put */ static void __stop_cpu_timer_accounting(struct kvm_vcpu *vcpu) { WARN_ON_ONCE(vcpu->arch.cputm_start == 0); + raw_write_seqcount_begin(&vcpu->arch.cputm_seqcount); vcpu->arch.sie_block->cputm -= get_tod_clock_fast() - vcpu->arch.cputm_start; vcpu->arch.cputm_start = 0; + raw_write_seqcount_end(&vcpu->arch.cputm_seqcount); } /* needs disabled preemption to protect from TOD sync and vcpu_load/put */ @@ -1480,28 +1484,37 @@ static void disable_cpu_timer_accounting(struct kvm_vcpu *vcpu) void kvm_s390_set_cpu_timer(struct kvm_vcpu *vcpu, __u64 cputm) { preempt_disable(); /* protect from TOD sync and vcpu_load/put */ + raw_write_seqcount_begin(&vcpu->arch.cputm_seqcount); if (vcpu->arch.cputm_enabled) vcpu->arch.cputm_start = get_tod_clock_fast(); vcpu->arch.sie_block->cputm = cputm; + raw_write_seqcount_end(&vcpu->arch.cputm_seqcount); preempt_enable(); } /* update and get the cpu timer - can also be called from other VCPU threads */ __u64 kvm_s390_get_cpu_timer(struct kvm_vcpu *vcpu) { + unsigned int seq; __u64 value; - int me; if (unlikely(!vcpu->arch.cputm_enabled)) return vcpu->arch.sie_block->cputm; - me = get_cpu(); /* also protects from TOD sync and vcpu_load/put */ - value = vcpu->arch.sie_block->cputm; - if (likely(me == vcpu->cpu)) { - /* the VCPU itself will always read consistent values */ - value -= get_tod_clock_fast() - vcpu->arch.cputm_start; - } - put_cpu(); + preempt_disable(); /* protect from TOD sync and vcpu_load/put */ + do { + seq = raw_read_seqcount(&vcpu->arch.cputm_seqcount); + /* + * If the writer would ever execute a read in the critical + * section, e.g. in irq context, we have a deadlock. + */ + WARN_ON_ONCE((seq & 1) && smp_processor_id() == vcpu->cpu); + value = vcpu->arch.sie_block->cputm; + /* if cputm_start is 0, accounting is being started/stopped */ + if (likely(vcpu->arch.cputm_start)) + value -= get_tod_clock_fast() - vcpu->arch.cputm_start; + } while (read_seqcount_retry(&vcpu->arch.cputm_seqcount, seq & ~1)); + preempt_enable(); return value; } @@ -1704,6 +1717,7 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, vcpu->arch.local_int.float_int = &kvm->arch.float_int; vcpu->arch.local_int.wq = &vcpu->wq; vcpu->arch.local_int.cpuflags = &vcpu->arch.sie_block->cpuflags; + seqcount_init(&vcpu->arch.cputm_seqcount); rc = kvm_vcpu_init(vcpu, kvm, id); if (rc) |