From 60417fcc2b0235dfe3dcd589c56dbe3ea1a64c54 Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Tue, 29 Sep 2015 16:20:36 +0200 Subject: [PATCH] KVM: s390: factor out reading of the guest TOD clock Let's factor this out and always use get_tod_clock_fast() when reading the guest TOD. STORE CLOCK FAST does not do serialization and, therefore, might result in some fuzziness between different processors in a way that subsequent calls on different CPUs might have time stamps that are earlier. This semantics is fine though for all KVM use cases. To make it obvious that the new function has STORE CLOCK FAST semantics we name it kvm_s390_get_tod_clock_fast. With this patch, we only have a handful of places were we have to care about STP sync (using preempt_disable() logic). Reviewed-by: Christian Borntraeger Signed-off-by: David Hildenbrand Signed-off-by: Christian Borntraeger --- arch/s390/kvm/interrupt.c | 15 +++------------ arch/s390/kvm/kvm-s390.c | 4 +--- arch/s390/kvm/kvm-s390.h | 10 ++++++++++ 3 files changed, 14 insertions(+), 15 deletions(-) diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c index a8be542b9cb0..373e32346d68 100644 --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -69,13 +69,8 @@ static int ckc_interrupts_enabled(struct kvm_vcpu *vcpu) static int ckc_irq_pending(struct kvm_vcpu *vcpu) { - preempt_disable(); - if (!(vcpu->arch.sie_block->ckc < - get_tod_clock_fast() + vcpu->arch.sie_block->epoch)) { - preempt_enable(); + if (vcpu->arch.sie_block->ckc >= kvm_s390_get_tod_clock_fast(vcpu->kvm)) return 0; - } - preempt_enable(); return ckc_interrupts_enabled(vcpu); } @@ -851,9 +846,7 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu) goto no_timer; } - preempt_disable(); - now = get_tod_clock_fast() + vcpu->arch.sie_block->epoch; - preempt_enable(); + now = kvm_s390_get_tod_clock_fast(vcpu->kvm); sltime = tod_to_ns(vcpu->arch.sie_block->ckc - now); /* underflow */ @@ -892,9 +885,7 @@ enum hrtimer_restart kvm_s390_idle_wakeup(struct hrtimer *timer) u64 now, sltime; vcpu = container_of(timer, struct kvm_vcpu, arch.ckc_timer); - preempt_disable(); - now = get_tod_clock_fast() + vcpu->arch.sie_block->epoch; - preempt_enable(); + now = kvm_s390_get_tod_clock_fast(vcpu->kvm); sltime = tod_to_ns(vcpu->arch.sie_block->ckc - now); /* diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 87bd602f326c..618c85411a51 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -568,9 +568,7 @@ static int kvm_s390_get_tod_low(struct kvm *kvm, struct kvm_device_attr *attr) { u64 gtod; - preempt_disable(); - gtod = get_tod_clock() + kvm->arch.epoch; - preempt_enable(); + gtod = kvm_s390_get_tod_clock_fast(kvm); if (copy_to_user((void __user *)attr->addr, >od, sizeof(gtod))) return -EFAULT; VM_EVENT(kvm, 3, "QUERY: TOD base: 0x%llx\n", gtod); diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h index cc15ea3a150e..1e70e00d3c5e 100644 --- a/arch/s390/kvm/kvm-s390.h +++ b/arch/s390/kvm/kvm-s390.h @@ -271,6 +271,16 @@ static inline void kvm_s390_vcpu_unblock_all(struct kvm *kvm) kvm_s390_vcpu_unblock(vcpu); } +static inline u64 kvm_s390_get_tod_clock_fast(struct kvm *kvm) +{ + u64 rc; + + preempt_disable(); + rc = get_tod_clock_fast() + kvm->arch.epoch; + preempt_enable(); + return rc; +} + /** * kvm_s390_inject_prog_cond - conditionally inject a program check * @vcpu: virtual cpu -- 2.20.1