From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Borntraeger Subject: [PATCH/RFC 05/21] KVM: s390: prevent sleep duration underflows in handle_wait() Date: Thu, 15 Jan 2015 14:43:18 +0100 Message-ID: <1421329414-76826-6-git-send-email-borntraeger@de.ibm.com> References: <1421329414-76826-1-git-send-email-borntraeger@de.ibm.com> Return-path: In-Reply-To: <1421329414-76826-1-git-send-email-borntraeger@de.ibm.com> Sender: kvm-owner@vger.kernel.org List-Archive: List-Post: To: Paolo Bonzini Cc: KVM , linux-s390 , David Hildenbrand , Christian Borntraeger List-ID: From: David Hildenbrand We sometimes get an underflow for the sleep duration, which most likely won't result in the short sleep time we wanted. So let's check for sleep duration underflows and directly continue to run the guest if we get one. Acked-by: Christian Borntraeger Acked-by: Cornelia Huck Signed-off-by: David Hildenbrand Signed-off-by: Christian Borntraeger --- arch/s390/kvm/interrupt.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c index a845e35..5744303 100644 --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -804,14 +804,20 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu) return -EOPNOTSUPP; /* disabled wait */ } - __set_cpu_idle(vcpu); if (!ckc_interrupts_enabled(vcpu)) { VCPU_EVENT(vcpu, 3, "%s", "enabled wait w/o timer"); + __set_cpu_idle(vcpu); goto no_timer; } now = get_tod_clock_fast() + vcpu->arch.sie_block->epoch; sltime = tod_to_ns(vcpu->arch.sie_block->ckc - now); + + /* underflow */ + if (vcpu->arch.sie_block->ckc < now) + return 0; + + __set_cpu_idle(vcpu); hrtimer_start(&vcpu->arch.ckc_timer, ktime_set (0, sltime) , HRTIMER_MODE_REL); VCPU_EVENT(vcpu, 5, "enabled wait via clock comparator: %llx ns", sltime); no_timer: -- 1.9.3