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Commit bda343ef authored by David Hildenbrand's avatar David Hildenbrand Committed by Christian Borntraeger
Browse files

KVM: s390: prevent sleep duration underflows in handle_wait() 



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: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Acked-by: default avatarCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: default avatarDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
parent 8c0a7ce6

arch/s390/kvm/interrupt.c

+7 −1
Original line number Diff line number Diff line
@@ -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: