KVM: s390: consider epoch index on TOD clock syncs (1575767e) · Commits · 戴 / test

For now, we don't take care of over/underflows. Especially underflows are critical: Assume the epoch is currently 0 and we get a sync request for delta=1, meaning the TOD is moved forward by 1 and we have to fix it up by subtracting 1 from the epoch. Right now, this will leave the epoch index untouched, resulting in epoch=-1, epoch_idx=0, which is wrong. We have to take care of over and underflows, also for the VSIE case. So let's factor out calculation into a separate function. Signed-off-by:

David Hildenbrand <david@redhat.com> Message-Id: <20180207114647.6220-5-david@redhat.com> Reviewed-by:

Christian Borntraeger <borntraeger@de.ibm.com> Fixes: ("KVM: s390: Multiple Epoch Facility support") Cc: stable@vger.kernel.org Signed-off-by:

Christian Borntraeger <borntraeger@de.ibm.com> [use u8 for idx]

arch/s390/kvm/kvm-s390.c

+29 −3

Original line number	Diff line number	Diff line
		@@ -179,6 +179,28 @@ int kvm_arch_hardware_enable(void)
		static void kvm_gmap_notifier(struct gmap *gmap, unsigned long start,
		unsigned long end);

		static void kvm_clock_sync_scb(struct kvm_s390_sie_block *scb, u64 delta)
		{
		u8 delta_idx = 0;

		/*
		* The TOD jumps by delta, we have to compensate this by adding
		* -delta to the epoch.
		*/
		delta = -delta;

		/* sign-extension - we're adding to signed values below */
		if ((s64)delta < 0)
		delta_idx = -1;

		scb->epoch += delta;
		if (scb->ecd & ECD_MEF) {
		scb->epdx += delta_idx;
		if (scb->epoch < delta)
		scb->epdx += 1;
		}
		}

		/*
		* This callback is executed during stop_machine(). All CPUs are therefore
		* temporarily stopped. In order not to change guest behavior, we have to
		@@ -194,13 +216,17 @@ static int kvm_clock_sync(struct notifier_block *notifier, unsigned long val,
		unsigned long long *delta = v;

		list_for_each_entry(kvm, &vm_list, vm_list) {
		kvm->arch.epoch -= *delta;
		kvm_for_each_vcpu(i, vcpu, kvm) {
		vcpu->arch.sie_block->epoch -= *delta;
		kvm_clock_sync_scb(vcpu->arch.sie_block, *delta);
		if (i == 0) {
		kvm->arch.epoch = vcpu->arch.sie_block->epoch;
		kvm->arch.epdx = vcpu->arch.sie_block->epdx;
		}
		if (vcpu->arch.cputm_enabled)
		vcpu->arch.cputm_start += *delta;
		if (vcpu->arch.vsie_block)
		vcpu->arch.vsie_block->epoch -= *delta;
		kvm_clock_sync_scb(vcpu->arch.vsie_block,
		*delta);
		}
		}
		return NOTIFY_OK;

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