Commit 5967c17b authored Nov 06, 2015 by David Hildenbrand Committed by Christian Borntraeger Nov 19, 2015

KVM: s390: enable SIMD only when no VCPUs were created



We should never allow to enable/disable any facilities for the guest
when other VCPUs were already created.

kvm_arch_vcpu_(load|put) relies on SIMD not changing during runtime.
If somebody would create and run VCPUs and then decides to enable
SIMD, undefined behaviour could be possible (e.g. vector save area
not being set up).

Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: stable@vger.kernel.org # 4.1+

parent 8005c49d

arch/s390/kvm/kvm-s390.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -342,12 +342,16 @@ static int kvm_vm_ioctl_enable_cap(struct kvm kvm, struct kvm_enable_cap cap)
		r = 0;
		break;
		case KVM_CAP_S390_VECTOR_REGISTERS:
		if (MACHINE_HAS_VX) {
		mutex_lock(&kvm->lock);
		if (atomic_read(&kvm->online_vcpus)) {
		r = -EBUSY;
		} else if (MACHINE_HAS_VX) {
		set_kvm_facility(kvm->arch.model.fac->mask, 129);
		set_kvm_facility(kvm->arch.model.fac->list, 129);
		r = 0;
		} else
		r = -EINVAL;
		mutex_unlock(&kvm->lock);
		VM_EVENT(kvm, 3, "ENABLE: CAP_S390_VECTOR_REGISTERS %s",
		r ? "(not available)" : "(success)");
		break;

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