4.9-stable review patch. If anyone has any objections, please let me know.
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From: David Hildenbrand david@redhat.com
commit f07afa0462b76a5b9c4f3a43d5ac24fdb86a90c2 upstream.
Even if we don't have extended SCA support, we can have more than 64 CPUs if we don't enable any HW features that might use the SCA entries.
Now, this works just fine, but we missed a return, which is why we would actually store the SCA entries. If we have more than 64 CPUs, this means writing outside of the basic SCA - bad.
Let's fix this. This allows > 64 CPUs when running nested (under vSIE) without random crashes.
Fixes: a6940674c384 ("KVM: s390: allow 255 VCPUs when sca entries aren't used") Reported-by: Christian Borntraeger borntraeger@de.ibm.com Tested-by: Christian Borntraeger borntraeger@de.ibm.com Signed-off-by: David Hildenbrand david@redhat.com Message-Id: 20180306132758.21034-1-david@redhat.com Cc: stable@vger.kernel.org Reviewed-by: Cornelia Huck cohuck@redhat.com Signed-off-by: Christian Borntraeger borntraeger@de.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/s390/kvm/kvm-s390.c | 1 + 1 file changed, 1 insertion(+)
--- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -1601,6 +1601,7 @@ static void sca_add_vcpu(struct kvm_vcpu /* we still need the basic sca for the ipte control */ vcpu->arch.sie_block->scaoh = (__u32)(((__u64)sca) >> 32); vcpu->arch.sie_block->scaol = (__u32)(__u64)sca; + return; } read_lock(&vcpu->kvm->arch.sca_lock); if (vcpu->kvm->arch.use_esca) {