KVM: s390: use cookies for ioeventfd

Make use of cookies for the virtio ccw notification hypercall to speed up
lookup of devices on the io bus.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
[Small fix to a comment. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
index 3074475..3a74d8a 100644 (file)
--- a/arch/s390/kvm/diag.c
+++ b/arch/s390/kvm/diag.c
@@ -119,12 +119,21 @@ static int __diag_virtio_hypercall(struct kvm_vcpu *vcpu)
         * The layout is as follows:
         * - gpr 2 contains the subchannel id (passed as addr)
         * - gpr 3 contains the virtqueue index (passed as datamatch)
+        * - gpr 4 contains the index on the bus (optionally)
         */
-       ret = kvm_io_bus_write(vcpu->kvm, KVM_VIRTIO_CCW_NOTIFY_BUS,
-                               vcpu->run->s.regs.gprs[2],
-                               8, &vcpu->run->s.regs.gprs[3]);
+       ret = kvm_io_bus_write_cookie(vcpu->kvm, KVM_VIRTIO_CCW_NOTIFY_BUS,
+                                     vcpu->run->s.regs.gprs[2],
+                                     8, &vcpu->run->s.regs.gprs[3],
+                                     vcpu->run->s.regs.gprs[4]);
        srcu_read_unlock(&vcpu->kvm->srcu, idx);
-       /* kvm_io_bus_write returns -EOPNOTSUPP if it found no match. */
+
+       /*
+        * Return cookie in gpr 2, but don't overwrite the register if the
+        * diagnose will be handled by userspace.
+        */
+       if (ret != -EOPNOTSUPP)
+               vcpu->run->s.regs.gprs[2] = ret;
+       /* kvm_io_bus_write_cookie returns -EOPNOTSUPP if it found no match. */
        return ret < 0 ? ret : 0;
 }