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>

1 files changed, 13 insertions, 4 deletions

diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
index 3074475c8ae0..3a74d8af0d69 100644
--- 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;
 }