On Tue, 18 Dec 2018 14:20:34 +0100 Cornelia Huck <cohuck@xxxxxxxxxx> wrote: > If something goes wrong in the kvm io bus handling, the virtio-ccw > diagnose may return a negative error value in the cookie gpr. > > Document this. > > Signed-off-by: Cornelia Huck <cohuck@xxxxxxxxxx> > --- > > Even if the virtio spec is the correct place to specify what diag 500 > subcode 3 does, we also should mention here that the cookie may be > an error. > > --- > Documentation/virtual/kvm/s390-diag.txt | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/Documentation/virtual/kvm/s390-diag.txt b/Documentation/virtual/kvm/s390-diag.txt > index 48c4921794ed..7c52e5f8b210 100644 > --- a/Documentation/virtual/kvm/s390-diag.txt > +++ b/Documentation/virtual/kvm/s390-diag.txt > @@ -68,7 +68,8 @@ Subcode 3 - virtio-ccw notification > identifier, it is ignored. > > After completion of the DIAGNOSE call, general register 2 may contain > - a 64bit identifier (in the kvm_io_bus cookie case). > + a 64bit identifier (in the kvm_io_bus cookie case), or a negative > + error value, if an internal error occurred. > > See also the virtio standard for a discussion of this hypercall. > Queued.
