From 8457fdfeb16d307b2acd502cb9224d03174294d2 Mon Sep 17 00:00:00 2001 From: Cornelia Huck Date: Mon, 21 Jan 2019 13:19:42 +0100 Subject: [PATCH] virtio-ccw: diag 500 may return a negative cookie 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. Reviewed-by: Halil Pasic Signed-off-by: Cornelia Huck Signed-off-by: Michael S. Tsirkin --- 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.