From 8457fdfeb16d307b2acd502cb9224d03174294d2 Mon Sep 17 00:00:00 2001
From: Cornelia Huck <cohuck@redhat.com>
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 <pasic@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
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 48c4921794edf..7c52e5f8b2103 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.
--
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