@@ -35,20 +35,24 @@ DIAGNOSE function codes not specific to KVM, please refer to the
documentation for the s390 hypervisors defining them.
-DIAGNOSE function code 'X'500' - KVM virtio functions
------------------------------------------------------
+DIAGNOSE function code 'X'500' - KVM functions
+----------------------------------------------
-If the function code specifies 0x500, various virtio-related functions
-are performed.
+If the function code specifies 0x500, various KVM-specific functions
+are performed, including virtio functions.
-General register 1 contains the virtio subfunction code. Supported
-virtio subfunctions depend on KVM's userspace. Generally, userspace
-provides either s390-virtio (subcodes 0-2) or virtio-ccw (subcode 3).
+General register 1 contains the subfunction code. Supported subfunctions
+depend on KVM's userspace. Regarding virtio subfunctions, generally
+userspace provides either s390-virtio (subcodes 0-2) or virtio-ccw
+(subcode 3).
Upon completion of the DIAGNOSE instruction, general register 2 contains
the function's return code, which is either a return code or a subcode
specific value.
+If the specified subfunction is not supported, a SPECIFICATION exception
+will be triggered.
+
Subcode 0 - s390-virtio notification and early console printk
Handled by userspace.
Let's make it a generic KVM hypercall, allowing other subfunctions to be more independent of virtio. While at it, document that unsupported/unimplemented subfunctions result in a SPECIFICATION exception. This is a preparation for documenting a new hypercall. Signed-off-by: David Hildenbrand <david@redhat.com> --- Documentation/virt/kvm/s390/s390-diag.rst | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-)