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Documentation: s390-diag.rst: Make diag500 a generic KVM hypercall

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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 subfunction.

Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Tested-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Link: https://lore.kernel.org/r/20241025141453.1210600-2-david@redhat.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
David Hildenbrand 2024-10-25 16:14:46 +02:00 committed by Heiko Carstens
parent 34fb045edd
commit b7cfc04548
1 changed files with 11 additions and 7 deletions
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18
Documentation/virt/kvm/s390/s390-diag.rst
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@ -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.