[PATCH v3 2/7] Documentation: s390-diag.rst: document diag500(STORAGE LIMIT) subfunction

David Hildenbrand
2024-10-25T14:15:29Z

Let's document our new diag500 subfunction that can be implemented by
userspace.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
Documentation/virt/kvm/s390/s390-diag.rst | 17 +++++++++++++++++
1 file changed, 17 insertions(+)

diff --git a/Documentation/virt/kvm/s390/s390-diag.rst b/Documentation/virt/kvm/s390/s390-diag.rst
index 48a326d41cc0..3e4f9e3bef81 100644
--- a/Documentation/virt/kvm/s390/s390-diag.rst
+++ b/Documentation/virt/kvm/s390/s390-diag.rst
@@ -80,6 +80,23 @@ Subcode 3 - virtio-ccw notification

See also the virtio standard for a discussion of this hypercall.

+Subcode 4 - storage-limit
+ Handled by userspace.
+
+ After completion of the DIAGNOSE call, general register 2 will
+ contain the storage limit: the maximum physical address that might be
+ used for storage throughout the lifetime of the VM.
+
+ The storage limit does not indicate currently usable storage, it may
+ include holes, standby storage and areas reserved for other means, such
+ as memory hotplug or virtio-mem devices. Other interfaces for detecting
+ actually usable storage, such as SCLP, must be used in conjunction with
+ this subfunction.
+
+ Note that the storage limit can be larger, but never smaller than the
+ maximum storage address indicated by SCLP via the "maximum storage
+ increment" and the "increment size".
+

DIAGNOSE function code 'X'501 - KVM breakpoint
----------------------------------------------
--
2.46.1