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Diffstat (limited to 'Documentation/virt/kvm/s390/s390-diag.rst')
| -rw-r--r-- | Documentation/virt/kvm/s390/s390-diag.rst | 35 |
1 files changed, 28 insertions, 7 deletions
diff --git a/Documentation/virt/kvm/s390/s390-diag.rst b/Documentation/virt/kvm/s390/s390-diag.rst index ca85f030eb0b..3e4f9e3bef81 100644 --- a/Documentation/virt/kvm/s390/s390-diag.rst +++ b/Documentation/virt/kvm/s390/s390-diag.rst @@ -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. @@ -76,6 +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 ---------------------------------------------- |