mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-15 08:14:15 +08:00
ffad018cc0
Added documentation for diag 501, stating that no subfunctions are provided and no parameters are used. Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com> Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
83 lines
2.8 KiB
Plaintext
83 lines
2.8 KiB
Plaintext
The s390 DIAGNOSE call on KVM
|
|
=============================
|
|
|
|
KVM on s390 supports the DIAGNOSE call for making hypercalls, both for
|
|
native hypercalls and for selected hypercalls found on other s390
|
|
hypervisors.
|
|
|
|
Note that bits are numbered as by the usual s390 convention (most significant
|
|
bit on the left).
|
|
|
|
|
|
General remarks
|
|
---------------
|
|
|
|
DIAGNOSE calls by the guest cause a mandatory intercept. This implies
|
|
all supported DIAGNOSE calls need to be handled by either KVM or its
|
|
userspace.
|
|
|
|
All DIAGNOSE calls supported by KVM use the RS-a format:
|
|
|
|
--------------------------------------
|
|
| '83' | R1 | R3 | B2 | D2 |
|
|
--------------------------------------
|
|
0 8 12 16 20 31
|
|
|
|
The second-operand address (obtained by the base/displacement calculation)
|
|
is not used to address data. Instead, bits 48-63 of this address specify
|
|
the function code, and bits 0-47 are ignored.
|
|
|
|
The supported DIAGNOSE function codes vary by the userspace used. For
|
|
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
|
|
-----------------------------------------------------
|
|
|
|
If the function code specifies 0x500, various virtio-related functions
|
|
are performed.
|
|
|
|
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).
|
|
|
|
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.
|
|
|
|
Subcode 0 - s390-virtio notification and early console printk
|
|
Handled by userspace.
|
|
|
|
Subcode 1 - s390-virtio reset
|
|
Handled by userspace.
|
|
|
|
Subcode 2 - s390-virtio set status
|
|
Handled by userspace.
|
|
|
|
Subcode 3 - virtio-ccw notification
|
|
Handled by either userspace or KVM (ioeventfd case).
|
|
|
|
General register 2 contains a subchannel-identification word denoting
|
|
the subchannel of the virtio-ccw proxy device to be notified.
|
|
|
|
General register 3 contains the number of the virtqueue to be notified.
|
|
|
|
General register 4 contains a 64bit identifier for KVM usage (the
|
|
kvm_io_bus cookie). If general register 4 does not contain a valid
|
|
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).
|
|
|
|
See also the virtio standard for a discussion of this hypercall.
|
|
|
|
|
|
DIAGNOSE function code 'X'501 - KVM breakpoint
|
|
----------------------------------------------
|
|
|
|
If the function code specifies 0x501, breakpoint functions may be performed.
|
|
This function code is handled by userspace.
|
|
|
|
This diagnose function code has no subfunctions and uses no parameters.
|