diff options
Diffstat (limited to 'Documentation/virtual')
| -rw-r--r-- | Documentation/virtual/kvm/hypercalls.txt | 3 | ||||
| -rw-r--r-- | Documentation/virtual/kvm/s390-diag.txt | 80 |
2 files changed, 83 insertions, 0 deletions
diff --git a/Documentation/virtual/kvm/hypercalls.txt b/Documentation/virtual/kvm/hypercalls.txt index 022198e389d..d922d73efa7 100644 --- a/Documentation/virtual/kvm/hypercalls.txt +++ b/Documentation/virtual/kvm/hypercalls.txt @@ -17,6 +17,9 @@ S390: S390 uses diagnose instruction as hypercall (0x500) along with hypercall number in R1. + For further information on the S390 diagnose call as supported by KVM, + refer to Documentation/virtual/kvm/s390-diag.txt. + PowerPC: It uses R3-R10 and hypercall number in R11. R4-R11 are used as output registers. Return value is placed in R3. diff --git a/Documentation/virtual/kvm/s390-diag.txt b/Documentation/virtual/kvm/s390-diag.txt new file mode 100644 index 00000000000..f1de4fbade1 --- /dev/null +++ b/Documentation/virtual/kvm/s390-diag.txt @@ -0,0 +1,80 @@ +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. |