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diff --git a/Documentation/virt/kvm/s390-diag.rst b/Documentation/virt/kvm/s390-diag.rst deleted file mode 100644 index eaac4864d3d6..000000000000 --- a/Documentation/virt/kvm/s390-diag.rst +++ /dev/null @@ -1,86 +0,0 @@ -.. SPDX-License-Identifier: GPL-2.0 - -============================= -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), or a negative - error value, if an internal error occurred. - - 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. |