4 KVM Hypercalls have a three-byte sequence of either the vmcall or the vmmcall
5 instruction. The hypervisor can replace it with instructions that are
6 guaranteed to be supported.
8 Up to four arguments may be passed in rbx, rcx, rdx, and rsi respectively.
9 The hypercall number should be placed in rax and the return value will be
10 placed in rax. No other registers will be clobbered unless explicitly stated
11 by the particular hypercall.
14 R2-R7 are used for parameters 1-6. In addition, R1 is used for hypercall
15 number. The return value is written to R2.
17 S390 uses diagnose instruction as hypercall (0x500) along with hypercall
21 It uses R3-R10 and hypercall number in R11. R4-R11 are used as output registers.
22 Return value is placed in R3.
24 KVM hypercalls uses 4 byte opcode, that are patched with 'hypercall-instructions'
25 property inside the device tree's /hypervisor node.
26 For more information refer to Documentation/virtual/kvm/ppc-pv.txt
28 KVM Hypercalls Documentation
29 ===========================
30 The template for each hypercall is:
33 3. Status (deprecated, obsolete, active)
36 1. KVM_HC_VAPIC_POLL_IRQ
37 ------------------------
40 Purpose: Trigger guest exit so that the host can check for pending
41 interrupts on reentry.
44 ------------------------
47 Purpose: Support MMU operations such as writing to PTE,
48 flushing TLB, release PT.
51 ------------------------
54 Purpose: Expose hypercall availability to the guest. On x86 platforms, cpuid
55 used to enumerate which hypercalls are available. On PPC, either device tree
56 based lookup ( which is also what EPAPR dictates) OR KVM specific enumeration
57 mechanism (which is this hypercall) can be used.
59 4. KVM_HC_PPC_MAP_MAGIC_PAGE
60 ------------------------
63 Purpose: To enable communication between the hypervisor and guest there is a
64 shared page that contains parts of supervisor visible register state.
65 The guest can map this shared page to access its supervisor register through
66 memory using this hypercall.
69 ------------------------
72 Purpose: Hypercall used to wakeup a vcpu from HLT state
73 Usage example : A vcpu of a paravirtualized guest that is busywaiting in guest
74 kernel mode for an event to occur (ex: a spinlock to become available) can
75 execute HLT instruction once it has busy-waited for more than a threshold
76 time-interval. Execution of HLT instruction would cause the hypervisor to put
77 the vcpu to sleep until occurence of an appropriate event. Another vcpu of the
78 same guest can wakeup the sleeping vcpu by issuing KVM_HC_KICK_CPU hypercall,
79 specifying APIC ID (a1) of the vcpu to be woken up. An additional argument (a0)
80 is used in the hypercall for future use.