linux/Documentation/virtual/kvm/hypercalls.txt
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   1Linux KVM Hypercall:
   2===================
   3X86:
   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.
   7
   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.
  12
  13S390:
  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.
  16
  17  S390 uses diagnose instruction as hypercall (0x500) along with hypercall
  18  number in R1.
  19
  20 PowerPC:
  21  It uses R3-R10 and hypercall number in R11. R4-R11 are used as output registers.
  22  Return value is placed in R3.
  23
  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
  27
  28KVM Hypercalls Documentation
  29===========================
  30The template for each hypercall is:
  311. Hypercall name.
  322. Architecture(s)
  333. Status (deprecated, obsolete, active)
  344. Purpose
  35
  361. KVM_HC_VAPIC_POLL_IRQ
  37------------------------
  38Architecture: x86
  39Status: active
  40Purpose: Trigger guest exit so that the host can check for pending
  41interrupts on reentry.
  42
  432. KVM_HC_MMU_OP
  44------------------------
  45Architecture: x86
  46Status: deprecated.
  47Purpose: Support MMU operations such as writing to PTE,
  48flushing TLB, release PT.
  49
  503. KVM_HC_FEATURES
  51------------------------
  52Architecture: PPC
  53Status: active
  54Purpose: Expose hypercall availability to the guest. On x86 platforms, cpuid
  55used to enumerate which hypercalls are available. On PPC, either device tree
  56based lookup ( which is also what EPAPR dictates) OR KVM specific enumeration
  57mechanism (which is this hypercall) can be used.
  58
  594. KVM_HC_PPC_MAP_MAGIC_PAGE
  60------------------------
  61Architecture: PPC
  62Status: active
  63Purpose: To enable communication between the hypervisor and guest there is a
  64shared page that contains parts of supervisor visible register state.
  65The guest can map this shared page to access its supervisor register through
  66memory using this hypercall.
  67
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