From: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx> Thanks Alex for KVM_HC_FEATURES inputs and Jan for VAPIC_POLL_IRQ, and Peter (HPA) for suggesting hypercall ABI addition. Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx> --- Please have a closer look at Hypercall ABI newly added Changes since last post: - Added hypercall ABI (Peter) - made KVM_HC_VAPIC_POLL_IRQ active explicitly (Randy) TODO: We need to add history details of each hypercall as suggested by HPA, which I could not trace easily. Hope it is easy for hypercall authors Documentation/virtual/hypercalls.txt | 71 ++++++++++++++++++++++++++++++++++ 1 files changed, 71 insertions(+), 0 deletions(-) create mode 100644 Documentation/virtual/hypercalls.txt diff --git a/Documentation/virtual/hypercalls.txt b/Documentation/virtual/hypercalls.txt new file mode 100644 index 0000000..caffc08 --- /dev/null +++ b/Documentation/virtual/hypercalls.txt @@ -0,0 +1,71 @@ +Hypercall ABI: +============= +A brief look at calling conventions of X86, S390 and PPC +X86: + KVM Hypercalls have a three-byte sequence of either the vmrun or the vmmrun + instruction. The hypervisor can replace it with instructions that are + guaranteed to be supported. + + Up to four arguments may be passed in rbx, rcx, rdx, and rsi respectively. + The hypercall number should be placed in rax and the return value will be + placed in rax. No other registers will be clobbered unless explicitly stated + by the particular hypercall. + +S390: + R2-R7 are used for parameters 1-6. In addition, R1 is used for hypercall + number. The return value is written to R2. + + S390 uses diagnose instruction as hypercall (0x500) along with hypercall + number in R1. + + PoewerPC: + It uses R3-R10 and hypercall number in R11. R4-R11 are used as output registers. + Return value is placed in R3. + + KVM hypercalls uses 4 byte opcode, that are patched with 'hypercall-instructions' + property inside the device tree's /hypervisor node. + For more information refer to Documentation/virtual/kvm/ppc-pv.txt + +KVM Hypercalls Documentation +=========================== +The template for each hypercall is: +1. Hypercall name, value. +2. Architecture(s) +3. Status (deprecated, obsolete, active) +4. Purpose + +1. KVM_HC_VAPIC_POLL_IRQ +------------------------ +Value: 1 +Architecture: x86 +Status: active +Purpose: Trigger guest exit so that the host can check for pending +interrupts on reentry. + +2. KVM_HC_MMU_OP +------------------------ +Value: 2 +Architecture: x86 +Status: deprecated. +Purpose: Support MMU operations such as writing to PTE, +flushing TLB, release PT. + +3. KVM_HC_FEATURES +------------------------ +Value: 3 +Architecture: PPC +Status: active +Purpose: Expose hypercall availability to the guest. On x86 platforms, cpuid +used to enumerate which hypercalls are available. On PPC, either device tree +based lookup ( which is also what EPAPR dictates) OR KVM specific enumeration +mechanism (which is this hypercall) can be used. + +4. KVM_HC_PPC_MAP_MAGIC_PAGE +------------------------ +Value: 4 +Architecture: PPC +Status: active +Purpose: To enable communication between the hypervisor and guest there is a +shared page that contains parts of supervisor visible register state. +The guest can map this shared page to access its supervisor register through +memory using this hypercall. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
