Re: [PATCH RFC V4 5/5] Documentation/kvm : Add documentation on Hypercalls and features used for PV spinlock

[Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>]

On 01/16/2012 08:53 AM, Alexander Graf wrote:
>
> On 14.01.2012, at 19:27, Raghavendra K T wrote:
>
>> Add Documentation on CPUID, KVM_CAP_PVLOCK_KICK, and Hypercalls supported.
>>
>> KVM_HC_KICK_CPU  hypercall added to wakeup halted vcpu in
>> paravirtual spinlock enabled guest.
>>
>> KVM_FEATURE_PVLOCK_KICK enables guest to check whether pv spinlock can
>> be enabled in guest. support in host is queried via
>> ioctl(KVM_CHECK_EXTENSION, KVM_CAP_PVLOCK_KICK)
>>
>> A minimal Documentation and template is added for hypercalls.
>>
>> Signed-off-by: Raghavendra K T<raghavendra.kt@linux.vnet.ibm.com>
>> Signed-off-by: Srivatsa Vaddagiri<vatsa@linux.vnet.ibm.com>
>> ---
[...]
>> diff --git a/Documentation/virtual/kvm/hypercalls.txt b/Documentation/virtual/kvm/hypercalls.txt
>> new file mode 100644
>> index 0000000..7872da5
>> --- /dev/null
>> +++ b/Documentation/virtual/kvm/hypercalls.txt
>> @@ -0,0 +1,54 @@
>> +KVM Hypercalls Documentation
>> +===========================

>> +2. KVM_HC_MMU_OP
>> +------------------------
>> +value: 2
>> +Architecture: x86
>> +Purpose: Support MMU operations such as writing to PTE,
>> +flushing TLB, release PT.
>
> This one is deprecated, no? Should probably be mentioned here.

Ok, then may be adding state = deprecated/obsolete/in use (active) may
be good idea.

>
>> +
>> +3. KVM_HC_FEATURES
>> +------------------------
>> +value: 3
>> +Architecture: PPC
>> +Purpose:
>
> Expose hypercall availability to the guest. On x86 you use cpuid to enumerate which hypercalls are available. The natural fit on ppc would be device tree based lookup (which is also what EPAPR dictates), but we also have a second enumeration mechanism that's KVM specific - which is this hypercall.
>

Thanks, will add this. I hope you are OK if I add Signed-off-by: you.

>> +
>> +4. KVM_HC_PPC_MAP_MAGIC_PAGE
>> +------------------------
>> +value: 4
>> +Architecture: PPC
>> +Purpose: To enable communication between the hypervisor and guest there is a
>> +new
>
> It's not new anymore :)
>
>> shared page that contains parts of supervisor visible register state.
>> +The guest can map this shared page using this hypercall.
>
> ... to access its supervisor register through memory.
>

Will update accordingly.

- Raghu