Re: [PATCH 3/5] booke: define reset and shutdown hcalls

Alexander Graf
2013-07-15T12:26:38Z

On 15.07.2013, at 14:24, Gleb Natapov wrote:

> On Mon, Jul 15, 2013 at 02:21:51PM +0200, Alexander Graf wrote:
>>
>> On 15.07.2013, at 14:15, Gleb Natapov wrote:
>>
>>> On Mon, Jul 15, 2013 at 01:44:46PM +0200, Alexander Graf wrote:
>>>>
>>>> On 15.07.2013, at 13:30, Gleb Natapov wrote:
>>>>
>>>>> On Mon, Jul 15, 2013 at 04:41:17PM +0530, Bharat Bhushan wrote:
>>>>>> KVM_HC_VM_RESET: Requests that the virtual machine be reset.
>>>>>> KVM_HC_VM_SHUTDOWN: Requests that the virtual machine be powered-off/halted.
>>>>>>
>>>>>> These hcalls are handled by guest userspace.
>>>>>>
>>>>>> Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
>>>>>> ---
>>>>>> Documentation/virtual/kvm/hypercalls.txt | 16 ++++++++++++++++
>>>>>> include/uapi/linux/kvm_para.h | 3 ++-
>>>>>> 2 files changed, 18 insertions(+), 1 deletions(-)
>>>>>>
>>>>>> diff --git a/Documentation/virtual/kvm/hypercalls.txt b/Documentation/virtual/kvm/hypercalls.txt
>>>>>> index ea113b5..58acdc1 100644
>>>>>> --- a/Documentation/virtual/kvm/hypercalls.txt
>>>>>> +++ b/Documentation/virtual/kvm/hypercalls.txt
>>>>>> @@ -64,3 +64,19 @@ 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.
>>>>>> +
>>>>>> +5. KVM_HC_VM_RESET
>>>>>> +------------------------
>>>>>> +Architecture: PPC
>>>>>> +Status: active
>>>>>> +Purpose: Requests that the virtual machine be reset. The hcall takes no
>>>>>> +arguments. If successful the hcall does not return. If an error occurs it
>>>>>> +returns EV_INTERNAL.
>>>>>> +
>>>>>> +6. KVM_HC_VM_SHUTDOWN
>>>>>> +------------------------
>>>>>> +Architecture: PPC
>>>>>> +Status: active
>>>>>> +Purpose: Requests that the virtual machine be powered-off/halted.
>>>>>> +The hcall takes no arguments. If successful the hcall does not return.
>>>>>> +If an error occurs it returns EV_INTERNAL.
>>>>>> diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
>>>>>> index cea2c5c..218882d 100644
>>>>>> --- a/include/uapi/linux/kvm_para.h
>>>>>> +++ b/include/uapi/linux/kvm_para.h
>>>>>> @@ -19,7 +19,8 @@
>>>>>> #define KVM_HC_MMU_OP 2
>>>>>> #define KVM_HC_FEATURES 3
>>>>>> #define KVM_HC_PPC_MAP_MAGIC_PAGE 4
>>>>>> -
>>>>>> +#define KVM_HC_VM_RESET 5
>>>>>> +#define KVM_HC_VM_SHUTDOWN 6
>>>>> There is no much sense to share hypercalls between architectures. There
>>>>> is zero probability x86 will implement those for instance (not sure
>>>>> why PPC will want them either instead of emulating devices that do
>>>>> shutdown/reset
>>>>
>>>> Implementing devices gets pretty tricky. Usually all of your devices sit on the SoC with a strictly defined layout. We can randomly shove some device in there, but there's a good chance we're overlapping with another device.
>>>>
>>> I thought we have device trees to sort these things out.
>>
>> For Linux guests, yes :). For proprietary random other guests, no.
>>
> But those can't use hcalls too, no?

Why not? There are customers out there who are more than happy to add functionality, but not change functionality.

Alex