Re: [PATCH RFC 5/9] xen: Support for VMCALL mem_events

[Razvan Cojocaru <rcojocaru@bitdefender.com>]

On 07/03/2014 09:28 AM, Jan Beulich wrote:
>>>> On 02.07.14 at 18:23, <rcojocaru@bitdefender.com> wrote:
>> On 07/02/2014 07:11 PM, Jan Beulich wrote:
>>>>>> On 02.07.14 at 17:54, <rcojocaru@bitdefender.com> wrote:
>>>>>> --- a/xen/include/public/hvm/params.h
>>>>>> +++ b/xen/include/public/hvm/params.h
>>>>>> @@ -148,6 +148,8 @@
>>>>>>  #define HVM_PARAM_IOREQ_SERVER_PFN 32
>>>>>>  #define HVM_PARAM_NR_IOREQ_SERVER_PAGES 33
>>>>>>  
>>>>>> -#define HVM_NR_PARAMS          34
>>>>>> +#define HVM_PARAM_MEMORY_EVENT_VMCALL 34
>>>>>
>>>>> So why does this (used only as an argument to
>>>>> hvm_memory_event_traps()) need to be settable? I guess the patch
>>>>> description is just too brief.
>>>>
>>>> Settable?
>>>
>>> You must have a reason to make this a HVM param. That reason is
>>> what I'm asking for.
>>
>> I see. I want to be able to enable / disable this type of events. I.e.:
>>
>> if (flags & ENABLE_VMCALL)
>>     xc_set_hvm_param(xci, domain, HVM_PARAM_MEMORY_EVENT_VMCALL,
>>                      HVMPME_mode_sync);
>>
>> from the application, via libxc.
> 
> But hvm_memory_event_vmcall() simply uses the value, whether or
> not it got set. And if the receiver of the event has to anyway deal
> with instances it didn't enable, then it needs to do filtering anyway,
> and hence there's little point in making configurable the exact value
> being passed back up.

You're right, I see your point. I'll either handle it in do_hvm_op() as
well or remove it completely.


Thanks,
Razvan Cojocaru