Re: [Xen-devel] [PATCH v3 11/16] x86/VPMU: Add support for PMU register handling on PV guests

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.01.14 at 16:44, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> wrote:
> On 01/13/2014 09:12 AM, Jan Beulich wrote:
>>>>> On 06.01.14 at 20:24, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> wrote:
>>> @@ -875,7 +875,9 @@ void pv_cpuid(struct cpu_user_regs *regs)
>>>       unsupported:
>>>           a = b = c = d = 0;
>>>           break;
>>> -
>>> +    case 0x0000000a: /* Architectural Performance Monitor Features (Intel) 
>>> */
>>> +        vpmu_do_cpuid(0xa, &a, &b, &c, &d);
>>> +        break;
>>>       default:
>> Rather than removing a blank line here, you ought to insert a
>> second one so that there's one before _and_ after the added
>> code block.
>>
>> Furthermore the need to pass 0xa as the first argument suggests
>> that you're not in line with the intentions of vpmu_do_cpuid():
>> Either you drop the first parameter from the function, or you get
>> your code in line with the existing caller.
> 
> Not sure I understand the problem. We fill a, b, c and d with HW values 
> for dom0 and then call vpmu_do_cpuid() to adjust them if needed. And 
> whether or not this is needed is based on the first argument.

Did you look at the other call site? Iirc it calls the function for all
input values (and hence the need for the current first parameter
of the function). I take it that the expectation was that further
perfctr related leaves might be added later and/or perfctr code
may need to override more than just leaf 0xa values.

Jan


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