Re: [Xen-devel] [PATCH for-4.12] x86/vpmu: Improve documentation and parsing for vpmu=

[Juergen Gross <jgross@xxxxxxxx>]

On 04/02/2019 17:06, Jan Beulich wrote:
>>>> On 04.02.19 at 15:58, <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 04/02/2019 14:44, Jan Beulich wrote:
>>>>>> On 04.02.19 at 15:22, <andrew.cooper3@xxxxxxxxxx> wrote:
>>>> On 04/02/2019 13:53, Jan Beulich wrote:
>>>>>>>> On 04.02.19 at 12:41, <andrew.cooper3@xxxxxxxxxx> wrote:
>>>>>> @@ -64,37 +54,37 @@ static DEFINE_PER_CPU(struct vcpu *, last_vcpu);
>>>>>>  static int __init parse_vpmu_params(const char *s)
>>>>>>  {
>>>>>>      const char *ss;
>>>>>> +    int rc = 0, val;
>>>>>> +
>>>>>> +    do {
>>>>>> +        ss = strchr(s, ',');
>>>>>> +        if ( !ss )
>>>>>> +            ss = strchr(s, '\0');
>>>>>> +
>>>>>> +        if ( (val = parse_bool(s, ss)) >= 0 )
>>>>>> +            opt_vpmu_enabled = val;
>>>>>> +        else if ( !cmdline_strcmp(s, "bts") )
>>>>>> +            vpmu_features |= XENPMU_FEATURE_INTEL_BTS;
>>>>>> +        else if ( !cmdline_strcmp(s, "ipc") )
>>>>>> +            vpmu_features |= XENPMU_FEATURE_IPC_ONLY;
>>>>>> +        else if ( !cmdline_strcmp(s, "arch") )
>>>>>> +            vpmu_features |= XENPMU_FEATURE_ARCH_ONLY;
>>>>>> +        else
>>>>>> +            rc = -EINVAL;
>>>>>>  
>>>>>> -    switch ( parse_bool(s, NULL) )
>>>>>> -    {
>>>>>> -    case 0:
>>>>>> -        break;
>>>>>> -    default:
>>>>>> -        do {
>>>>>> -            ss = strchr(s, ',');
>>>>>> -            if ( !ss )
>>>>>> -                ss = strchr(s, '\0');
>>>>>> -
>>>>>> -            if ( !cmdline_strcmp(s, "bts") )
>>>>>> -                vpmu_features |= XENPMU_FEATURE_INTEL_BTS;
>>>>>> -            else if ( !cmdline_strcmp(s, "ipc") )
>>>>>> -                vpmu_features |= XENPMU_FEATURE_IPC_ONLY;
>>>>>> -            else if ( !cmdline_strcmp(s, "arch") )
>>>>>> -                vpmu_features |= XENPMU_FEATURE_ARCH_ONLY;
>>>>>> -            else
>>>>>> -                return -EINVAL;
>>>>>> +        s = ss + 1;
>>>>>> +    } while ( *ss );
>>>>>> +
>>>>>> +    /* Selecting bts/ipc/arch forces vpmu to enabled. */
>>>>>> +    if ( vpmu_features )
>>>>>> +        opt_vpmu_enabled = true;
>>>>> If you want to retain original behavior, the condition here would need
>>>>> to be "!rc && vpmu_features". It's not clear whether your modification
>>>>> in this regard is intentional.
>>>> Oh - that wasn't intentional.
>>>>
>>>> An alternative, now I think about it, is to just have the <bool>=false
>>>> case clear vpmu_features.  This is new behaviour, but it is more
>>>> consistent with how other options work, and it wasn't expressable before.
>>> Generally - yes. But what would e.g. "vpmu=off,ipc" end up doing in
>>> your new model?
>>
>> The use of vpmu_features is somewhat weird.  "bts" acts as an extra
>> feature on top of "generally on", whereas "ipc" and "arch" act as
>> restrictions on top of "generally on".
> 
> Okay let's go that route then.

Release-acked-by: Juergen Gross <jgross@xxxxxxxx>


Juergen

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