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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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?

Jan



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