Re: [Xen-devel] [PATCH v15 11/21] x86/VPMU: Interface for setting PMU mode and flags

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 03.12.14 at 21:13, <boris.ostrovsky@xxxxxxxxxx> wrote:
> On 11/27/2014 03:57 AM, Jan Beulich wrote:
>>>>> On 26.11.14 at 15:32, <boris.ostrovsky@xxxxxxxxxx> wrote:
>>> On 11/25/2014 08:49 AM, Jan Beulich wrote:
>>>>>>> On 17.11.14 at 00:07, <boris.ostrovsky@xxxxxxxxxx> wrote:
>>>>> @@ -244,19 +256,19 @@ void vpmu_initialise(struct vcpu *v)
>>>>>        switch ( vendor )
>>>>>        {
>>>>>        case X86_VENDOR_AMD:
>>>>> -        if ( svm_vpmu_initialise(v, opt_vpmu_enabled) != 0 )
>>>>> -            opt_vpmu_enabled = 0;
>>>>> +        if ( svm_vpmu_initialise(v) != 0 )
>>>>> +            vpmu_mode = XENPMU_MODE_OFF;
>>>>>            break;
>>>>>    
>>>>>        case X86_VENDOR_INTEL:
>>>>> -        if ( vmx_vpmu_initialise(v, opt_vpmu_enabled) != 0 )
>>>>> -            opt_vpmu_enabled = 0;
>>>>> +        if ( vmx_vpmu_initialise(v) != 0 )
>>>>> +            vpmu_mode = XENPMU_MODE_OFF;
>>>>>            break;
>>>> So this turns off the vPMU globally upon failure of initializing
>>>> some random vCPU. Why is that? I see this was the case even
>>>> before your entire series, but shouldn't this be fixed _before_
>>>> enhancing the whole thing to support PV/PVH?
>>> Yes, that's probably too strong. Do you want to fix this as an early
>>> patch (before PV(H)) support gets in? I'd rather do it in the patch that
>>> moves things into initcalls.
>> Yes, I think this should be fixed in a prereq patch, thus allowing it
>> to be easily backported if so desired.
> 
> I started to make this change and then I realized that the next patch 
> (12/21) is actually already taking care of this problem: most of the 
> *_vpmu_initialise() will be executed as initcalls during host boot and 
> if any of those fail then we do want to disable VPMU globally (those 
> failures would not be VCPU-specific).

Funny that you say that - it was actually while reviewing that next
patch when I made that observation: svm_vpmu_initialise() get a
-ENOMEM return _added_ there for example, which is contrary to
what I asked for above.

Jan


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