Re: [Xen-devel] [PATCH v3 05/16] x86/VPMU: Handle APIC_LVTPC accesses

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.01.14 at 16:04, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> wrote:
> On 01/13/2014 08:28 AM, Jan Beulich wrote:
>>>>> On 06.01.14 at 20:24, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> wrote:
>>> Update APIC_LVTPC vector when HVM guest writes to it.
>>>
>>> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> 
> ...
> 
>>> +void vpmu_lvtpc_update(uint32_t val)
>>> +{
>>> +    struct vpmu_struct *vpmu = vcpu_vpmu(current);
>>> +
>>> +    vpmu->hw_lapic_lvtpc = PMU_APIC_VECTOR | (val & APIC_LVT_MASKED);
>>> +    apic_write(APIC_LVTPC, vpmu->hw_lapic_lvtpc);
>>> +}
>>> +
>>>   int vpmu_do_wrmsr(unsigned int msr, uint64_t msr_content)
>>>   {
>>>       struct vpmu_struct *vpmu = vcpu_vpmu(current);
>>> @@ -227,19 +235,21 @@ void vpmu_initialise(struct vcpu *v)
>>>       case X86_VENDOR_AMD:
>>>           if ( svm_vpmu_initialise(v, opt_vpmu_enabled) != 0 )
>>>               opt_vpmu_enabled = 0;
>>> -        break;
>>> +        return;
>>>   
>>>       case X86_VENDOR_INTEL:
>>>           if ( vmx_vpmu_initialise(v, opt_vpmu_enabled) != 0 )
>>>               opt_vpmu_enabled = 0;
>>> -        break;
>>> +        return;
>>>   
>>>       default:
>>>           printk("VPMU: Initialization failed. "
>>>                  "Unknown CPU vendor %d\n", vendor);
>>>           opt_vpmu_enabled = 0;
>>> -        break;
>>> +        return;
>>>       }
>>> +
>>> +    vpmu->hw_lapic_lvtpc = PMU_APIC_VECTOR | APIC_LVT_MASKED;
>>>   }
>> So what is this good for? All code paths above use "return" now,
>> hence how would execution get here?
> 
> Yes, it shouldn't be here. I could move it up but since we are now 
> updating LVTPC explicitly when a guest is writing APIC I think I can 
> just drop it altogether.

As long as the mask bit gets properly set somewhere, not adding
it here or anywhere else seems fine to me.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel