Re: [PATCH v12 for-xen-4.5 11/20] x86/VPMU: Interface for setting PMU mode and flags

[Boris Ostrovsky <boris.ostrovsky@oracle.com>]

On 09/30/2014 08:48 PM, Tian, Kevin wrote:
>> From: Boris Ostrovsky [mailto:boris.ostrovsky@oracle.com]
>> Sent: Thursday, September 25, 2014 12:29 PM
>>
>> Add runtime interface for setting PMU mode and flags. Three main modes are
>> provided:
>> * XENPMU_MODE_OFF:  PMU is not virtualized
>> * XENPMU_MODE_SELF: Guests can access PMU MSRs and receive PMU
>> interrupts.
>> * XENPMU_MODE_HV: Same as XENPMU_MODE_SELF for non-proviledged
>> guests, dom0
>>    can profile itself and the hypervisor.
>>
>> Note that PMU modes are different from what can be provided at Xen's boot
>> line
>> with 'vpmu' argument. An 'off' (or '0') value is equivalent to
>> XENPMU_MODE_OFF.
>> Any other value, on the other hand, will cause VPMU mode to be set to
>> XENPMU_MODE_SELF during boot.
>>
>> For feature flags only Intel's BTS is currently supported.
>>
>> Mode and flags are set via HYPERVISOR_xenpmu_op hypercall.
>>
>> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
>> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> In general it's OK to me:
> Acked-by: Kevin Tian <kevin.tian@intel.com>
>
> Just a small comment:
>
>> +static void vpmu_sched_checkin(unsigned long unused)
>> +{
>> +    atomic_inc(&vpmu_sched_counter);
>> +}
>> +
>> +static int vpmu_force_context_switch(void)
>> +{
>> +    unsigned i, j, allbutself_num, mycpu;
>> +    static s_time_t start, now;
> any reason of such static variables when there's no continuation any more?

No reason at all. They are gone in v13.

Thanks.
-boris