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

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 09/30/2014 08:48 PM, Tian, Kevin wrote:
> > From: Boris Ostrovsky [mailto:boris.ostrovsky@xxxxxxxxxx]
> > 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@xxxxxxxxxx>
> > Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> In general it's OK to me:
> Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>
>
> 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


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