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

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> 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>

I'll need focused time to review this one and several latter big patches, which
can't be afforded this week. Will do that next week.

One immediate comment though. Looks below comment is not fixed
which you said is for XENPMU_MODE_ALL:

>
> +        if ( vpmu_mode == XENPMU_MODE_OFF )
> +        {
> +            /*
> +             * Make sure all (non-dom0) VCPUs have unloaded their
> VPMUs. This
> +             * can be achieved by having all physical processors go
> through
> +             * context_switch().
> +             */
> +            ret = vpmu_force_context_switch();
> +            if ( ret )
> +                vpmu_mode = current_mode;
> +        }
> +
> +        spin_unlock(&xenpmu_mode_lock);
> +        break;
> +    }
> +

Thanks
Kevin

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