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Re: [Xen-devel] [PATCH v5 3/6] xen/PMU: Initialization code for Xen PMU

On 07/02/2015 12:21 PM, David Vrabel wrote:
On 02/07/15 15:53, Boris Ostrovsky wrote:
Map shared data structure that will hold CPU registers, VPMU context,
V/PCPU IDs of the CPU interrupted by PMU interrupt. Hypervisor fills
this information in its handler and passes it to the guest for further

Set up PMU VIRQ.

Now that perf infrastructure will assume that PMU is available on a PV
guest we need to be careful and make sure that accesses via RDPMC
instruction don't cause fatal traps by the hypervisor. Provide a nop
RDPMC handler.

For the same reason avoid issuing a warning on a write to APIC's LVTPC.

Both of these will be made functional in later patches.
+               rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
+                                            xen_pmu_irq_handler,
+                                            IRQF_PERCPU|IRQF_NOBALANCING,
+                                            pmu_name, NULL);
If you bind a VIRQ as IRQF_PERCPU it can only be safely unbound on the
CPU it is bound to (because the percpu handler does not take the

This is a true per-cpu VIRQ and we only unbind it on cpu_die() path so I think IRQF_PERCPU should be safe, no? (it behaves similar to VIRQ_TIMER in how/when it is unbound).


Otherwise, Reviewed-by: David Vrabel <david.vrabel@xxxxxxxxxx>


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