Re: [PATCH v3 2/6] xen: add hypercall option to override and restore vcpu affinity

[Dario Faggioli <dario.faggioli@citrix.com>]

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On Thu, 2016-03-03 at 17:48 +0100, Juergen Gross wrote:
> Some hardware (e.g. Dell studio 1555 laptops) require SMIs to be
> called on physical cpu 0 only. Linux drivers like dcdbas or i8k try
> to achieve this by pinning the running thread to cpu 0, but in Dom0
> this is not enough: the vcpu must be pinned to physical cpu 0 via
> Xen, too.
> 
> Add a stable hypercall option SCHEDOP_pin_override to the sched_op
> hypercall to achieve this. It is taking a physical cpu number as
> parameter. If pinning is possible (the calling domain has the
> privilege to make the call and the cpu is available in the domain's
> cpupool) the calling vcpu is pinned to the specified cpu.
>
I would have added the "and the cpu is available in the domain's
cpupool" part in the comment in public headers too, such as:


> --- a/xen/include/public/sched.h
> +++ b/xen/include/public/sched.h
> @@ -118,6 +118,17 @@
>   * With id != 0 and timeout != 0, poke watchdog timer and set new
> timeout.
>   */
>  #define SCHEDOP_watchdog    6
> +
> +/*
> + * Override the current vcpu affinity by pinning it to one physical
> cpu or undo
> + * this override restoring the previous affinity.
> + * @arg == pointer to sched_pin_override_t structure.
> + *
> + * A negative pcpu value will undo a previous pin override and
> restore the
> + * previous cpu affinity.
> + * This call is allowed for the hardware domain only.
", and succeeds only if the specified cpu is available in the domain's
cpupool."

> + */
> +#define SCHEDOP_pin_override 7
>  /* ` } */
>  
>  struct sched_shutdown {
>
In any case, the scheduling part is:

Acked-by: Dario Faggioli <dario.faggioli@citrix.com>

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)


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