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SubjectRe: [1/1] powerpc/hv-24x7: Check support before registering PMU
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On Thu, 2015-30-04 at 03:04:51 UTC, Sukadev Bhattiprolu wrote:
> We currently try to register the 24x7 PMU unconditionally. Not all
> Power systems support 24x7 counters (eg: Power7). On these systems
> we get a backtrace during boot when trying to register the 24x7 PMU.
>
> Check if the hypervisor supports 24x7 counters before attempting to
> register the 24x7 PMU.

The concept is good, but ..

> diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c
> index ec2eb20..19a59a3 100644
> --- a/arch/powerpc/perf/hv-24x7.c
> +++ b/arch/powerpc/perf/hv-24x7.c
> @@ -1268,12 +1268,44 @@ static struct pmu h_24x7_pmu = {
> .read = h_24x7_event_read,
> };
>
> +/*
> + * Return 1 if we can access the 24x7 counter catalog from the hypervisor.
> + * Return 0 otherwise.
> + */
> +static int hv_has_24x7(void)

bool please

> +{
> + int page_size = 4096;
> + unsigned long hret;
> + void *page;
> + struct hv_24x7_catalog_page_0 *page_0;
> +
> + page_0 = kmalloc(page_size*2, GFP_KERNEL);
> + if (!page_0)
> + return 0;
> +
> + /* buffer for catalog needs to be 4K-aligned */
> + page = (void *)((long)page_0 & (~page_size-1)) + page_size;
> + hret = h_get_24x7_catalog_page(page, 0, 0);
> + kfree(page_0);


It shouldn't need to be this complicated.

You should just be able to do the hcall with bogus args and if you get
H_FUNCTION then 24x7 is not supported.

cheers


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