On Wed, 2015-20-05 at 23:34:16 UTC, Sukadev Bhattiprolu wrote:
> >From 955102eacf035b19080dc659a15d9b8fbd8fae7f Mon Sep 17 00:00:00 2001
> From: Sukadev Bhattiprolu <suka...@linux.vnet.ibm.com>
> Date: Tue, 28 Apr 2015 18:47:58 -0400
> Subject: [PATCH 1/1] powerpc/perf/hv-24x7: Check support before registering
> PMU
>
> 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.
>
> Reported-by: Gustavo Luiz Duarte <gu...@br.ibm.com>
> Signed-off-by: Sukadev Bhattiprolu <suka...@linux.vnet.ibm.com>
> ---
>
> Changelog[v2]
> - [Michael Ellerman] Simplify check with bogus parameters.
> ---
> arch/powerpc/perf/hv-24x7.c | 21 +++++++++++++++++++++
> 1 file changed, 21 insertions(+)
>
> diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c
> index ec2eb20..c04a332 100644
> --- a/arch/powerpc/perf/hv-24x7.c
> +++ b/arch/powerpc/perf/hv-24x7.c
> @@ -1268,12 +1268,33 @@ 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.
Comment is wrong.
> + */
> +static bool hv_has_24x7(void)
> +{
> + unsigned long hret;
ret would be fine.
> +
> + hret = h_get_24x7_catalog_page(0, 0, 0);
> +
> + if (hret != H_FUNCTION)
> + pr_err("Error %ld reading catalog, disabling 24x7 PMU\n", hret);
> +
> + return hret == 0;
I don't get what you're doing here.
You check for something other than H_FUNCTION, and print, and then you just
compare against 0. But I wouldn't ever expect that to return 0, because you
passed it bogus args.
The logic should be:
static bool is_24x7_supported(void)
{
if (h_get_24x7_catalog_page(0, 0, 0) == H_FUNCTION)
return false;
return true;
}
> static int hv_24x7_init(void)
> {
> int r;
> unsigned long hret;
> struct hv_perf_caps caps;
>
> + if (!hv_has_24x7())
> + return -ENODEV;
> +
This is no good. You're doing the check, which involves a hcall, before you
even check if you're running with a hypervisor (below).
> if (!firmware_has_feature(FW_FEATURE_LPAR)) {
> pr_debug("not a virtualized system, not enabling\n");
> return -ENODEV;
cheers
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