Re: [PATCH] powerpc/papr_scm: Reduce error severity if nvdimm stats inaccessible

[Dan Williams <dan.j.williams@intel.com>]

On Wed, Apr 14, 2021 at 5:40 AM Vaibhav Jain <vaibhav@linux.ibm.com> wrote:
>
> Currently drc_pmem_qeury_stats() generates a dev_err in case
> "Enable Performance Information Collection" feature is disabled from
> HMC. The error is of the form below:
>
> papr_scm ibm,persistent-memory:ibm,pmemory@44104001: Failed to query
>          performance stats, Err:-10
>
> This error message confuses users as it implies a possible problem
> with the nvdimm even though its due to a disabled feature.
>
> So we fix this by explicitly handling the H_AUTHORITY error from the
> H_SCM_PERFORMANCE_STATS hcall and generating a warning instead of an
> error, saying that "Performance stats in-accessible".
>
> Fixes: 2d02bf835e57('powerpc/papr_scm: Fetch nvdimm performance stats from PHYP')
> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
> ---
>  arch/powerpc/platforms/pseries/papr_scm.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
> index 835163f54244..9216424f8be3 100644
> --- a/arch/powerpc/platforms/pseries/papr_scm.c
> +++ b/arch/powerpc/platforms/pseries/papr_scm.c
> @@ -277,6 +277,9 @@ static ssize_t drc_pmem_query_stats(struct papr_scm_priv *p,
>                 dev_err(&p->pdev->dev,
>                         "Unknown performance stats, Err:0x%016lX\n", ret[0]);
>                 return -ENOENT;
> +       } else if (rc == H_AUTHORITY) {
> +               dev_warn(&p->pdev->dev, "Performance stats in-accessible");
> +               return -EPERM;

So userspace can spam the kernel log? Why is kernel log message needed
at all? EPERM told the caller what happened.
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