Re: [PATCH v3] powerpc/papr_scm: Reduce error severity if nvdimm stats inaccessible
On 5/8/21 10:06 AM, Vaibhav Jain wrote:
> Currently drc_pmem_qeury_stats() generates a dev_err in case
> "Enable Performance Information Collection" feature is disabled from
> HMC or performance stats are not available for an nvdimm. 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/unavailable
> feature. We fix this by explicitly handling the H_AUTHORITY and
> H_UNSUPPORTED errors from the H_SCM_PERFORMANCE_STATS hcall.
>
> In case of H_AUTHORITY error an info message is logged instead of an
> error, saying that "Permission denied while accessing performance
> stats" and an EPERM error is returned back.
>
> In case of H_UNSUPPORTED error we return a EOPNOTSUPP error back from
> drc_pmem_query_stats() indicating that performance stats-query
> operation is not supported on this nvdimm.
>
> Fixes: 2d02bf835e57('powerpc/papr_scm: Fetch nvdimm performance stats from
> PHYP')
> Signed-off-by: Vaibhav Jain
> ---
> Changelog
>
> v3:
> * Return EOPNOTSUPP error in case of H_UNSUPPORTED [ Ira ]
> * Return EPERM in case of H_AUTHORITY [ Ira ]
> * Updated patch description
>
Patch looks good to me.
Reviewed-By: Kajol Jain
Thanks,
Kajol Jain
> v2:
> * Updated the message logged in case of H_AUTHORITY error [ Ira ]
> * Switched from dev_warn to dev_info in case of H_AUTHORITY error.
> * Instead of -EPERM return -EACCESS for H_AUTHORITY error.
> * Added explicit handling of H_UNSUPPORTED error.
> ---
> arch/powerpc/platforms/pseries/papr_scm.c | 7 +++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/powerpc/platforms/pseries/papr_scm.c
> b/arch/powerpc/platforms/pseries/papr_scm.c
> index ef26fe40efb0..e2b69cc3beaf 100644
> --- a/arch/powerpc/platforms/pseries/papr_scm.c
> +++ b/arch/powerpc/platforms/pseries/papr_scm.c
> @@ -310,6 +310,13 @@ static ssize_t drc_pmem_query_stats(struct papr_scm_priv
> *p,
> dev_err(>pdev->dev,
> "Unknown performance stats, Err:0x%016lX\n", ret[0]);
> return -ENOENT;
> + } else if (rc == H_AUTHORITY) {
> + dev_info(>pdev->dev,
> + "Permission denied while accessing performance stats");
> + return -EPERM;
> + } else if (rc == H_UNSUPPORTED) {
> + dev_dbg(>pdev->dev, "Performance stats unsupported\n");
> + return -EOPNOTSUPP;
> } else if (rc != H_SUCCESS) {
> dev_err(>pdev->dev,
> "Failed to query performance stats, Err:%lld\n", rc);
>
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Re: [RFC 1/4] drivers/nvdimm: Add perf interface to expose nvdimm performance stats
On 5/14/21 5:17 PM, Peter Zijlstra wrote:
> On Thu, May 13, 2021 at 05:56:14PM +0530, kajoljain wrote:
>
>> But yes the current read/add/del functions are not adding value. We
>> could add an arch/platform specific function which could handle the
>> capturing of the counter data and do the rest of the operation here,
>> is this approach better?
>
> Right; have your register_nvdimm_pmu() set pmu->{add,del,read} to
> nd_pmu->{add,del,read} directly, don't bother with these intermediates.
> Also you can WARN_ON_ONCE() if any of them are NULL and fail
> registration at that point.
>
Hi Peter,
I will make all required changes and send next version of this patchset
soon.
Thanks,
Kajol Jain
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Re: [RFC 1/4] drivers/nvdimm: Add perf interface to expose nvdimm performance stats
On 5/12/21 10:57 PM, Peter Zijlstra wrote:
> On Wed, May 12, 2021 at 10:08:21PM +0530, Kajol Jain wrote:
>> +static void nvdimm_pmu_read(struct perf_event *event)
>> +{
>> +struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
>> +
>> +/* jump to arch/platform specific callbacks if any */
>> +if (nd_pmu && nd_pmu->read)
>> +nd_pmu->read(event, nd_pmu->dev);
>> +}
>> +
>> +static void nvdimm_pmu_del(struct perf_event *event, int flags)
>> +{
>> +struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
>> +
>> +/* jump to arch/platform specific callbacks if any */
>> +if (nd_pmu && nd_pmu->del)
>> +nd_pmu->del(event, flags, nd_pmu->dev);
>> +}
>> +
>> +static int nvdimm_pmu_add(struct perf_event *event, int flags)
>> +{
>> +struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
>> +
>> +if (flags & PERF_EF_START)
>> +/* jump to arch/platform specific callbacks if any */
>> +if (nd_pmu && nd_pmu->add)
>> +return nd_pmu->add(event, flags, nd_pmu->dev);
>> +return 0;
>> +}
>
> What's the value add here? Why can't you directly set driver pointers? I
> also don't really believe ->{add,del,read} can be optional and still
> have a sane driver.
>
Hi Peter,
The intend for adding these callbacks is to give flexibility to the
arch/platform specific driver code to use its own routine for getting
counter data or specific checks/operations. Arch/platform driver code
would have different method to get the counter data like IBM pseries
nmem* device which uses a hypervisor call(hcall).
But yes the current read/add/del functions are not adding value. We
could add an arch/platform specific function which could handle the
capturing of the counter data and do the rest of the operation here,
is this approach better?
Thanks,
Kajol Jain
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Re: [PATCH] powerpc/papr_scm: Reduce error severity if nvdimm stats inaccessible
On 4/15/21 5:18 PM, Vaibhav Jain wrote:
> Ira Weiny writes:
>
>> On Wed, Apr 14, 2021 at 09:51:40PM +0530, Vaibhav Jain wrote:
>>> Thanks for looking into this patch Ira,
>>>
>>> Ira Weiny writes:
>>>
On Wed, Apr 14, 2021 at 06:10:26PM +0530, Vaibhav Jain 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
> ---
> 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(>pdev->dev,
> "Unknown performance stats, Err:0x%016lX\n", ret[0]);
> return -ENOENT;
> + } else if (rc == H_AUTHORITY) {
> + dev_warn(>pdev->dev, "Performance stats in-accessible");
> + return -EPERM;
Is this because of a disabled feature or because of permissions?
>>>
>>> Its because of a disabled feature that revokes permission for a guest to
>>> retrieve performance statistics.
>>>
>>> The feature is called "Enable Performance Information Collection" and
>>> once disabled the hcall H_SCM_PERFORMANCE_STATS returns an error
>>> H_AUTHORITY indicating that the guest doesn't have permission to retrieve
>>> performance statistics.
>>
>> In that case would it be appropriate to have the error message indicate a
>> permission issue?
>>
>> Something like 'permission denied'?
>
> Yes, Something like "Permission denied while accessing performance
> stats" might be more clear and intuitive.
Hi Vaibhav,
Thanks for the patch. I agree with Ira and above warning message with
"Permission denied" looks more clear.
With that change, patch looks good to me.
Reviewed-By: Kajol Jain
Thanks,
Kajol Jain
>
> Will update the warn message in v2.
>
>>
>> Ira
>>
>
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