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* [PATCH v3] powerpc/papr_scm: Reduce error severity if nvdimm stats inaccessible
@ 2021-05-08  4:36 Vaibhav Jain
  2021-05-08 15:11 ` Ira Weiny
  2021-05-19  7:06 ` kajoljain
  0 siblings, 2 replies; 3+ messages in thread
From: Vaibhav Jain @ 2021-05-08  4:36 UTC (permalink / raw)
  To: linuxppc-dev, linux-nvdimm
  Cc: Vaibhav Jain, Aneesh Kumar K . V, Michael Ellerman

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

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 <>

* Return EOPNOTSUPP error in case of H_UNSUPPORTED [ Ira ]
* Return EPERM in case of H_AUTHORITY [ Ira ]
* Updated patch description

* 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,
 			"Unknown performance stats, Err:0x%016lX\n", ret[0]);
 		return -ENOENT;
+	} else if (rc == H_AUTHORITY) {
+		dev_info(&p->pdev->dev,
+			 "Permission denied while accessing performance stats");
+		return -EPERM;
+	} else if (rc == H_UNSUPPORTED) {
+		dev_dbg(&p->pdev->dev, "Performance stats unsupported\n");
+		return -EOPNOTSUPP;
 	} else if (rc != H_SUCCESS) {
 			"Failed to query performance stats, Err:%lld\n", rc);
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end of thread, other threads:[~2021-05-19  7:06 UTC | newest]

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2021-05-08  4:36 [PATCH v3] powerpc/papr_scm: Reduce error severity if nvdimm stats inaccessible Vaibhav Jain
2021-05-08 15:11 ` Ira Weiny
2021-05-19  7:06 ` kajoljain

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