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

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 <redacted>
---
 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;
 	} else if (rc != H_SUCCESS) {
 		dev_err(&p->pdev->dev,
 			"Failed to query performance stats, Err:%lld\n", rc);

-- 
2.30.2

On Wed, Apr 14, 2021 at 06:10:26PM +0530, Vaibhav Jain wrote:

Is this because of a disabled feature or because of permissions?

Ira

 	} else if (rc != H_SUCCESS) {
 		dev_err(&p->pdev->dev,
 			"Failed to query performance stats, Err:%lld\n", rc);
-- 
2.30.2

Thanks for looking into this patch Ira,

Ira Weiny [off-list ref] writes:

On Wed, Apr 14, 2021 at 06:10:26PM +0530, Vaibhav Jain wrote:

quoted

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 <redacted>
---
 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;

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.

Ira

quoted

 	} else if (rc != H_SUCCESS) {
 		dev_err(&p->pdev->dev,
 			"Failed to query performance stats, Err:%lld\n", rc);
-- 
2.30.2

-- 
Cheers
~ Vaibhav

On Wed, Apr 14, 2021 at 09:51:40PM +0530, Vaibhav Jain wrote:

Thanks for looking into this patch Ira,

Ira Weiny [off-list ref] writes:

quoted

On Wed, Apr 14, 2021 at 06:10:26PM +0530, Vaibhav Jain wrote:

quoted

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 <redacted>
---
 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;

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'?

Ira

On Wed, Apr 14, 2021 at 5:40 AM Vaibhav Jain [off-list ref] wrote:

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

Thanks for looking into this Dan,

Dan Williams [off-list ref] writes:

On Wed, Apr 14, 2021 at 5:40 AM Vaibhav Jain [off-list ref] wrote:

quoted

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 <redacted>
---
 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.

Currently this error message is only reported during probe of the
nvdimm. So userspace cannot directly spam kernel log.

The callsite for this function in papr_scm_nvdimm_init() doesnt handle
specific error codes. Instead in case of an error it only reports that
"Dimm performance stats are unavailable". The log message just
preceeding that mentions the real cause of failure. Thats why just
returning -EPERM wont be usefui.

Alternatively I can update papr_scm_nvdimm_init() to report the error
code returned from drc_pmem_query_stats().

-- 
Cheers
~ Vaibhav

Ira Weiny [off-list ref] writes:

On Wed, Apr 14, 2021 at 09:51:40PM +0530, Vaibhav Jain wrote:

quoted

Thanks for looking into this patch Ira,

Ira Weiny [off-list ref] writes:

quoted

On Wed, Apr 14, 2021 at 06:10:26PM +0530, Vaibhav Jain wrote:

quoted

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 <redacted>
---
 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;

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.

Will update the warn message in v2.

Ira

-- 
Cheers
~ Vaibhav

On Thu, Apr 15, 2021 at 4:44 AM Vaibhav Jain [off-list ref] wrote:

Thanks for looking into this Dan,

Dan Williams [off-list ref] writes:

quoted

On Wed, Apr 14, 2021 at 5:40 AM Vaibhav Jain [off-list ref] wrote:

quoted

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 <redacted>
---
 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.

Currently this error message is only reported during probe of the
nvdimm. So userspace cannot directly spam kernel log.

Oh, ok, I saw things like papr_pdsm_fuel_gauge() in the call stack and
thought this was reachable through an ioctl. Sorry for the noise.

On 4/15/21 5:18 PM, Vaibhav Jain wrote:

Ira Weiny [off-list ref] writes:

quoted

On Wed, Apr 14, 2021 at 09:51:40PM +0530, Vaibhav Jain wrote:

quoted

Thanks for looking into this patch Ira,

Ira Weiny [off-list ref] writes:

quoted

On Wed, Apr 14, 2021 at 06:10:26PM +0530, Vaibhav Jain wrote:

quoted

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 <redacted>
---
 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;

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<redacted>

Thanks,
Kajol Jain

Will update the warn message in v2.

quoted

Ira