Vaibhav Jain <vaibhav(a)linux.ibm.com> writes:
A warning is reported by the kernel in case perf_stats_show()
an error code. The warning is of the form below:
Failed to query performance stats, Err:-10
dev_attr_show: perf_stats_show+0x0/0x1c0 [papr_scm] returned bad count
fill_read_buffer: dev_attr_show+0x0/0xb0 returned bad count
On investigation it looks like that the compiler is silently truncating the
return value of drc_pmem_query_stats() from 'long' to 'int', since the
variable used to store the return code 'rc' is an 'int'. This
truncated value is then returned back as a 'ssize_t' back from
perf_stats_show() to 'dev_attr_show()' which thinks of it as a large
unsigned number and triggers this warning..
To fix this we update the type of variable 'rc' from 'int' to
'ssize_t' that prevents the compiler from truncating the return value
of drc_pmem_query_stats() and returning correct signed value back from
Fixes: 2d02bf835e573 ('powerpc/papr_scm: Fetch nvdimm performance
stats from PHYP')
Please don't word wrap the Fixes tag it breaks b4.
I've fixed it up this time.