On platforms with large number of Pstates, the transition table, which
is a NxN matrix, can overflow beyond the PAGE_SIZE boundary.
This can be seen on POWER9 which has 100+ Pstates.
As a result, each time the trans_table is read for any of the CPUs, we
will get the following error.
---------------------------------------------------
fill_read_buffer: show+0x0/0xa0 returned bad count
---------------------------------------------------
This patch ensures that in case of an overflow, we print a warning
once in the dmesg and return FILE TOO LARGE error for this and all
subsequent accesses of trans_table.
Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Freq_j is in descending order with increasing columns. The output here also
contains the actual freq values for each row and column for better readability.
+If the transition table is bigger than PAGE_SIZE, reading this will
+return an -EFBIG error.
+
--------------------------------------------------------------------------------
<mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat trans_table
From : To
break;
len += snprintf(buf + len, PAGE_SIZE - len, "\n");
}
- if (len >= PAGE_SIZE)
- return PAGE_SIZE;
+
+ if (len >= PAGE_SIZE) {
+ pr_warn_once("cpufreq transition table exceeds PAGE_SIZE. Disabling\n");
+ return -EFBIG;
+ }
return len;
}
cpufreq_freq_attr_ro(trans_table);