H_GetPerformanceCounterInfo (0xF080) hcall returns the counter data in the result buffer. Result buffer has specific format defined in the PAPR specification. One of the field is counter offset and width of the counter data returned.
Counter data are returned in a unsigned char array. To get the final counter data, these values should be left shifted byte at a time. But commit 220a0c609ad17 ("powerpc/perf: Add support for the hv gpci (get performance counter info) interface") made the shifting bitwise. Because of this, hcall counters values could end up in lower side, which messes the counter prev vs now calculation. This lead to huge counter value reporting [command]#: perf stat -e hv_gpci/system_tlbie_count_and_time_tlbie_instructions_issued/ -C 0 -I 1000 time counts unit events 1.000078854 18,446,744,073,709,535,232 hv_gpci/system_tlbie_count_and_time_tlbie_instructions_issued/ 2.000213293 0 hv_gpci/system_tlbie_count_and_time_tlbie_instructions_issued/ 3.000320107 0 hv_gpci/system_tlbie_count_and_time_tlbie_instructions_issued/ 4.000428392 0 hv_gpci/system_tlbie_count_and_time_tlbie_instructions_issued/ 5.000537864 0 hv_gpci/system_tlbie_count_and_time_tlbie_instructions_issued/ 6.000649087 0 hv_gpci/system_tlbie_count_and_time_tlbie_instructions_issued/ 7.000760312 0 hv_gpci/system_tlbie_count_and_time_tlbie_instructions_issued/ 8.000865218 16,448 hv_gpci/system_tlbie_count_and_time_tlbie_instructions_issued/ 9.000978985 18,446,744,073,709,535,232 hv_gpci/system_tlbie_count_and_time_tlbie_instructions_issued/ 10.001088891 16,384 hv_gpci/system_tlbie_count_and_time_tlbie_instructions_issued/ 11.001201435 0 hv_gpci/system_tlbie_count_and_time_tlbie_instructions_issued/ 12.001307937 18,446,744,073,709,535,232 hv_gpci/system_tlbie_count_and_time_tlbie_instructions_issued/ Patch here fixes the shifting logic to make is byte-wise with which no more the issue seen. Fixes: e4f226b1580b3 ("powerpc/perf/hv-gpci: Increase request buffer size") Reported-by: Nageswara R Sastry<rnsas...@linux.ibm.com> Signed-off-by: Kajol Jain <kj...@linux.ibm.com> --- arch/powerpc/perf/hv-gpci.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/perf/hv-gpci.c b/arch/powerpc/perf/hv-gpci.c index d48413e28c39..c756228a081f 100644 --- a/arch/powerpc/perf/hv-gpci.c +++ b/arch/powerpc/perf/hv-gpci.c @@ -175,7 +175,7 @@ static unsigned long single_gpci_request(u32 req, u32 starting_index, */ count = 0; for (i = offset; i < offset + length; i++) - count |= arg->bytes[i] << (i - offset); + count |= (u64)(arg->bytes[i]) << ((length - 1 - (i - offset)) * 8); *value = count; out: -- 2.26.2