From: Kajol Jain kjain@linux.ibm.com
commit f9addd85fbfacf0d155e83dbee8696d6df5ed0c7 upstream.
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 fields is counter offset and width of the counter data returned.
Counter data are returned in a unsigned char array in big endian byte order. To get the final counter data, the values must 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 and also assumed little endian order. Because of that, hcall counters values are reported incorrectly.
In particular this can lead to counters go backwards which messes up the counter prev vs now calculation and leads to huge counter value reporting:
#: 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/
Fix the shifting logic to correct match the format, ie. read bytes in big endian order.
Fixes: e4f226b1580b ("powerpc/perf/hv-gpci: Increase request buffer size") Cc: stable@vger.kernel.org # v4.6+ Reported-by: Nageswara R Sastryrnsastry@linux.ibm.com Signed-off-by: Kajol Jain kjain@linux.ibm.com Tested-by: Nageswara R Sastryrnsastry@linux.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20210813082158.429023-1-kjain@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/perf/hv-gpci.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/powerpc/perf/hv-gpci.c +++ b/arch/powerpc/perf/hv-gpci.c @@ -164,7 +164,7 @@ static unsigned long single_gpci_request */ 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: