From d79cb9f57f5713c100e6ff1b6e94292ebbc41b2d Mon Sep 17 00:00:00 2001

From: Kajol Jain <kjain@linux.ibm.com>

Date: Fri, 13 Aug 2021 13:51:58 +0530

Subject: [PATCH] powerpc/perf/hv-gpci: Fix counter value parsing

Git-commit: f9addd85fbfacf0d155e83dbee8696d6df5ed0c7

Patch-mainline: v5.15-rc1

References: stable-5.14.6

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 Sastry<rnsastry@linux.ibm.com>

Signed-off-by: Kajol Jain <kjain@linux.ibm.com>

Tested-by: Nageswara R Sastry<rnsastry@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>

Acked-by: Takashi Iwai <tiwai@suse.de>

---

 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