Re: [PATCH] powerpc/perf/hv-gpci: Fix the logic to compute counter value from the hcall result buffer.

On Fri, 13 Aug 2021 13:51:58 +0530, Kajol Jain wrote:

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

[...]

Applied to powerpc/next.

[1/1] powerpc/perf/hv-gpci: Fix the logic to compute counter value from the hcall result buffer.
      https://git.kernel.org/powerpc/c/f9addd85fbfacf0d155e83dbee8696d6df5ed0c7

cheers