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SubjectRe: [PATCH 2/5] arm64: perf: Implement correct cap_user_time
Hi Peter,

I love your patch! Yet something to improve:

[auto build test ERROR on tip/perf/core]
[also build test ERROR on arm64/for-next/core arm-perf/for-next/perf linus/master v5.7-rc5 next-20200512]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url: https://github.com/0day-ci/linux/commits/Peter-Zijlstra/arm64-perf-Proper-cap_user_time-support/20200512-205141
base: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git 059c6d68cfc5f85ba3ab71d71a6de380016f7936
config: arm64-allyesconfig (attached as .config)
compiler: aarch64-linux-gcc (GCC) 9.3.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day GCC_VERSION=9.3.0 make.cross ARCH=arm64

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

arch/arm64/kernel/perf_event.c: In function 'arch_perf_update_userpage':
>> arch/arm64/kernel/perf_event.c:1205:12: error: 'struct perf_event_mmap_page' has no member named 'shift'
1205 | if (userpg->shift == 32) {
| ^~
arch/arm64/kernel/perf_event.c:1206:9: error: 'struct perf_event_mmap_page' has no member named 'shift'
1206 | userpg->shift = 31;
| ^~

vim +1205 arch/arm64/kernel/perf_event.c

1165
1166 void arch_perf_update_userpage(struct perf_event *event,
1167 struct perf_event_mmap_page *userpg, u64 now)
1168 {
1169 struct clock_read_data *rd;
1170 unsigned int seq;
1171
1172 /*
1173 * Internal timekeeping for enabled/running/stopped times
1174 * is always computed with the sched_clock.
1175 */
1176 userpg->cap_user_time = 1;
1177 userpg->cap_user_time_zero = 1;
1178
1179 do {
1180 rd = sched_clock_read_begin(&seq);
1181
1182 userpg->time_mult = rd->mult;
1183 userpg->time_shift = rd->shift;
1184 userpg->time_zero = rd->epoch_ns;
1185
1186 /*
1187 * This isn't strictly correct, the ARM64 counter can be
1188 * 'short' and then we get funnies when it wraps. The correct
1189 * thing would be to extend the perf ABI with a cycle and mask
1190 * value, but because wrapping on ARM64 is very rare in
1191 * practise this 'works'.
1192 */
1193 userpg->time_zero -= (rd->epoch_cyc * rd->mult) >> rd->shift;
1194
1195 } while (sched_clock_read_retry(seq));
1196
1197 userpg->time_offset = userpg->time_zero - now;
1198
1199 /*
1200 * time_shift is not expected to be greater than 31 due to
1201 * the original published conversion algorithm shifting a
1202 * 32-bit value (now specifies a 64-bit value) - refer
1203 * perf_event_mmap_page documentation in perf_event.h.
1204 */
> 1205 if (userpg->shift == 32) {
1206 userpg->shift = 31;
1207 userpg->time_mult >>= 1;
1208 }
1209

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
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