3.16.80-rc1 review patch. If anyone has any objections, please let me know.
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From: Alexey Brodkin Alexey.Brodkin@synopsys.com
commit 5effc09c4907901f0e71e68e5f2e14211d9a203f upstream.
8-letter strings representing ARC perf events are stores in two 32-bit registers as ASCII characters like that: "IJMP", "IALL", "IJMPTAK" etc.
And the same order of bytes in the word is used regardless CPU endianness.
Which means in case of big-endian CPU core we need to swap bytes to get the same order as if it was on little-endian CPU.
Otherwise we're seeing the following error message on boot: ------------------------->8---------------------- ARC perf : 8 counters (32 bits), 40 conditions, [overflow IRQ support] sysfs: cannot create duplicate filename '/devices/arc_pct/events/pmji' CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.2.18 #3 Stack Trace: arc_unwind_core+0xd4/0xfc dump_stack+0x64/0x80 sysfs_warn_dup+0x46/0x58 sysfs_add_file_mode_ns+0xb2/0x168 create_files+0x70/0x2a0 ------------[ cut here ]------------ WARNING: CPU: 0 PID: 1 at kernel/events/core.c:12144 perf_event_sysfs_init+0x70/0xa0 Failed to register pmu: arc_pct, reason -17 Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.2.18 #3 Stack Trace: arc_unwind_core+0xd4/0xfc dump_stack+0x64/0x80 __warn+0x9c/0xd4 warn_slowpath_fmt+0x22/0x2c perf_event_sysfs_init+0x70/0xa0 ---[ end trace a75fb9a9837bd1ec ]--- ------------------------->8----------------------
What happens here we're trying to register more than one raw perf event with the same name "PMJI". Why? Because ARC perf events are 4 to 8 letters and encoded into two 32-bit words. In this particular case we deal with 2 events: * "IJMP____" which counts all jump & branch instructions * "IJMPC___" which counts only conditional jumps & branches
Those strings are split in two 32-bit words this way "IJMP" + "____" & "IJMP" + "C___" correspondingly. Now if we read them swapped due to CPU core being big-endian then we read "PMJI" + "____" & "PMJI" + "___C".
And since we interpret read array of ASCII letters as a null-terminated string on big-endian CPU we end up with 2 events of the same name "PMJI".
Signed-off-by: Alexey Brodkin abrodkin@synopsys.com Signed-off-by: Vineet Gupta vgupta@synopsys.com [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- arch/arc/kernel/perf_event.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/arc/kernel/perf_event.c +++ b/arch/arc/kernel/perf_event.c @@ -274,8 +274,8 @@ static int arc_pmu_device_probe(struct p
for (j = 0; j < cc_bcr.c; j++) { write_aux_reg(ARC_REG_CC_INDEX, j); - cc_name.indiv.word0 = read_aux_reg(ARC_REG_CC_NAME0); - cc_name.indiv.word1 = read_aux_reg(ARC_REG_CC_NAME1); + cc_name.indiv.word0 = le32_to_cpu(read_aux_reg(ARC_REG_CC_NAME0)); + cc_name.indiv.word1 = le32_to_cpu(read_aux_reg(ARC_REG_CC_NAME1)); for (i = 0; i < ARRAY_SIZE(arc_pmu_ev_hw_map); i++) { if (arc_pmu_ev_hw_map[i] && !strcmp(arc_pmu_ev_hw_map[i], cc_name.str) &&