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| author | Hugh Dickins <hughd@google.com> | 2018-07-14 21:58:07 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2018-07-15 11:38:44 +0200 |
| commit | 2c991e408df6a407476dbc453d725e1e975479e7 (patch) | |
| tree | 6ae5f018abe25b8cfa3b66e6c83cb8b5e5355066 /arch | |
| parent | Merge tag 'rtc-4.18-2' of git://git.kernel.org/pub/scm/linux/kernel/git/abell... (diff) | |
| download | linux-2c991e408df6a407476dbc453d725e1e975479e7.tar.xz linux-2c991e408df6a407476dbc453d725e1e975479e7.zip | |
x86/events/intel/ds: Fix bts_interrupt_threshold alignment
Markus reported that BTS is sporadically missing the tail of the trace
in the perf_event data buffer: [decode error (1): instruction overflow]
shown in GDB; and bisected it to the conversion of debug_store to PTI.
A little "optimization" crept into alloc_bts_buffer(), which mistakenly
placed bts_interrupt_threshold away from the 24-byte record boundary.
Intel SDM Vol 3B 17.4.9 says "This address must point to an offset from
the BTS buffer base that is a multiple of the BTS record size."
Revert "max" from a byte count to a record count, to calculate the
bts_interrupt_threshold correctly: which turns out to fix problem seen.
Fixes: c1961a4631da ("x86/events/intel/ds: Map debug buffers in cpu_entry_area")
Reported-and-tested-by: Markus T Metzger <markus.t.metzger@intel.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@intel.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: stable@vger.kernel.org # v4.14+
Link: https://lkml.kernel.org/r/alpine.LSU.2.11.1807141248290.1614@eggly.anvils
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/events/intel/ds.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c index 8a10a045b57b..8cf03f101938 100644 --- a/arch/x86/events/intel/ds.c +++ b/arch/x86/events/intel/ds.c @@ -408,9 +408,11 @@ static int alloc_bts_buffer(int cpu) ds->bts_buffer_base = (unsigned long) cea; ds_update_cea(cea, buffer, BTS_BUFFER_SIZE, PAGE_KERNEL); ds->bts_index = ds->bts_buffer_base; - max = BTS_RECORD_SIZE * (BTS_BUFFER_SIZE / BTS_RECORD_SIZE); - ds->bts_absolute_maximum = ds->bts_buffer_base + max; - ds->bts_interrupt_threshold = ds->bts_absolute_maximum - (max / 16); + max = BTS_BUFFER_SIZE / BTS_RECORD_SIZE; + ds->bts_absolute_maximum = ds->bts_buffer_base + + max * BTS_RECORD_SIZE; + ds->bts_interrupt_threshold = ds->bts_absolute_maximum - + (max / 16) * BTS_RECORD_SIZE; return 0; } |