Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
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: c1961a4 ("x86/events/intel/ds: Map debug buffers in cpu_entry_area") Reported-and-tested-by: Markus T Metzger <[email protected]> Signed-off-by: Hugh Dickins <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: Alexander Shishkin <[email protected]> Cc: Andi Kleen <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Stephane Eranian <[email protected]> Cc: [email protected] # v4.14+ Link: https://lkml.kernel.org/r/[email protected]
- Loading branch information