[PATCH 0/2] perf: Fix AUX software double buffering

From: Alexander Shishkin
Date: Fri May 03 2019 - 04:56:10 EST

Hi Peter,

There was a problem with 04fe30a61514 ("perf/ring_buffer: Use high order
allocations for AUX buffers optimistically") that made buffers that were
previously scattered across multiple pages into one large buffer, breaking
double buffering. In practice, this manifests easily for non-privileged
users, whose buffers are generally smaller than MAX_ORDER and would fit
into one high-order allocation. Root's default AUX buffer size is larger
and would get split, so they are less affected. The fix is trivial and
we also get rid of one PMU capability as a bonus.

Alexander Shishkin (2):
perf: Fix AUX software double buffering
perf, pt: Remove software double buffering PMU capability

arch/x86/events/intel/pt.c | 3 +--
include/linux/perf_event.h | 1 -
kernel/events/ring_buffer.c | 3 +--
3 files changed, 2 insertions(+), 5 deletions(-)