perf/x86/intel: Do not enable BTS for guests

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commit 91dcfae0ff upstream.

By default when users program perf to sample branch instructions
(PERF_COUNT_HW_BRANCH_INSTRUCTIONS) with a sample period of 1, perf
interprets this as a special case and enables BTS (Branch Trace Store)
as an optimization to avoid taking an interrupt on every branch.

Since BTS doesn't virtualize, this optimization doesn't make sense when
the request originates from a guest. Add an additional check that
prevents this optimization for virtualized events (exclude_host).

Reported-by: Jan H. Schönherr <jschoenh@amazon.de>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Fernand Sieber <sieberf@amazon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Link: https://patch.msgid.link/20251211183604.868641-1-sieberf@amazon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

This commit is contained in:

Fernand Sieber 2025-12-11 20:36:04 +02:00 • committed by Greg Kroah-Hartman

parent f8cf1368e0

commit cdb3f95a94

1 changed files with 11 additions and 2 deletions

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arch/x86/events/perf_event.h

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