linux-kernel - [tip: perf/core] perf/x86/amd: Don't reject non-sampling events with configured LBR

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Message-ID: <171213002604.10875.4290828436978142700.tip-bot2@tip-bot2>
Date: Wed, 03 Apr 2024 07:40:26 -0000
From: "tip-bot2 for Andrii Nakryiko" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Andrii Nakryiko <andrii@...nel.org>, Ingo Molnar <mingo@...nel.org>,
 Sandipan Das <sandipan.das@....com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: perf/core] perf/x86/amd: Don't reject non-sampling events with
 configured LBR

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     9794563d4d053b1b46a0cc91901f0a11d8678c19
Gitweb:        https://git.kernel.org/tip/9794563d4d053b1b46a0cc91901f0a11d8678c19
Author:        Andrii Nakryiko <andrii@...nel.org>
AuthorDate:    Mon, 01 Apr 2024 19:21:18 -07:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Wed, 03 Apr 2024 09:14:26 +02:00

perf/x86/amd: Don't reject non-sampling events with configured LBR

Now that it's possible to capture LBR on AMD CPU from BPF at arbitrary
point, there is no reason to artificially limit this feature to just
sampling events. So corresponding check is removed. AFAIU, there is no
correctness implications of doing this (and it was possible to bypass
this check by just setting perf_event's sample_period to 1 anyways, so
it doesn't guard all that much).

Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Sandipan Das <sandipan.das@....com>
Link: https://lore.kernel.org/r/20240402022118.1046049-5-andrii@kernel.org
---
 arch/x86/events/amd/lbr.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/x86/events/amd/lbr.c b/arch/x86/events/amd/lbr.c
index 33d0a45..19c7b76 100644
--- a/arch/x86/events/amd/lbr.c
+++ b/arch/x86/events/amd/lbr.c
@@ -310,10 +310,6 @@ int amd_pmu_lbr_hw_config(struct perf_event *event)
 {
 	int ret = 0;
 
-	/* LBR is not recommended in counting mode */
-	if (!is_sampling_event(event))
-		return -EINVAL;
-
 	ret = amd_pmu_lbr_setup_filter(event);
 	if (!ret)
 		event->attach_state |= PERF_ATTACH_SCHED_CB;