linux-kernel - [tip: perf/urgent] perf/x86/intel/pt: Fix sampling using single range output

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Date:   Wed, 16 Nov 2022 09:21:56 -0000
From:   "tip-bot2 for Adrian Hunter" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        stable@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: perf/urgent] perf/x86/intel/pt: Fix sampling using single range output

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

Commit-ID:     ce0d998be9274dd3a3d971cbeaa6fe28fd2c3062
Gitweb:        https://git.kernel.org/tip/ce0d998be9274dd3a3d971cbeaa6fe28fd2c3062
Author:        Adrian Hunter <adrian.hunter@...el.com>
AuthorDate:    Sat, 12 Nov 2022 17:15:08 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 16 Nov 2022 10:12:59 +01:00

perf/x86/intel/pt: Fix sampling using single range output

Deal with errata TGL052, ADL037 and RPL017 "Trace May Contain Incorrect
Data When Configured With Single Range Output Larger Than 4KB" by
disabling single range output whenever larger than 4KB.

Fixes: 670638477aed ("perf/x86/intel/pt: Opportunistically use single range output mode")
Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: stable@...r.kernel.org
Link: https://lkml.kernel.org/r/20221112151508.13768-1-adrian.hunter@intel.com
---
 arch/x86/events/intel/pt.c |  9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index 82ef87e..42a5579 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -1263,6 +1263,15 @@ static int pt_buffer_try_single(struct pt_buffer *buf, int nr_pages)
 	if (1 << order != nr_pages)
 		goto out;
 
+	/*
+	 * Some processors cannot always support single range for more than
+	 * 4KB - refer errata TGL052, ADL037 and RPL017. Future processors might
+	 * also be affected, so for now rather than trying to keep track of
+	 * which ones, just disable it for all.
+	 */
+	if (nr_pages > 1)
+		goto out;
+
 	buf->single = true;
 	buf->nr_pages = nr_pages;
 	ret = 0;