linux-kernel - [tip: perf/core] perf/x86/intel/pt: Use pointer arithmetics instead in ToPA entry calculation

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Date:   Mon, 26 Aug 2019 11:45:44 -0000
From:   tip-bot2 for Alexander Shishkin <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Peter Zijlstra <peterz@...radead.org>,
        Stephane Eranian <eranian@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vince Weaver <vincent.weaver@...ne.edu>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org
Subject: [tip: perf/core] perf/x86/intel/pt: Use pointer arithmetics instead
 in ToPA entry calculation

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

Commit-ID:     539f7c26b41d4ed7d88dd9756de3966ae7ca07b4
Gitweb:        https://git.kernel.org/tip/539f7c26b41d4ed7d88dd9756de3966ae7ca07b4
Author:        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
AuthorDate:    Wed, 21 Aug 2019 15:47:24 +03:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Mon, 26 Aug 2019 12:00:13 +02:00

perf/x86/intel/pt: Use pointer arithmetics instead in ToPA entry calculation

Currently, pt_buffer_reset_offsets() calculates the current ToPA entry by
casting pointers to addresses and performing ungainly subtractions and
divisions instead of a simpler pointer arithmetic, which would be perfectly
applicable in that case. Fix that.

Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Vince Weaver <vincent.weaver@...ne.edu>
Link: http://lkml.kernel.org/r/20190821124727.73310-4-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/events/intel/pt.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index f269875..188d45f 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -1030,8 +1030,7 @@ static void pt_buffer_reset_offsets(struct pt_buffer *buf, unsigned long head)
 	pg = pt_topa_next_entry(buf, pg);
 
 	buf->cur = (struct topa *)((unsigned long)buf->topa_index[pg] & PAGE_MASK);
-	buf->cur_idx = ((unsigned long)buf->topa_index[pg] -
-			(unsigned long)buf->cur) / sizeof(struct topa_entry);
+	buf->cur_idx = buf->topa_index[pg] - TOPA_ENTRY(buf->cur, 0);
 	buf->output_off = head & (pt_buffer_region_size(buf) - 1);
 
 	local64_set(&buf->head, head);