linux-kernel - [PATCH v0 3/6] perf/x86/intel/pt: Use pointer arithmetics instead in ToPA entry calculation

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Date:   Wed, 21 Aug 2019 15:47:24 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [PATCH v0 3/6] 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>
---
 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 831163a1b41a..15e7c11e3460 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);
-- 
2.23.0.rc1