linux-kernel - [PATCH 1/2] perf/x86/amd/ibs: Fix reading of the IBS OpData register and thus precise RIP validity

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Message-ID: <20191023150955.30292-1-kim.phillips@amd.com>
Date:   Wed, 23 Oct 2019 10:09:54 -0500
From:   Kim Phillips <kim.phillips@....com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        <kim.phillips@....com>
CC:     <stable@...r.kernel.org>, Stephane Eranian <eranian@...gle.com>,
        "Arnaldo Carvalho de Melo" <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        "Namhyung Kim" <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Borislav Petkov" <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
        <x86@...nel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/2] perf/x86/amd/ibs: Fix reading of the IBS OpData register and thus precise RIP validity

The loop that reads all the IBS MSRs into *buf stopped one MSR short of
reading the IbsOpData register, which contains the RipInvalid status bit.

Fix the offset_max assignment so the MSR gets read, so the RIP invalid
evaluation is based on what the IBS h/w output, instead of what was
left in memory.

Signed-off-by: Kim Phillips <kim.phillips@....com>
Fixes: d47e8238cd76 ("perf/x86-ibs: Take instruction pointer from ibs sample")
Cc: stable@...r.kernel.org
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Borislav Petkov <bp@...en8.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: x86@...nel.org
Cc: linux-kernel@...r.kernel.org
---
 arch/x86/events/amd/ibs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
index 5b35b7ea5d72..98ba21a588a1 100644
--- a/arch/x86/events/amd/ibs.c
+++ b/arch/x86/events/amd/ibs.c
@@ -614,7 +614,7 @@ static int perf_ibs_handle_irq(struct perf_ibs *perf_ibs, struct pt_regs *iregs)
 	if (event->attr.sample_type & PERF_SAMPLE_RAW)
 		offset_max = perf_ibs->offset_max;
 	else if (check_rip)
-		offset_max = 2;
+		offset_max = 3;
 	else
 		offset_max = 1;
 	do {
-- 
2.23.0