[PATCH] perf/x86/intel: Don't accidentally clear high bits in bdw_limit_period()

[PATCH] perf/x86/intel: Don't accidentally clear high bits in bdw_limit_period()

[Dan Carpenter]

We intended to clear the lowest 6 bits but because of a type bug we
clear the high 32 bits as well.  Andi says that periods are rarely more
than U32_MAX so this bug probably doesn't have a huge runtime impact.

Fixes: 294fe0f52a44 ("perf/x86/intel: Add INST_RETIRED.ALL workarounds")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 41c68d337e84..f23f52b9de8e 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3210,7 +3210,7 @@ static u64 bdw_limit_period(struct perf_event *event, u64 left)
 			X86_CONFIG(.event=0xc0, .umask=0x01)) {
 		if (left < 128)
 			left = 128;
-		left &= ~0x3fu;
+		left &= ~0x3fULL;
 	}
 	return left;
 }

Re: [PATCH] perf/x86/intel: Don't accidentally clear high bits in bdw_limit_period()

[Peter Zijlstra]

On Sat, Mar 17, 2018 at 02:52:16PM +0300, Dan Carpenter wrote:
> We intended to clear the lowest 6 bits but because of a type bug we
> clear the high 32 bits as well.  Andi says that periods are rarely more
> than U32_MAX so this bug probably doesn't have a huge runtime impact.

Thanks Dan!

[tip:perf/urgent] perf/x86/intel: Don't accidentally clear high bits in bdw_limit_period()

[tip-bot for Dan Carpenter]

Commit-ID:  e5ea9b54a055619160bbfe527ebb7d7191823d66
Gitweb:     https://git.kernel.org/tip/e5ea9b54a055619160bbfe527ebb7d7191823d66
Author:     Dan Carpenter <dan.carpenter@oracle.com>
AuthorDate: Sat, 17 Mar 2018 14:52:16 +0300
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 20 Mar 2018 08:53:31 +0100

perf/x86/intel: Don't accidentally clear high bits in bdw_limit_period()

We intended to clear the lowest 6 bits but because of a type bug we
clear the high 32 bits as well.  Andi says that periods are rarely more
than U32_MAX so this bug probably doesn't have a huge runtime impact.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Fixes: 294fe0f52a44 ("perf/x86/intel: Add INST_RETIRED.ALL workarounds")
Link: http://lkml.kernel.org/r/20180317115216.GB4035@mwanda
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/events/intel/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 56457cb73448..9b18a227fff7 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3194,7 +3194,7 @@ static unsigned bdw_limit_period(struct perf_event *event, unsigned left)
 			X86_CONFIG(.event=0xc0, .umask=0x01)) {
 		if (left < 128)
 			left = 128;
-		left &= ~0x3fu;
+		left &= ~0x3fULL;
 	}
 	return left;
 }