From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755244Ab1CUX52 (ORCPT ); Mon, 21 Mar 2011 19:57:28 -0400 Received: from kroah.org ([198.145.64.141]:49090 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755029Ab1CUXOB (ORCPT ); Mon, 21 Mar 2011 19:14:01 -0400 X-Mailbox-Line: From gregkh@clark.kroah.org Mon Mar 21 16:10:53 2011 Message-Id: <20110321231053.754570720@clark.kroah.org> User-Agent: quilt/0.48-16.4 Date: Mon, 21 Mar 2011 16:10:10 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Anton Blanchard , Peter Zijlstra , Ingo Molnar Subject: [30/44] perf, powerpc: Handle events that raise an exception without overflowing In-Reply-To: <20110321231105.GA1744@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-longterm review patch. If anyone has any objections, please let us know. ------------------ From: Anton Blanchard commit 0837e3242c73566fc1c0196b4ec61779c25ffc93 upstream. Events on POWER7 can roll back if a speculative event doesn't eventually complete. Unfortunately in some rare cases they will raise a performance monitor exception. We need to catch this to ensure we reset the PMC. In all cases the PMC will be 256 or less cycles from overflow. Signed-off-by: Anton Blanchard Signed-off-by: Peter Zijlstra LKML-Reference: <20110309143842.6c22845e@kryten> Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/include/asm/reg.h | 1 + arch/powerpc/kernel/perf_event.c | 24 +++++++++++++++++++++++- 2 files changed, 24 insertions(+), 1 deletion(-) --- a/arch/powerpc/include/asm/reg.h +++ b/arch/powerpc/include/asm/reg.h @@ -858,6 +858,7 @@ #define PV_970 0x0039 #define PV_POWER5 0x003A #define PV_POWER5p 0x003B +#define PV_POWER7 0x003F #define PV_970FX 0x003C #define PV_630 0x0040 #define PV_630p 0x0041 --- a/arch/powerpc/kernel/perf_event.c +++ b/arch/powerpc/kernel/perf_event.c @@ -1220,6 +1220,28 @@ unsigned long perf_instruction_pointer(s return ip; } +static bool pmc_overflow(unsigned long val) +{ + if ((int)val < 0) + return true; + + /* + * Events on POWER7 can roll back if a speculative event doesn't + * eventually complete. Unfortunately in some rare cases they will + * raise a performance monitor exception. We need to catch this to + * ensure we reset the PMC. In all cases the PMC will be 256 or less + * cycles from overflow. + * + * We only do this if the first pass fails to find any overflowing + * PMCs because a user might set a period of less than 256 and we + * don't want to mistakenly reset them. + */ + if (__is_processor(PV_POWER7) && ((0x80000000 - val) <= 256)) + return true; + + return false; +} + /* * Performance monitor interrupt stuff */ @@ -1267,7 +1289,7 @@ static void perf_event_interrupt(struct if (is_limited_pmc(i + 1)) continue; val = read_pmc(i + 1); - if ((int)val < 0) + if (pmc_overflow(val)) write_pmc(i + 1, 0); } }