From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 99274C3A5A1 for ; Sat, 31 Aug 2019 09:06:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7795423697 for ; Sat, 31 Aug 2019 09:06:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727166AbfHaJGV (ORCPT ); Sat, 31 Aug 2019 05:06:21 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:54404 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726116AbfHaJGU (ORCPT ); Sat, 31 Aug 2019 05:06:20 -0400 Received: from [5.158.153.53] (helo=tip-bot2.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1i3zKf-0006D2-RA; Sat, 31 Aug 2019 11:06:05 +0200 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id 713C51C0DCA; Sat, 31 Aug 2019 11:06:05 +0200 (CEST) Date: Sat, 31 Aug 2019 09:06:05 -0000 From: "tip-bot2 for Kim Phillips" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: perf/urgent] perf/x86/amd/ibs: Fix sample bias for dispatched micro-ops Cc: Kim Phillips , "Peter Zijlstra (Intel)" , "Arnaldo Carvalho de Melo" , , Ingo Molnar , Ingo Molnar , Jiri Olsa , Thomas Gleixner , "Borislav Petkov" , Stephane Eranian , Alexander Shishkin , "Namhyung Kim" , "H. Peter Anvin" , linux-kernel@vger.kernel.org In-Reply-To: <20190826195730.30614-1-kim.phillips@amd.com> References: <20190826195730.30614-1-kim.phillips@amd.com> MIME-Version: 1.0 Message-ID: <156724236532.10782.17844013749559561663.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the perf/urgent branch of tip: Commit-ID: 0f4cd769c410e2285a4e9873a684d90423f03090 Gitweb: https://git.kernel.org/tip/0f4cd769c410e2285a4e9873a684d90423f03090 Author: Kim Phillips AuthorDate: Mon, 26 Aug 2019 14:57:30 -05:00 Committer: Peter Zijlstra CommitterDate: Fri, 30 Aug 2019 14:27:47 +02:00 perf/x86/amd/ibs: Fix sample bias for dispatched micro-ops When counting dispatched micro-ops with cnt_ctl=1, in order to prevent sample bias, IBS hardware preloads the least significant 7 bits of current count (IbsOpCurCnt) with random values, such that, after the interrupt is handled and counting resumes, the next sample taken will be slightly perturbed. The current count bitfield is in the IBS execution control h/w register, alongside the maximum count field. Currently, the IBS driver writes that register with the maximum count, leaving zeroes to fill the current count field, thereby overwriting the random bits the hardware preloaded for itself. Fix the driver to actually retain and carry those random bits from the read of the IBS control register, through to its write, instead of overwriting the lower current count bits with zeroes. Tested with: perf record -c 100001 -e ibs_op/cnt_ctl=1/pp -a -C 0 taskset -c 0 'perf annotate' output before: 15.70 65: addsd %xmm0,%xmm1 17.30 add $0x1,%rax 15.88 cmp %rdx,%rax je 82 17.32 72: test $0x1,%al jne 7c 7.52 movapd %xmm1,%xmm0 5.90 jmp 65 8.23 7c: sqrtsd %xmm1,%xmm0 12.15 jmp 65 'perf annotate' output after: 16.63 65: addsd %xmm0,%xmm1 16.82 add $0x1,%rax 16.81 cmp %rdx,%rax je 82 16.69 72: test $0x1,%al jne 7c 8.30 movapd %xmm1,%xmm0 8.13 jmp 65 8.24 7c: sqrtsd %xmm1,%xmm0 8.39 jmp 65 Tested on Family 15h and 17h machines. Machines prior to family 10h Rev. C don't have the RDWROPCNT capability, and have the IbsOpCurCnt bitfield reserved, so this patch shouldn't affect their operation. It is unknown why commit db98c5faf8cb ("perf/x86: Implement 64-bit counter support for IBS") ignored the lower 4 bits of the IbsOpCurCnt field; the number of preloaded random bits has always been 7, AFAICT. Signed-off-by: Kim Phillips Signed-off-by: Peter Zijlstra (Intel) Cc: "Arnaldo Carvalho de Melo" Cc: Cc: Ingo Molnar Cc: Ingo Molnar Cc: Jiri Olsa Cc: Thomas Gleixner Cc: "Borislav Petkov" Cc: Stephane Eranian Cc: Alexander Shishkin Cc: "Namhyung Kim" Cc: "H. Peter Anvin" Link: https://lkml.kernel.org/r/20190826195730.30614-1-kim.phillips@amd.com --- arch/x86/events/amd/ibs.c | 13 ++++++++++--- arch/x86/include/asm/perf_event.h | 12 ++++++++---- 2 files changed, 18 insertions(+), 7 deletions(-) diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c index 62f317c..5b35b7e 100644 --- a/arch/x86/events/amd/ibs.c +++ b/arch/x86/events/amd/ibs.c @@ -661,10 +661,17 @@ static int perf_ibs_handle_irq(struct perf_ibs *perf_ibs, struct pt_regs *iregs) throttle = perf_event_overflow(event, &data, ®s); out: - if (throttle) + if (throttle) { perf_ibs_stop(event, 0); - else - perf_ibs_enable_event(perf_ibs, hwc, period >> 4); + } else { + period >>= 4; + + if ((ibs_caps & IBS_CAPS_RDWROPCNT) && + (*config & IBS_OP_CNT_CTL)) + period |= *config & IBS_OP_CUR_CNT_RAND; + + perf_ibs_enable_event(perf_ibs, hwc, period); + } perf_event_update_userpage(event); diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h index 1392d5e..ee26e92 100644 --- a/arch/x86/include/asm/perf_event.h +++ b/arch/x86/include/asm/perf_event.h @@ -252,16 +252,20 @@ struct pebs_lbr { #define IBSCTL_LVT_OFFSET_VALID (1ULL<<8) #define IBSCTL_LVT_OFFSET_MASK 0x0F -/* ibs fetch bits/masks */ +/* IBS fetch bits/masks */ #define IBS_FETCH_RAND_EN (1ULL<<57) #define IBS_FETCH_VAL (1ULL<<49) #define IBS_FETCH_ENABLE (1ULL<<48) #define IBS_FETCH_CNT 0xFFFF0000ULL #define IBS_FETCH_MAX_CNT 0x0000FFFFULL -/* ibs op bits/masks */ -/* lower 4 bits of the current count are ignored: */ -#define IBS_OP_CUR_CNT (0xFFFF0ULL<<32) +/* + * IBS op bits/masks + * The lower 7 bits of the current count are random bits + * preloaded by hardware and ignored in software + */ +#define IBS_OP_CUR_CNT (0xFFF80ULL<<32) +#define IBS_OP_CUR_CNT_RAND (0x0007FULL<<32) #define IBS_OP_CNT_CTL (1ULL<<19) #define IBS_OP_VAL (1ULL<<18) #define IBS_OP_ENABLE (1ULL<<17)