Received: by 2002:a05:6a10:1d13:0:0:0:0 with SMTP id pp19csp48995pxb; Tue, 31 Aug 2021 14:51:49 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzj/9JNUXPAglFQ+SeZ2CkqMWcI91jFfMLyhaEBC4SuXQvvUWZ0XwFIsTYmU9xjqF+phkK6 X-Received: by 2002:aa7:cfd2:: with SMTP id r18mr28766333edy.82.1630446709421; Tue, 31 Aug 2021 14:51:49 -0700 (PDT) ARC-Seal: i=2; a=rsa-sha256; t=1630446709; cv=pass; d=google.com; s=arc-20160816; b=FnWhVj3X16UgjeyDtO9IT1n2h+Fpd26zUIoqtsWe8h3js85izoYJPaYBVYtvSaMcNb ODk3XWbh6UaqwNJySw75ZCsN1lq3f2+GZ6ejakoXCl4xR9qppIQiYXMVYmrPuH6QGanR jo49KdZic12d36UbtXZbp5W8MT9ZrA3MdUimM/lFmgLHBz8j2gc3f/kUaeM904kHD1R7 zz4qjS17i5sIv6rjmBwjdvD3LWRZdoPP9kXMxqUvbLo5SZW8bGpVhxtBPbiGfvc/t33A Wx1MzfxgSMdLUJg8FGK7WnzyP3WnZDsY6zv1ixvRMQ7r8j7iXxJfoT9EaqNhudO4+VdI o0LA== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:mime-version:content-id:content-language :accept-language:in-reply-to:references:message-id:date:thread-index :thread-topic:subject:cc:to:from:dkim-signature; bh=NgjYfCUPlZ4aafdewourUXA8RpBMKOh0FmMZ8LSKhjM=; b=Rtclba+cbAE7KCtsjFJMA34aGxUqyb0nzJX53fozjXHIikSMdmOh3WRxosJDyvuw+d iHcwn5zY+zSlgGBvmwQeD4mEjiddqrTnKIr2TC+NsMVkHRL1r5N9ALncuDwgykNDn655 45+A5UpC7vO2cohlKFmpkEgTf4zC4e6+F7YRy5x9HeOAf6fCq3UjEtgEKxgARX9eJ2Oi 7+AcpJmmPU5+qTrkMaI/lhcMgSzrQ9inedReKZNupylGFEa8qAkWiaO8Tshiy7cSwX36 KHP5JMFpdCJAzsevAaiEVDroP4rygKJXfGgTCLn9UP+5atkkSSjSJ05RM/m73n9ScHVZ TfUA== ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@fb.com header.s=facebook header.b=SG8F0pNc; arc=pass (i=1 spf=pass spfdomain=fb.com dkim=pass dkdomain=fb.com dmarc=pass fromdomain=fb.com); spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=fb.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id nb38si388973ejc.86.2021.08.31.14.51.17; Tue, 31 Aug 2021 14:51:49 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@fb.com header.s=facebook header.b=SG8F0pNc; arc=pass (i=1 spf=pass spfdomain=fb.com dkim=pass dkdomain=fb.com dmarc=pass fromdomain=fb.com); spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=fb.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240305AbhHaVZp (ORCPT + 99 others); Tue, 31 Aug 2021 17:25:45 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:20366 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239889AbhHaVZo (ORCPT ); Tue, 31 Aug 2021 17:25:44 -0400 Received: from pps.filterd (m0109331.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 17VLOYki010958; Tue, 31 Aug 2021 14:24:48 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : references : in-reply-to : content-type : content-id : mime-version; s=facebook; bh=NgjYfCUPlZ4aafdewourUXA8RpBMKOh0FmMZ8LSKhjM=; b=SG8F0pNcNp+s4on/lM8wyet/EKLAh8QpdV6Iu9vXXOuDs+CaNZYvMgz73Peslq5WmIUA Iq/KRdwe2tTnDrJsWT/12NeCLOpI6/qvvxgDkXOQKysVQpQXI7SuRINK/gbSSvj+F7LC cN72IlYqLRLv+LeP2JwXLEprsuMNXR/ertw= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 3asscrsfqh-2 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT); Tue, 31 Aug 2021 14:24:48 -0700 Received: from NAM11-BN8-obe.outbound.protection.outlook.com (100.104.31.183) by o365-in.thefacebook.com (100.104.36.103) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.14; Tue, 31 Aug 2021 14:24:47 -0700 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=la29c71PEWg60C+XsbVkcGwyF0Fh6PBuSwcC8tyUg+nRVx/74gqRVbkQNRe4WJJg0Vv+HIWhQgJ2vSMgROphULEFm+zmNSMg+1bCArnJtiI+OYF42dzPdxq5tFERltllZKzxke0RL88syTPZTa9zv+HVnoKuuWuM9yASfwtPLjtedkpFfzhR7zp+MWFsQrDE/nr3cy5VuVSQQC0gJsj+4aTcbLOxYI+gUXllKqPbYEjV35hsvo0enKkaMJ0m1qimQaXQUVLmIvuzdhtZ5zKPRozacRcJ/DelqwC2QBi/sTGBGhXStwm0g3+AEx9ziN00tEdWo6IMk8IJAkJWcFh+Dw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=NgjYfCUPlZ4aafdewourUXA8RpBMKOh0FmMZ8LSKhjM=; b=FZOpnRaGLYMSmvo0v3wIXcI49P/eMipkNSoPyzaWvHsAckQAVnz11OhZ98z15tmpJ01uP3hincGcRCqRMIUKxSzN07Z2a83HDfCY4lFEq9bqqfpxClUKCwdOhzhGwyGzUSq+ygtQA0qjMDREC90eLSb3URgJqbCDk41j3IFkZ38JhgkI3PmJm2+M6RydCsEdc/ykvDkqbBSQUGPydAcSZPS+VEjIemcmE661yGsflY2tadqiaUNCaVACJoP3qju/bMJ0itl7t+da34ZoHHSGmQ8iGi78HXCBkEY/0J+u4j3rj2vbEYrZ0sV1BsOTYXz7jxvr/smPqlv8kK886E6plQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=fb.com; dmarc=pass action=none header.from=fb.com; dkim=pass header.d=fb.com; arc=none Received: from SA1PR15MB5109.namprd15.prod.outlook.com (2603:10b6:806:1dc::10) by SA1PR15MB5096.namprd15.prod.outlook.com (2603:10b6:806:1df::10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4478.17; Tue, 31 Aug 2021 21:24:46 +0000 Received: from SA1PR15MB5109.namprd15.prod.outlook.com ([fe80::7d66:9b36:b482:af0f]) by SA1PR15MB5109.namprd15.prod.outlook.com ([fe80::7d66:9b36:b482:af0f%7]) with mapi id 15.20.4478.017; Tue, 31 Aug 2021 21:24:46 +0000 From: Song Liu To: Peter Zijlstra CC: "open list:BPF (Safe dynamic programs and tools)" , LKML , Arnaldo Carvalho de Melo , Ingo Molnar , kajoljain , Kernel Team Subject: Re: [PATCH v3 bpf-next 2/3] bpf: introduce helper bpf_get_branch_snapshot Thread-Topic: [PATCH v3 bpf-next 2/3] bpf: introduce helper bpf_get_branch_snapshot Thread-Index: AQHXnefQHoOSP4aCd0m/09RPZ9UWQauNvuuAgAATPICAAE9GgA== Date: Tue, 31 Aug 2021 21:24:46 +0000 Message-ID: References: <20210830214106.4142056-1-songliubraving@fb.com> <20210830214106.4142056-3-songliubraving@fb.com> <26B5B18A-EC0B-4661-BE6F-E5D96DCDE0B9@fb.com> In-Reply-To: <26B5B18A-EC0B-4661-BE6F-E5D96DCDE0B9@fb.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3654.120.0.1.13) authentication-results: infradead.org; dkim=none (message not signed) header.d=none;infradead.org; dmarc=none action=none header.from=fb.com; x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 05b08b0c-c557-4239-a16e-08d96cc5c1bd x-ms-traffictypediagnostic: SA1PR15MB5096: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-fb-source: Internal x-ms-oob-tlc-oobclassifiers: OLM:9508; x-ms-exchange-senderadcheck: 1 x-ms-exchange-antispam-relay: 0 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: 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 x-forefront-antispam-report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:SA1PR15MB5109.namprd15.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(39860400002)(136003)(396003)(366004)(346002)(376002)(54906003)(478600001)(5660300002)(6512007)(316002)(71200400001)(33656002)(86362001)(6486002)(4326008)(38070700005)(6506007)(66946007)(122000001)(83380400001)(64756008)(66446008)(66556008)(76116006)(91956017)(66476007)(186003)(6916009)(2616005)(8676002)(36756003)(8936002)(2906002)(38100700002)(53546011)(45980500001);DIR:OUT;SFP:1102; x-ms-exchange-antispam-messagedata-chunkcount: 1 x-ms-exchange-antispam-messagedata-0: =?us-ascii?Q?/UzjdUQ7B2W7O8GaaEX1IFS4E4VDLud6kgZNXakqFYkLvZ64x4zdOVQkCrY2?= =?us-ascii?Q?EmCK+yI1+RVFXWzAIXf/0y3N5x31wPMmOVPrhmZdnr4N82gs8xBzAd+oI4aH?= =?us-ascii?Q?MfIEDQXIL8vFQAQKw8+sU49Mmt5QPfAbNkDWiHNAuAnNUVv3DPyWzZ/jVBUx?= =?us-ascii?Q?Mp0s/m+im23UvZKpmadFqKnPWI6aPNMAkkqUgoKcMQc6py5rJI3pvBnT/oL1?= =?us-ascii?Q?E+a5ibz/XijGBY4hi8i1eKwHfE07gPiGNg3jX8MSyWC5oE2xB9a8JzCBJmzm?= =?us-ascii?Q?5VxBv69gp+F0n4i365fTFnOW6cE86maCQf1y5tQA0VUtM4XVm+uX1Upkk8Cq?= =?us-ascii?Q?wFtAGBnOX62x2gwJiBFYx9kDczNfjjxH4KsH3FRELryKBECZYD/mtIdAsV1S?= =?us-ascii?Q?kVZZDnNyIXPBP9OER91zKKch3Y03x3rCX0OU4l1IIMBuY+F4CUAfFE5wpSpd?= =?us-ascii?Q?sQ4+IQuRf5jybqNEgGKXZw7wOOg7DHv+RGp4+KRyxcY5T7F0RydUBeIYGeBn?= =?us-ascii?Q?342Ng5j0El9IFf6kIW7mZAFn3xMAhce43K0j89JtS1Dpwbpb5lxNu/J1VC7L?= =?us-ascii?Q?Ue1sEbLCviSsAMUQ+YnmlP+GIY8BkGAnpXQk1f/YCfRDAG1zV3PkbulL/BHj?= =?us-ascii?Q?Pbp0qW0gkzJhGT4DsExr5OMB4mcVAcWZfUz/lEgqcl8TZ0LhD9bZi0sH5r9H?= =?us-ascii?Q?4y9lgsta+JZj7jAyy2XzWa1OXrxy1/Wk6RCRW2WlbdZKhd7mKPzex+XuVPDa?= =?us-ascii?Q?j1+dxSrrbP4yPy/z7/kP4FezciJezqs/qo30YTXBNeieNGha0IdzMN/pTwzb?= =?us-ascii?Q?5dkGRfybO52n+Zlzpcmle/aQTGiCqjcn9pUyKcx8ALhBGdajnyZnEqerNu8D?= =?us-ascii?Q?fEslpTF406UXyNOV0WgjlHNDfNNzhfWURU2ZyUXcdQTCpxHccXjEU66Js2z9?= =?us-ascii?Q?h2ikOFGeNkYw9/3FBGnUlGUKYqJc3jyf03DlF0IRo5s4JAt7iWrJPAMK6kRX?= =?us-ascii?Q?yoL6X7vsFh+Zl89kYzUkYb5fat6qBlP09GlmgAcdn+By+06UQ8At87vfA8Pt?= =?us-ascii?Q?/C39nEF3oDU615Z5KGyZLtA4UmJJzLZPzSIAIPvShyNm53ZBA7oAubxlW5PN?= =?us-ascii?Q?PrFJ+Svx2fUWnvElxVut6O3lH4HRo2DCWVa7noWhXVDbKtD947ICRSw4Gbrw?= =?us-ascii?Q?4RFFTb76SWYOumRxS56gRV6l2KWzdf6IdgJUfkCWURVZJ7JVrNasfFsO580Q?= =?us-ascii?Q?9R5EOste04UMl69CTWTEqIGibwgMSj195dUh88EjsezEpTSqxGVeKrj3LgbK?= =?us-ascii?Q?HaXalPYRE72hcrtGndSXNapu5k9del6KqQw+xtnZE9TEsmq3zMiuvLxZDkWc?= =?us-ascii?Q?WihTNSQ=3D?= Content-Type: text/plain; charset="us-ascii" Content-ID: MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SA1PR15MB5109.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 05b08b0c-c557-4239-a16e-08d96cc5c1bd X-MS-Exchange-CrossTenant-originalarrivaltime: 31 Aug 2021 21:24:46.2282 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: ZjYXsqCuttCOnmUNTEQOYwS3JIjJxxGR95urYw5g8EB+8LGM8hwcXyXB4rjS5SOPWHk9Ned20TRYQfhqXyHNFg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR15MB5096 X-OriginatorOrg: fb.com X-Proofpoint-GUID: Kt0W2pr8MH1xD8klOfsqrirsIoG3Q5lH X-Proofpoint-ORIG-GUID: Kt0W2pr8MH1xD8klOfsqrirsIoG3Q5lH X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-08-31_09:2021-08-31,2021-08-31 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 adultscore=0 impostorscore=0 clxscore=1015 malwarescore=0 spamscore=0 mlxlogscore=999 suspectscore=0 mlxscore=0 phishscore=0 bulkscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108310117 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Aug 31, 2021, at 9:41 AM, Song Liu wrote: > > > >> On Aug 31, 2021, at 8:32 AM, Peter Zijlstra wrote: >> >> On Mon, Aug 30, 2021 at 02:41:05PM -0700, Song Liu wrote: >> >>> @@ -564,6 +565,18 @@ static void notrace inc_misses_counter(struct bpf_prog *prog) >>> u64 notrace __bpf_prog_enter(struct bpf_prog *prog) >>> __acquires(RCU) >>> { >> preempt_disable_notrace(); >> >>> +#ifdef CONFIG_PERF_EVENTS >>> + /* Calling migrate_disable costs two entries in the LBR. To save >>> + * some entries, we call perf_snapshot_branch_stack before >>> + * migrate_disable to save some entries. This is OK because we >>> + * care about the branch trace before entering the BPF program. >>> + * If migrate happens exactly here, there isn't much we can do to >>> + * preserve the data. >>> + */ >>> + if (prog->call_get_branch) >>> + static_call(perf_snapshot_branch_stack)( >>> + this_cpu_ptr(&bpf_perf_branch_snapshot)); >> >> Here the comment is accurate, but if you recall the calling context >> requirements of perf_snapshot_branch_stack from the last patch, you'll >> see it requires you have at the very least preemption disabled, which >> you just violated. > >> >> I think you'll find that (on x86 at least) the suggested >> preempt_disable_notrace() incurs no additional branches. >> >> Still, there is the next point to consider... >> >>> +#endif >>> rcu_read_lock(); >>> migrate_disable(); >> >> preempt_enable_notrace(); > > Do we want preempt_enable_notrace() after migrate_disable()? It feels a > little weird to me. > >> >>> if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) { >> >>> @@ -1863,9 +1892,23 @@ void bpf_put_raw_tracepoint(struct bpf_raw_event_map *btp) >>> preempt_enable(); >>> } >>> >>> +DEFINE_PER_CPU(struct perf_branch_snapshot, bpf_perf_branch_snapshot); >>> + >>> static __always_inline >>> void __bpf_trace_run(struct bpf_prog *prog, u64 *args) >>> { >>> +#ifdef CONFIG_PERF_EVENTS >>> + /* Calling migrate_disable costs two entries in the LBR. To save >>> + * some entries, we call perf_snapshot_branch_stack before >>> + * migrate_disable to save some entries. This is OK because we >>> + * care about the branch trace before entering the BPF program. >>> + * If migrate happens exactly here, there isn't much we can do to >>> + * preserve the data. >>> + */ >>> + if (prog->call_get_branch) >>> + static_call(perf_snapshot_branch_stack)( >>> + this_cpu_ptr(&bpf_perf_branch_snapshot)); >>> +#endif >>> cant_sleep(); >> >> In the face of ^^^^^^ the comment makes no sense. Still, what are the >> nesting rules for __bpf_trace_run() and __bpf_prog_enter() ? I'm >> thinking the trace one can nest inside an occurence of prog, at which >> point you have pieces. > > I think broken LBR records is something we cannot really avoid in case > of nesting. OTOH, these should be rare cases and will not hurt the results > in most the use cases. > > I should probably tighten the rules in verifier to only apply it for > __bpf_prog_enter (where we have the primary use case). We can enable it > for other program types when there are other use cases. Update about some offline discussion with Alexei and Andrii. We are planning to move static_call(perf_snapshot_branch_stack) to inside the helper bpf_get_branch_snapshot. This change has a few benefit: 1. No need for extra check (prog->call_get_branch) before every program (even when the program doesn't use the helper). 2. No need to duplicate code of different BPF program hook. 3. BPF program always run with migrate_disable(), so it is not necessary to run add extra preempt_disable_notrace. It does flushes a few more LBR entries. But the result seems ok: ID: 0 from intel_pmu_lbr_disable_all+58 to intel_pmu_lbr_disable_all+93 ID: 1 from intel_pmu_lbr_disable_all+54 to intel_pmu_lbr_disable_all+58 ID: 2 from intel_pmu_snapshot_branch_stack+88 to intel_pmu_lbr_disable_all+0 ID: 3 from bpf_get_branch_snapshot+28 to intel_pmu_snapshot_branch_stack+0 ID: 4 from to bpf_get_branch_snapshot+0 ID: 5 from to ID: 6 from __bpf_prog_enter+34 to ID: 7 from migrate_disable+60 to __bpf_prog_enter+9 ID: 8 from __bpf_prog_enter+4 to migrate_disable+0 ID: 9 from __bpf_prog_enter+4 to __bpf_prog_enter+0 ID: 10 from bpf_fexit_loop_test1+22 to __bpf_prog_enter+0 ID: 11 from bpf_fexit_loop_test1+20 to bpf_fexit_loop_test1+13 ID: 12 from bpf_fexit_loop_test1+20 to bpf_fexit_loop_test1+13 ID: 13 from bpf_fexit_loop_test1+20 to bpf_fexit_loop_test1+13 ID: 14 from bpf_fexit_loop_test1+20 to bpf_fexit_loop_test1+13 ID: 15 from bpf_fexit_loop_test1+20 to bpf_fexit_loop_test1+13 We can save more by inlining intel_pmu_lbr_disable_all(). But it is probably not necessary at the moment. Thanks, Song