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Tue, 10 Dec 2019 18:19:32 +0000 Received: from MN2PR15MB3213.namprd15.prod.outlook.com ([fe80::6d1e:f2f7:d36:a42f]) by MN2PR15MB3213.namprd15.prod.outlook.com ([fe80::6d1e:f2f7:d36:a42f%4]) with mapi id 15.20.2516.018; Tue, 10 Dec 2019 18:19:32 +0000 From: Martin Lau To: Paul Chaignon CC: Paul Burton , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , Mahshid Khezri , "paul.chaignon@gmail.com" , "bpf@vger.kernel.org" , "netdev@vger.kernel.org" , Alexei Starovoitov , Daniel Borkmann , Song Liu , Yonghong Song , Andrii Nakryiko Subject: Re: [PATCH bpf 0/2] Limit tail calls to 33 in all JIT compilers Thread-Topic: [PATCH bpf 0/2] Limit tail calls to 33 in all JIT compilers Thread-Index: AQHVrsHC45KQMgUrPkOrjfAD1N39MqezrzWA Date: Tue, 10 Dec 2019 18:19:32 +0000 Message-ID: <20191210181929.477nstc4vcccecyc@kafai-mbp> References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-clientproxiedby: MWHPR15CA0042.namprd15.prod.outlook.com (2603:10b6:300:ad::28) To MN2PR15MB3213.namprd15.prod.outlook.com (2603:10b6:208:3d::12) x-ms-exchange-messagesentrepresentingtype: 1 x-originating-ip: [2620:10d:c090:200::1:85a] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 435ed96e-f86e-4bd6-3c51-08d77d9d80f4 x-ms-traffictypediagnostic: MN2PR15MB2703: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:8273; 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charset="iso-8859-1" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 435ed96e-f86e-4bd6-3c51-08d77d9d80f4 X-MS-Exchange-CrossTenant-originalarrivaltime: 10 Dec 2019 18:19:32.5230 (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: vJF3dCZGckj+LQViSf5Vd8LIryfzDyzAa7vymIPezMpR+Ka44EFciEolGkNL46p5 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR15MB2703 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-12-10_05:2019-12-10,2019-12-10 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxscore=0 phishscore=0 bulkscore=0 lowpriorityscore=0 malwarescore=0 impostorscore=0 suspectscore=0 adultscore=0 spamscore=0 clxscore=1011 mlxlogscore=577 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1912100153 X-FB-Internal: deliver Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Dec 09, 2019 at 07:51:52PM +0100, Paul Chaignon wrote: > The BPF interpreter and all JIT compilers, except RISC-V's and MIPS', > enforce a 33-tail calls limit at runtime. Because of this discrepancy, a > BPF program can have a different behavior and output depending on whether > it is interpreted or JIT compiled, or depending on the underlying > architecture. >=20 > This patchset changes the RISC-V and MIPS JIT compilers to limit tail > calls to 33 instead of 32. I have checked other BPF JIT compilers for th= e > same discrepancy. Acked-by: Martin KaFai Lau