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Mon, 30 Nov 2020 17:20:39 +0000 Subject: Re: [PATCH v2 bpf-next 11/13] bpf: Add bitwise atomic instructions To: Alexei Starovoitov CC: Brendan Jackman , , Alexei Starovoitov , Daniel Borkmann , KP Singh , Florent Revest , , Jann Horn References: <20201127175738.1085417-1-jackmanb@google.com> <20201127175738.1085417-12-jackmanb@google.com> <20201129013615.mf45ihcio2abuvlu@ast-mbp> From: Yonghong Song Message-ID: <57c39719-06e6-17cf-32d4-70869f6618a5@fb.com> Date: Mon, 30 Nov 2020 09:20:34 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 In-Reply-To: <20201129013615.mf45ihcio2abuvlu@ast-mbp> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [2620:10d:c090:400::5:5f96] X-ClientProxiedBy: CO1PR15CA0086.namprd15.prod.outlook.com (2603:10b6:101:20::30) To BYAPR15MB4088.namprd15.prod.outlook.com (2603:10b6:a02:c3::18) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [IPv6:2620:10d:c085:21cf::124e] (2620:10d:c090:400::5:5f96) by CO1PR15CA0086.namprd15.prod.outlook.com (2603:10b6:101:20::30) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3611.20 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?THd6WkJnM0p2dThWVTZJOXZlelRCNmpzeFJ0NXNjQmYxWnVucStPdlNZNW9r?= =?utf-8?B?c2hUWCtjOUhQQUhuSmNiTEpDK3pWM2xLYjZTLzA3ZmdIWFhMdmEycENJRzFI?= =?utf-8?B?ellyaHExay9sK1FmTndoMDVRcTZsd0ZuY0c4V0l2RTNsZG1NblJxMmM5SUk5?= =?utf-8?B?djBxa21XYmhQeGZ5ZFZ1a3h0QjdQUUpiQ2UzdWFaN3NLTGNwRjREV1VZTGxZ?= =?utf-8?B?MlAxTGwyOGhYc09hS2FkdW8wdW4wUVFETjI1YTR6RGN1bmtuTGVSNWdKbkcr?= =?utf-8?B?OVpxL0ZEZnE3cGpnNk00ajF4VTB3WWY3d3ZtclRZcFIydTZYaVFmc21mTnZh?= =?utf-8?B?aEFFSkVaUHR5RVlLcGpvWTVzMHlSZG01MXhjaTY4YkFZU0tVTWNSWUlvZGR0?= =?utf-8?B?cTBCemltS2pKZ0o5SllOYWJONmNReG9FTHFYdDZGbFBTMnZzZnMvQ1MxM3Uz?= =?utf-8?B?ZThvVUlESmNVd0N1T3RVcXk2NVR3eTNKWkJoRXBacVVob094VXhhL25CSUFY?= =?utf-8?B?RXdaWS9WcnpkZ0cyeC9qMHRteGVZRWF6SlRLTWxjbzB5bFpZL01CZklLeXk1?= =?utf-8?B?cC96dEF5RzhqQk41T2MwNnZOQml6WEJWL2txQTNpTDBkV2NueG0rYlNwQ0Nr?= =?utf-8?B?NlpXYUNJRDhIQlUyUmI3SEJvSk5vSmNEdlBqNm9vekx5L3l3Q0FaRXBwQXNW?= =?utf-8?B?U3NKb3ZiYjBxVGFvWjdoNGtQSEZiSmZNMEovNDh5MmlDTlF1Q2FPczdKMDhV?= =?utf-8?B?cU9YVWp5UjVibndiZ0hoMHZvMlhTOTNwZ3FyU1Y4eDVELy9OcC92L1JZWlZw?= =?utf-8?B?dGk5THhNbXovUDZXcjMzd0ZQSWNtTENNRlczUHpQdnVoSTYvVXM1eXJMT3lC?= =?utf-8?B?UzFSTUJHUXlETVRJQkdnKzltdVY4YjBPZGY5WVpzVllFSXhpQmREZzZRUTJ1?= =?utf-8?B?eDdpQVA3NFRSYmhDVDVEMkZtVzNsTFRRQVF4dS95WnNyZDlSb2lHSW05QVIz?= =?utf-8?B?V1RZcUxxdHV4K2wwSnpSbU8rRmE1blZzeTdnOWUwQkVnYjFic1lpMlJWMnAz?= =?utf-8?B?TWxuTjl0NGNYY0thaHJCMy9pV0pZSWRzUW9MVFdaSXBpZ3ZYMU5mVVVkSnRu?= =?utf-8?B?elpsSDVBVUo0UENoNjJ4ZDg3U09ENW93UXFjcnZVK2xoSjRKTnJsVEVmUFpU?= =?utf-8?B?MUpkNVp4NkR3aFRreHh5TDRkR3IrT0wxYnNjSWtnWXdkWldWdE9MNUo4Z21a?= =?utf-8?B?a1VUTlYzM1REdFloUHkrMDRsZGIwTWJHU0xGalAvV01yTlI2Y3ZyOU54Umor?= =?utf-8?B?MVJJa2d2TGUybXByeUdpQmgzSkFNTGhQanR6cGYzTGdZdXVLLzJWcUR3L285?= =?utf-8?B?VXg2cldYMExpZ2c9PQ==?= X-MS-Exchange-CrossTenant-Network-Message-Id: f695335b-3f37-496a-fdc2-08d8955441e2 X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB4088.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Nov 2020 17:20:38.9740 (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: x0hUYxGfK4lp4aM6aGcpQzMm7Qc/7F0ycEtOn2DzKoYAMf49KQCMrxB97/xw/dKf X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB3047 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-11-30_06:2020-11-30,2020-11-30 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 adultscore=0 lowpriorityscore=0 priorityscore=1501 impostorscore=0 bulkscore=0 mlxscore=0 spamscore=0 mlxlogscore=840 malwarescore=0 suspectscore=0 clxscore=1015 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011300112 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/28/20 5:36 PM, Alexei Starovoitov wrote: > On Fri, Nov 27, 2020 at 09:39:10PM -0800, Yonghong Song wrote: >> >> >> On 11/27/20 9:57 AM, Brendan Jackman wrote: >>> This adds instructions for >>> >>> atomic[64]_[fetch_]and >>> atomic[64]_[fetch_]or >>> atomic[64]_[fetch_]xor >>> >>> All these operations are isomorphic enough to implement with the same >>> verifier, interpreter, and x86 JIT code, hence being a single commit. >>> >>> The main interesting thing here is that x86 doesn't directly support >>> the fetch_ version these operations, so we need to generate a CMPXCHG >>> loop in the JIT. This requires the use of two temporary registers, >>> IIUC it's safe to use BPF_REG_AX and x86's AUX_REG for this purpose. >> >> similar to previous xsub (atomic[64]_sub), should we implement >> xand, xor, xxor in llvm? > > yes. please. Unlike atomic_fetch_sub that can be handled by llvm. > atomic_fetch_or/xor/and has to be seen as separate instructions > because JITs will translate them as loop. Okay, will try to implement xsub, xand, xor and xxor in llvm.