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Fri, 4 Dec 2020 15:21:24 +0000 Subject: Re: [PATCH bpf-next v3 10/14] bpf: Add bitwise atomic instructions To: Brendan Jackman CC: , Alexei Starovoitov , Daniel Borkmann , KP Singh , Florent Revest , , Jann Horn References: <20201203160245.1014867-1-jackmanb@google.com> <20201203160245.1014867-11-jackmanb@google.com> <86a88eba-83a1-93c0-490d-ceba238e3aad@fb.com> From: Yonghong Song Message-ID: <534a6371-a5ed-2459-999b-90b8a8b773e8@fb.com> Date: Fri, 4 Dec 2020 07:21:22 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 In-Reply-To: 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:fab1] X-ClientProxiedBy: MW3PR05CA0015.namprd05.prod.outlook.com (2603:10b6:303:2b::20) 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:c085:21c8::12b3] (2620:10d:c090:400::5:fab1) by MW3PR05CA0015.namprd05.prod.outlook.com (2603:10b6:303:2b::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3654.7 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?U0NBZ1VjRE1jNFpvRG56L3ZWNU9LVGR3UDJxS2J5MGlhVVN4SVNESVlnMkli?= =?utf-8?B?R1lnYmZ3dDh3ZFcrWjdKSHE1SnBnMyt3L25aWmtUb3Y1WjBOVnUvS0FEeGR6?= =?utf-8?B?RVdwNVJUaWxDN3lnQ29IK3VHZEpqb3BKM2RrT0hOSGRWeU9hWTdjVFlJUyti?= =?utf-8?B?eTFLc0Q5dndTRXdNV0w2V0FFNGxrazB1ZXV6ZHV5S0w5bmxVZkVOK0JTWWkw?= =?utf-8?B?UHFIdUQrbm9qQzVKMFhtNHpKWWhpbURUTzlBejhRNnF5eitVbmlNZGxaZ3Ex?= =?utf-8?B?ZUNqancxWWxockNxTGNzWjhhUHZxV0Y4MnFiTkFzSUdUd011NStMQmtYZk16?= =?utf-8?B?WkVXUGMvbHpRNURuVmV1aTFZdm93ZnNMMDEvTUNyTHdRNXpOSnRuWDJIMStq?= =?utf-8?B?b01TWllIb01yQitjVDA2SEhJQVpjZjIyTktOSmJ2T2l0UjBXOHFpcTdMVDJP?= =?utf-8?B?RGUrUll6YjNSREdnZ2dEdWVFY2J6K0toOEIxNDhEOC91TCtITmE1aTI3MVhz?= =?utf-8?B?S3ZqV2tCYmIxUmtJalloVkJ5ZWVSRy9CRC9xbGVYVmpNdFNRT3BBczBGUlJm?= =?utf-8?B?VElOdVVxOVlzMkdtRldSNVV5T2hxSFNJRmdaL2dHSW00aGVzT3RPcTBNQ3kv?= =?utf-8?B?OE1NOHlvWVR4TUwzQkhQZzVETlQ5Tk5KNnFUQ0swK29EaU5jdTY0dHpPR0R4?= =?utf-8?B?Q1Bmczh0aEg3ckZCa2VxSWU4SjY3eWx6MGY3cXI3b3JiRi9haTdndk92Rzc2?= =?utf-8?B?RTZ1U1ROQzA0ZkJMMENYUlg2eDBtT3VldTd0QlZuMWV5cXhIemhVbWtVd2g1?= =?utf-8?B?UHIySHpvS2tYTEdBVmNwOHk4akZzajRvZitqYXNHalNiekw4UFRKYzNJVDdp?= =?utf-8?B?R1pWRUxYa1U2ekkrV1VPK3E4TGZ6Y21GTmRXamt3ZXVzTC9YSENyM3NxT3V1?= =?utf-8?B?aHkwZzNnRUV3RFEwR2piVG01UE9TZ1lReGlFVkhQVFpGMEdrY3pZOXBVVzJG?= =?utf-8?B?aHNpYVh5bTcwdEc3Wm1mclNMb2JBdklBNURuQnJabG9OdGhKUFg5UTlHYUE5?= =?utf-8?B?WnJYLzlKOWNNM1FvYlBDbmpuSUNlV1NJV1Y1eFE1YkxuQk1tVUxDSml0Q1pz?= =?utf-8?B?Z0RrV0VVd25iQVpLN3E1eXJJRWlkL1RzMzdUNE9tekRaVDRIb3Q0dGZvc2I5?= =?utf-8?B?bkVUQjR0NnZDaWx1U1VucVJBaFBvRlZja1JQQzJycUNBVU9kcmZTOFEvNVA0?= =?utf-8?B?QjErd0xEUDBCeW56WDlFMTFLMitOYXpqN1ppajkyZ3FHY3BrN0pjTzhTb21T?= =?utf-8?B?c2U5NFhBd0J5OTFQSGR6TDJvMjFnSlZjdE95aTluZWs4MFVXMnZFQlA2aTlD?= =?utf-8?B?ZU9SaFMxRDdFZkE9PQ==?= X-MS-Exchange-CrossTenant-Network-Message-Id: bedc9bfc-7d07-468f-3ab6-08d898684356 X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB4088.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Dec 2020 15:21:24.8549 (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: 3YBHHx02lqiIJ199qTRKOO2B7HlY9U3OV2aZDf3MpDLvIywHV0PjuczcKEMGOtyV X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2408 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-12-04_05:2020-12-04,2020-12-04 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 bulkscore=0 adultscore=0 priorityscore=1501 spamscore=0 mlxlogscore=999 mlxscore=0 clxscore=1015 impostorscore=0 lowpriorityscore=0 malwarescore=0 phishscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012040089 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/4/20 1:36 AM, Brendan Jackman wrote: > On Thu, Dec 03, 2020 at 10:42:19PM -0800, Yonghong Song wrote: >> >> >> On 12/3/20 8:02 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. >>> >>> Change-Id: I340b10cecebea8cb8a52e3606010cde547a10ed4 >>> Signed-off-by: Brendan Jackman >>> --- >>> arch/x86/net/bpf_jit_comp.c | 50 +++++++++++++++++++++++++++++- >>> include/linux/filter.h | 60 ++++++++++++++++++++++++++++++++++++ >>> kernel/bpf/core.c | 5 ++- >>> kernel/bpf/disasm.c | 21 ++++++++++--- >>> kernel/bpf/verifier.c | 6 ++++ >>> tools/include/linux/filter.h | 60 ++++++++++++++++++++++++++++++++++++ >>> 6 files changed, 196 insertions(+), 6 deletions(-) >>> > [...] >>> diff --git a/include/linux/filter.h b/include/linux/filter.h >>> index 6186280715ed..698f82897b0d 100644 >>> --- a/include/linux/filter.h >>> +++ b/include/linux/filter.h >>> @@ -280,6 +280,66 @@ static inline bool insn_is_zext(const struct bpf_insn *insn) > [...] >>> +#define BPF_ATOMIC_FETCH_XOR(SIZE, DST, SRC, OFF) \ >>> + ((struct bpf_insn) { \ >>> + .code = BPF_STX | BPF_SIZE(SIZE) | BPF_ATOMIC, \ >>> + .dst_reg = DST, \ >>> + .src_reg = SRC, \ >>> + .off = OFF, \ >>> + .imm = BPF_XOR | BPF_FETCH }) >>> + >>> /* Atomic exchange, src_reg = atomic_xchg((dst_reg + off), src_reg) */ >> >> Looks like BPF_ATOMIC_XOR/OR/AND/... all similar to each other. >> The same is for BPF_ATOMIC_FETCH_XOR/OR/AND/... >> >> I am wondering whether it makes sence to have to >> BPF_ATOMIC_BOP(BOP, SIZE, DST, SRC, OFF) and >> BPF_ATOMIC_FETCH_BOP(BOP, SIZE, DST, SRC, OFF) >> can have less number of macros? > > Hmm yeah I think that's probably a good idea, it would be consistent > with the macros for non-atomic ALU ops. > > I don't think 'BOP' would be very clear though, 'ALU' might be more > obvious. BPF_ATOMIC_ALU and BPF_ATOMIC_FETCH_ALU indeed better. >