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charset="us-ascii" Content-ID: <7C41E9A474116749983E4FE6CC00F5E5@namprd15.prod.outlook.com> 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: 6dc97563-9558-4d8e-8922-08d96efc01c0 X-MS-Exchange-CrossTenant-originalarrivaltime: 03 Sep 2021 16:58:08.8700 (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: edXALkgvVgRgHCsCgjq+UyEe3shK5SrZuTDG0V3synLiUkDj44HZGmH+ON3vUOtDNG1gJwI/hvIo+Fm8PNTV/Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR15MB5078 X-OriginatorOrg: fb.com X-Proofpoint-ORIG-GUID: VpDny3GaWG8M3MDSWMUW8eEh_YmfbXtm X-Proofpoint-GUID: VpDny3GaWG8M3MDSWMUW8eEh_YmfbXtm X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-09-03_07:2021-09-03,2021-09-03 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 bulkscore=0 impostorscore=0 priorityscore=1501 mlxscore=0 adultscore=0 lowpriorityscore=0 malwarescore=0 clxscore=1015 suspectscore=0 spamscore=0 mlxlogscore=999 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2108310000 definitions=main-2109030100 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Sep 3, 2021, at 1:28 AM, Peter Zijlstra wrote: > > On Thu, Sep 02, 2021 at 09:57:05AM -0700, Song Liu wrote: >> +BPF_CALL_3(bpf_get_branch_snapshot, void *, buf, u32, size, u64, flags) >> +{ >> +#ifndef CONFIG_X86 >> + return -ENOENT; >> +#else >> + static const u32 br_entry_size = sizeof(struct perf_branch_entry); >> + u32 entry_cnt = size / br_entry_size; >> + >> + if (unlikely(flags)) >> + return -EINVAL; >> + >> + if (!buf || (size % br_entry_size != 0)) >> + return -EINVAL; >> + >> + entry_cnt = static_call(perf_snapshot_branch_stack)(buf, entry_cnt); >> + >> + if (!entry_cnt) >> + return -ENOENT; >> + >> + return entry_cnt * br_entry_size; >> +#endif >> +} > > Do we really need that CONFIG_X86 thing? Seems rather bad practise. The ifndef will save a few cycles on architectures that do not support branch stack. I personally don't have very strong preference on either way. Thanks, Song