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b=W06/Okp2+6X9taW9ubITosSrjQe70eS7o9OiOuV5pvxFfosKwTTd823BPraGPtMq7LkrSOkiCod4KYpD1QTnmoeZRINSV4GKvNPKffQuGLx5d8v5XjhbWirFzg7tKTBKAAnw7UwBdPveH+fGMBqGIZYXYA5YPvWTQx4STYhtMos= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from BL1PR12MB5320.namprd12.prod.outlook.com (2603:10b6:208:314::17) by IA0PR12MB8225.namprd12.prod.outlook.com (2603:10b6:208:408::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.315.12; Wed, 12 Aug 2026 22:57:42 +0000 Received: from BL1PR12MB5320.namprd12.prod.outlook.com ([fe80::1876:4a6d:2cf5:b8d1]) by BL1PR12MB5320.namprd12.prod.outlook.com ([fe80::1876:4a6d:2cf5:b8d1%5]) with mapi id 15.21.0315.012; Wed, 12 Aug 2026 22:57:42 +0000 Message-ID: <924aedc6-c2dc-4c09-84d5-2bdf1370ab36@amd.com> Date: Wed, 12 Aug 2026 17:57:38 -0500 User-Agent: Mozilla Thunderbird Subject: Re: [RESEND PATCH v4 08/15] fs/resctrl: Add interface to display supported and active kernel-mode policy To: Reinette Chatre , Babu Moger , corbet@lwn.net, tony.luck@intel.com, Dave.Martin@arm.com, james.morse@arm.com, tglx@kernel.org, bp@alien8.de, ben.horgan@arm.com, fenghuay@nvidia.com Cc: skhan@linuxfoundation.org, x86@kernel.org, mingo@redhat.com, dave.hansen@linux.intel.com, hpa@zytor.com, akpm@linux-foundation.org, rdunlap@infradead.org, peterz@infradead.org, feng.tang@linux.alibaba.com, dapeng1.mi@linux.intel.com, elver@google.com, enelsonmoore@gmail.com, kuba@kernel.org, ebiggers@kernel.org, lirongqing@baidu.com, seanjc@google.com, nikunj@amd.com, xin@zytor.com, pawan.kumar.gupta@linux.intel.com, tiala@microsoft.com, chang.seok.bae@intel.com, kprateek.nayak@amd.com, prathyushi.nangia@amd.com, kim.phillips@amd.com, naveen@kernel.org, darwi@linutronix.de, elena.reshetova@intel.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, thomas.lendacky@amd.com, eranian@google.com, peternewman@google.com, qinyuntan@linux.alibaba.com References: <328e237e-3d26-47c0-8167-8ffe5d765daf@intel.com> Content-Language: en-US From: "Moger, Babu" In-Reply-To: <328e237e-3d26-47c0-8167-8ffe5d765daf@intel.com> Content-Type: text/plain; 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Generic >> resctrl tracks the supported policies, the active policy, and the resctrl >> group backing any global assignment policy. However, this information is >> not exposed to user space. >> >> Introduce a new resctrl file, info/kernel_mode, to expose the global >> kernel-mode policy and its associated resource group (when applicable). >> This read-only sysfs file lists all supported policies, one per line, and >> highlights the active policy using square brackets. > > (please rewrite with consistent terms) > Sure. >> >> Signed-off-by: Babu Moger > > > >> +/** >> + * resctrl_kernel_mode_show() - Display supported and active kernel-mode policies >> + * @of: kernfs open file >> + * @seq: output seq_file >> + * @v: unused >> + * >> + * Displays one line per mode set in resctrl_kcfg.kmode. Bracket the active >> + * policy (resctrl_kcfg.kmode_cur). >> + * >> + * INHERIT_CTRL_AND_MON is displayed as "[inherit_ctrl_and_mon]" when active >> + * or "inherit_ctrl_and_mon" when supported but inactive, with no :group= >> + * suffix in either case. >> + * >> + * Global-assign modes append :group=. An inactive mode is emitted as >> + * ":group=uninitialized". An active mode with a bound group is emitted >> + * as "[:group=//]", where // is derived from >> + * resctrl_kcfg.k_rdtgrp. >> + * >> + * Return: 0 on success, or -ENOENT on error. >> + */ >> +static int resctrl_kernel_mode_show(struct kernfs_open_file *of, >> + struct seq_file *seq, void *v) >> +{ >> + enum resctrl_kernel_mode mode; >> + struct rdtgroup *rdtgrp; >> + const char *ctrl, *mon; >> + bool active; >> + int ret = 0; >> + >> + mutex_lock(&rdtgroup_mutex); > > The changes to make resctrl more robust have since been merged. Please consider: > 2d77f9768850 ("fs/resctrl: Prevent deadlock and use-after-free in info file handlers") > > When you rebase, please use the new info_kn_lock()/info_kn_unlock() helpers. Sure. Will do. > >> + for (mode = 0; mode < RESCTRL_NUM_KERNEL_MODES; mode++) { >> + if (!test_bit(mode, &resctrl_kcfg.kmode)) >> + continue; >> + >> + active = (resctrl_kcfg.kmode_cur == mode); >> + >> + if (mode == INHERIT_CTRL_AND_MON) { >> + seq_printf(seq, active ? "[%s]\n" : "%s\n", >> + resctrl_mode_str[mode]); >> + continue; >> + } >> + >> + if (!active) { >> + seq_printf(seq, "%s:group=uninitialized\n", >> + resctrl_mode_str[mode]); >> + continue; >> + } >> + >> + /* >> + * There should be a valid group when any of the global >> + * assign mode is active; otherwise, report an error. > > This would indicate a resctrl bug, no? Yes. > >> + */ >> + rdtgrp = resctrl_kcfg.k_rdtgrp; >> + if (!rdtgrp) { >> + ret = -ENOENT; >> + goto out_unlock; > > If this fails there needs to be content in last_cmd_status. Otherwise this > fails and then last_cmd_status reads "ok" or worse .. an old failure message. if (WARN_ON(!rdtgrp)) { rdt_last_cmd_puts("Invalid kernel mode group\n"); ret = -ENOENT; goto out_unlock; } Thanks Babu