From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.55.52.115]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BE75047376 for ; Tue, 10 Oct 2023 13:37:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="NcaBTHCa" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1696945061; x=1728481061; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=XxupxmtyB6MfsqYIPevKjc8Mkmjyag2c1qs/SolrDdo=; b=NcaBTHCaJnFpf/KRspbxJx6yxaw7m+ElYXQS2qJDzdUimfaD8YUX88lA IQcYKtqqXMCM59DPKQAfCESEZufOaysmI+Cl0iMlYheIKhweR9tiGOChq J4P1kKwOqsDbjC9dCWAkQwR3qnMBF/XUZbczoR0n+L/zGKXfH9pOOr308 VVIJ/Rznmgo3fA0eNQm+8bzc0VwGN7h7oZ5Qjg8vofla/qxpCBbA+Kk+P v5t7IDI8whCId1bbKFKjEbxcRdj4IUzJiNpf/YXTB900YoSpFq/aX3RJM 6IcBlSy5Fe5NZKQTAfIKA+ze8B6mLS/HiZfTA7DFSnctlGt3GaIxaxOEj w==; X-IronPort-AV: E=McAfee;i="6600,9927,10859"; a="384250787" X-IronPort-AV: E=Sophos;i="6.03,212,1694761200"; d="scan'208";a="384250787" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Oct 2023 06:35:59 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10859"; a="747072144" X-IronPort-AV: E=Sophos;i="6.03,212,1694761200"; d="scan'208";a="747072144" Received: from patinira-mobl.amr.corp.intel.com (HELO [10.212.128.216]) ([10.212.128.216]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Oct 2023 06:35:59 -0700 Message-ID: Date: Tue, 10 Oct 2023 06:35:59 -0700 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 02/13] kernel/cpu: Add support for declaring CPU hotplug not supported Content-Language: en-US To: "Kirill A. Shutemov" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org Cc: "Rafael J. Wysocki" , Peter Zijlstra , Adrian Hunter , Elena Reshetova , Jun Nakajima , Rick Edgecombe , Tom Lendacky , kexec@lists.infradead.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org References: <20231005131402.14611-1-kirill.shutemov@linux.intel.com> <20231005131402.14611-3-kirill.shutemov@linux.intel.com> From: Kuppuswamy Sathyanarayanan In-Reply-To: <20231005131402.14611-3-kirill.shutemov@linux.intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/5/2023 6:13 AM, Kirill A. Shutemov wrote: > The function cpu_hotplug_not_supported() can be called to indicate that > CPU hotplug should be disabled. It does not prevent the initial bring up > of the CPU, but it stops subsequent offlining. > > This function is intended to replace CC_ATTR_HOTPLUG_DISABLED. > Looks good to me. Reviewed-by: Kuppuswamy Sathyanarayanan > Signed-off-by: Kirill A. Shutemov > --- > include/linux/cpu.h | 2 ++ > kernel/cpu.c | 17 ++++++++++++++++- > 2 files changed, 18 insertions(+), 1 deletion(-) > > diff --git a/include/linux/cpu.h b/include/linux/cpu.h > index f19f56501809..aab3887cadbc 100644 > --- a/include/linux/cpu.h > +++ b/include/linux/cpu.h > @@ -132,6 +132,7 @@ extern void cpus_read_lock(void); > extern void cpus_read_unlock(void); > extern int cpus_read_trylock(void); > extern void lockdep_assert_cpus_held(void); > +extern void cpu_hotplug_not_supported(void); > extern void cpu_hotplug_disable(void); > extern void cpu_hotplug_enable(void); > void clear_tasks_mm_cpumask(int cpu); > @@ -147,6 +148,7 @@ static inline void cpus_read_lock(void) { } > static inline void cpus_read_unlock(void) { } > static inline int cpus_read_trylock(void) { return true; } > static inline void lockdep_assert_cpus_held(void) { } > +static inline void cpu_hotplug_not_supported(void) { } > static inline void cpu_hotplug_disable(void) { } > static inline void cpu_hotplug_enable(void) { } > static inline int remove_cpu(unsigned int cpu) { return -EPERM; } > diff --git a/kernel/cpu.c b/kernel/cpu.c > index 6de7c6bb74ee..cf536fe1a88a 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -484,6 +484,9 @@ static int cpu_hotplug_disabled; > > DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock); > > +/* Cleared if platform declares CPU hotplug not supported */ > +static bool cpu_hotplug_supported = true; > + > void cpus_read_lock(void) > { > percpu_down_read(&cpu_hotplug_lock); > @@ -543,6 +546,18 @@ static void lockdep_release_cpus_lock(void) > rwsem_release(&cpu_hotplug_lock.dep_map, _THIS_IP_); > } > > +/* > + * Declare CPU hotplug not supported. > + * > + * It doesn't prevent initial bring up of the CPU, but stops offlining. > + */ > +void cpu_hotplug_not_supported(void) > +{ > + cpu_maps_update_begin(); > + cpu_hotplug_supported = false; > + cpu_maps_update_done(); > +} Since this function is not used in this patch, do you need to add __maybe_unused to avoid warnings? > + > /* > * Wait for currently running CPU hotplug operations to complete (if any) and > * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects > @@ -1507,7 +1522,7 @@ static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target) > * If the platform does not support hotplug, report it explicitly to > * differentiate it from a transient offlining failure. > */ > - if (cc_platform_has(CC_ATTR_HOTPLUG_DISABLED)) > + if (cc_platform_has(CC_ATTR_HOTPLUG_DISABLED) || !cpu_hotplug_supported) > return -EOPNOTSUPP; > if (cpu_hotplug_disabled) > return -EBUSY; -- Sathyanarayanan Kuppuswamy Linux Kernel Developer