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Wed, 25 Feb 2026 06:23:28 +0000 Received: from smtpav02.fra02v.mail.ibm.com (smtpav02.fra02v.mail.ibm.com [10.20.54.101]) by smtprelay02.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 61P6NQeT49283526 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 25 Feb 2026 06:23:27 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DA21920043; Wed, 25 Feb 2026 06:23:26 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5FAE020040; Wed, 25 Feb 2026 06:23:25 +0000 (GMT) Received: from [9.124.223.55] (unknown [9.124.223.55]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 25 Feb 2026 06:23:25 +0000 (GMT) Message-ID: <4cd8aeab-615a-4066-a573-5e50e7e7aad5@linux.ibm.com> Date: Wed, 25 Feb 2026 11:53:24 +0530 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [Linux PPC] Disable PREEMPT To: Christian Zigotzky , linuxppc-dev , "kvm-ppc@vger.kernel.org" , Madhavan Srinivasan Cc: "R.T.Dickinson" , hypexed@yahoo.com.au, mad skateman , Christian Zigotzky References: <185d7a42-f7b4-44e1-a129-f5989d211c74@linux.ibm.com> <40154f6a-39da-959d-e039-5ab9ff62db3c@xenosoft.de> <709b864f-9daa-4a48-b3d6-39baedce63b2@linux.ibm.com> <843b7c60-23f1-47d0-b4e8-2147c3e40c23@linux.ibm.com> <2a27e6fc-7eb4-41a5-ba88-58f6a22625b5@xenosoft.de> <1d79ec6f-ce7f-4432-80e0-a54fa1668642@linux.ibm.com> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: Content-Type: text/plain; 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Is this sent as a patch or just a reply to the thread? If it is sent as patch, Please follow these guidelines. https://docs.kernel.org/process/submitting-patches.html On 2/25/26 11:24 AM, Christian Zigotzky wrote: > Hello, > > We were previously able to disable PREEMPT in the kernel configuration, > but the latest kernels now enable it by default and it is no longer > possible to disable it. > > Is it possible to let us decide whether to activate PREEMPT or not? > > Currently we use the following revert patch for our non-preempt kernels. > > --- a/kernel/Kconfig.preempt    2026-02-14 10:06:32.000000000 +0000 > +++ b/kernel/Kconfig.preempt    2026-02-08 21:03:27.000000000 +0000 > @@ -16,13 +16,11 @@ config ARCH_HAS_PREEMPT_LAZY > >  choice >      prompt "Preemption Model" > -    default PREEMPT_LAZY if ARCH_HAS_PREEMPT_LAZY >      default PREEMPT_NONE > >  config PREEMPT_NONE >      bool "No Forced Preemption (Server)" >      depends on !PREEMPT_RT > -    depends on ARCH_NO_PREEMPT >      select PREEMPT_NONE_BUILD if !PREEMPT_DYNAMIC >      help >        This is the traditional Linux preemption model, geared towards > @@ -37,7 +35,6 @@ config PREEMPT_NONE > >  config PREEMPT_VOLUNTARY >      bool "Voluntary Kernel Preemption (Desktop)" > -    depends on !ARCH_HAS_PREEMPT_LAZY >      depends on !ARCH_NO_PREEMPT >      depends on !PREEMPT_RT >      select PREEMPT_VOLUNTARY_BUILD if !PREEMPT_DYNAMIC > I would instead fix any issue we have in PREEMPT FULL/LAZY rather than falling back to old methods. btw, did the previous patch sent, which you said helps you to boot, can you confirm it did help you? If yes, i can send it as patch, since cond_resched if called from boot cpu might be stuck in the loop forever. IIRC, after boot, you had some driver causing crash. If so, share backtrace of the crash? If you don't use that driver, is the guest stable?