From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 EB96F2D374F for ; Wed, 25 Feb 2026 07:16:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772003811; cv=none; b=jwxLvlXj2tj2NfAUtisnJnvuOgGh5poTQ52eIUMN4fPBy7UC1DVW/ZmpB+R1mddRlybsfokBTwEnHITK7r6JCoupFxgcSj5Aa75aN7SCK/7Rv1pGPlSRw+4T2QDKjPG/nYONj1YcuIpV5dhnwgrVncu0zWhvIr+Ba808n3fscsw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772003811; c=relaxed/simple; bh=0VoyvgVLV83OpwaPy00QzkStcLMj9l0dy7bXC5TxxWk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pDDsR77kk706RTswtDaqJz+4wrXWZ80dy5EELUhtCo1X5lGV9MTZwHmPmyyBqXrFqGSnu5yShy/OyJPUwttcNy06V+CUDd2NF9YCM7BPkhDcPnJcMMtDqd3z8leshRuyZ0bG8iSdsbaVm/uRRzmZvFOrXSkrcCnX8z7e2Fe5GMo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HhGHbd6J; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HhGHbd6J" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BAC70C116D0; Wed, 25 Feb 2026 07:16:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772003810; bh=0VoyvgVLV83OpwaPy00QzkStcLMj9l0dy7bXC5TxxWk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=HhGHbd6JJH07IUaYX046Ao6B9dcliOfhUr1xO4B9pi4R9bqN/800FOrs8kWtviVaW EJSoKix0cJj7MQfzNR0CLmBs8XAQ66BNJga4ZmUrRV6bKiK+NyfbvowfNf5zZpnnOV k6olCvKiYPjiWNDrXDa4ZYkeg+E6Fz3cBr1aflSx1LwWFmAxdbDU7qs36hf65VJxwQ ylR+vpwFMTeKAZpsgVktRwO3sAEd6pT8GX9lo0su6IuyFQhgA5yH+q2KsnjjHzrBtK CLr9P/MWNTm654jQZA31gBpE9XHiW80KLRwPO5eFbXQXv2dLs7MFudwdRhmz+Hs1KE XKWxpZ08z2PLw== Message-ID: <1c9b879a-7907-4849-a416-5df3db5617d6@kernel.org> Date: Wed, 25 Feb 2026 08:16:46 +0100 Precedence: bulk X-Mailing-List: kvm-ppc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [Linux PPC] Disable PREEMPT To: Christian Zigotzky , Shrikanth Hegde , linuxppc-dev , "kvm-ppc@vger.kernel.org" , Madhavan Srinivasan , Peter Zijlstra 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: fr-FR From: "Christophe Leroy (CS GROUP)" In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit +Peter Hi Christian, Le 25/02/2026 à 06:54, Christian Zigotzky a écrit : > 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? Can you give more details on why you want to be able to deactivate PREEMPT ? Read https://github.com/torvalds/linux/commit/7dadeaa6e851e > > 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 > > --- > > Thanks in advance, > > Christian >