From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay5-d.mail.gandi.net (relay5-d.mail.gandi.net [217.70.183.197]) (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 A3855288D2 for ; Mon, 1 Dec 2025 16:29:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.183.197 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764606571; cv=none; b=TpsUt4eIj0EgRNgCODd514Wnc4jqRluRKpulr2NKxN8H3L24XszKeR/BD6bovFj33hX+x3kTWxNYU6tc+VQsH5Xi/7NN3+hCV0ABGMUBmLapibtmxIbg2Seab8BhRHWS3AeLzRorSyGuM/806PLrXCjjeH0sd/R8SG0SjT1HCys= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764606571; c=relaxed/simple; bh=VMR3Tzs1Ty0WYAztjk0Rt0NwJ4j6UqG1tsxHAxKQQ58=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=jag5cH2ZLjFiKGrNPz4Ve7oDKYQCxFVgLmLKTcZC1TzLCld6/DGu6ZPfC9LEQFRaIn/tJKm+QsdwxHf+c4/v9TTupkYe7tzSz0mYd0EKNFH3Te082zuMsShMKMlPuEniQeVc+mz5/WWFNU2NAD5irAQwIg95kYDEsyJ7+WywQlw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=xenomai.org; spf=pass smtp.mailfrom=xenomai.org; dkim=pass (2048-bit key) header.d=xenomai.org header.i=@xenomai.org header.b=T+Wtm/Yq; arc=none smtp.client-ip=217.70.183.197 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=xenomai.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=xenomai.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=xenomai.org header.i=@xenomai.org header.b="T+Wtm/Yq" Received: by mail.gandi.net (Postfix) with ESMTPSA id 8F54543EE7; Mon, 1 Dec 2025 16:29:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=xenomai.org; s=gm1; t=1764606561; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=el0GMOoqfGECUSo03V4BXP77MkqUpbOZ95zu2pCHaKM=; b=T+Wtm/Yq7M3c26sEMgJFC6SU7XrSRFFktVU3LDkUXM/VNHHISWgZeAaj9udQFJnL7UabiS I1foKQED9pQsut1s4w+WczgwGvXp3FNL4+VcFsL6P/fWqDDo7JhJWd7AUfJDCHMrrAuVeL YX+necx49l/2pEoy/fI/4YlukgiUOH0el3G/ihgORgUhJFMNtm6cPJ2ETGuB2DGKRldOYg 1I9x1hZ7eTECPnEhO3KZHfD7cB4smq8Mts1MdlFBNTwRXtgIqu4J5CNJgye3Qj76VEKqYJ BrCgHEtN1dk0fT7HSSv2veb/J897YXmCa2cK8vYqpQ07JgVL5DnIKiLoSQxRYg== From: Philippe Gerum To: Florian Bezdeka Cc: xenomai@lists.linux.dev, Jan Kiszka Subject: Re: [PATCH RFC Dovetail 6.1 0/3] arm64: Enable in-kernel FPU / FPSIMD usage In-Reply-To: <20251119-flo-6-1-arm64-fpsimd-test-enablement-v1-0-8653c0b573fd@siemens.com> (Florian Bezdeka's message of "Wed, 19 Nov 2025 15:25:18 +0100") References: <20251119-flo-6-1-arm64-fpsimd-test-enablement-v1-0-8653c0b573fd@siemens.com> User-Agent: mu4e 1.12.12; emacs 30.2 Date: Mon, 01 Dec 2025 17:29:16 +0100 Message-ID: <875xaq88tf.fsf@xenomai.org> Precedence: bulk X-Mailing-List: xenomai@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-GND-State: clean X-GND-Score: -100 X-GND-Cause: gggruggvucftvghtrhhoucdtuddrgeeffedrtdeggddvheekudelucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuifetpfffkfdpucggtfgfnhhsuhgsshgtrhhisggvnecuuegrihhlohhuthemuceftddunecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpefhvfevufgjfhgffffkgggtsehttdertddtredtnecuhfhrohhmpefrhhhilhhiphhpvgcuifgvrhhumhcuoehrphhmseigvghnohhmrghirdhorhhgqeenucggtffrrghtthgvrhhnpedvlefhvdehkeduheevleegiedtueejgfekhfeijeefvdeijeekgeeigfejhfekgeenucfkphepvdgrtddumegvtdgrmedulegsmeeftggutdemleeklegrmeehtgegsgemsgejfhhfmegsrghfnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehinhgvthepvdgrtddumegvtdgrmedulegsmeeftggutdemleeklegrmeehtgegsgemsgejfhhfmegsrghfpdhhvghlohepphihrhhopdhmrghilhhfrhhomheprhhpmhesgigvnhhomhgrihdrohhrghdpnhgspghrtghpthhtohepfedprhgtphhtthhopehjrghnrdhkihhsiihkrgesshhivghmvghnshdrtghomhdprhgtphhtthhopeigvghnohhmrghisehlihhsthhsrdhlihhnuhigrdguvghvpdhrtghpthhtohepfhhlohhrihgrnhdrsggviiguvghkrgesshhivghmvghnshdrtghomh X-GND-Sasl: rpm@xenomai.org Florian Bezdeka writes: > Hi all, > > these are the necessary backports for dovetail 6.1 that would allow us to > enable the in-kernel FPU usage of switchtest. This is currently not > possible as dovetail < 6.12 does not allow / implement the necessary fpsimd > context switching. > > I have backported the necessary patches down to 5.10. That would allow > us to unconditionally enable the tests for the xenomai3-next branch. I > will send out the 5.15 and 5.10 series once we agreed that this version > (targeting 6.1) is correct. > > Please note that there is a small problem with this series. Patch 1 > removes the check/flag that was used by the dovetail enablement code to > detect in-band FPU usage. The new flag is implemented differently in > patch 2. Patch 2 also fixes the usage of that flag. I had no better > idea. Otherwise I would have to delete? the in-kernel fpu preemption > code (temporary). TIF_KERNEL_FPSTATE is not covering a preemption of a softirq handler using the NEON unit by an oob thread when PREEMPT_RT is disabled, kernel or user for that matter. i.e. It looks like this aspect was overlooked during the busy -> TIF_KERNEL_FPSTATE transition for Dovetail, so a broader fix may be required. We may have to use a marker which covers any type of preempted context. -- Philippe.