From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 55E5E201022; Thu, 6 Mar 2025 12:10:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741263007; cv=none; b=NCm+wpEddlUZNXI1v69dNv7bggbAF8tQ9yK2WdIkYbf/4KcsxlYd2/t6G5ym15Z6f8YkKQglVMXC0s85fkBqSj1TYkjOLgdgx9zS8L/l82/pbeKZiEzswc5C+Ew1cSawlgyR3TCgJ7e764sTcZuX4xBdyT4yNW3TNyU89CW374E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741263007; c=relaxed/simple; bh=4VrMJIjVFPsbDL3AXCsxRkmOwzuv5lOz64/j+1TMEco=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=PUiRFyVaNdRB/Fa5i0mFt3V8Z7x/x79LStqjZYKbhVIJXVoGviPZ8ABGqKNXgEhdQfZQ9HqES4bqOd2ohElVsRxKzuw2G4MNpLaY0JgB+iu8oUlOye2XdXbuZwGhyVVSpnJeL42TU1dlpWfvV98ZzNPXeK641S24RCjkFQMRugY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=C/ZS0pye; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="C/ZS0pye" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=JmS89W/xehVecg6LuB8zf80ZnuxBLneMU7jkajJH5Nk=; b=C/ZS0pyeW+kSZXL1yqW1XEpjHW XcCnpRcD/Bac7VesklBGS89gQoJaRAxLRjPe+TpsSJYn8z8oWWEEIo5rp3ndmFdjKleHMJSZCRfQw 3o5PIGqFwLpptvJwpzl12nrQn5tONJmxjjHxnJrj4fUnVCfLQg2ggLgfz0wRu4vSCvRY9aaLtetIa Ywp7lbl0EjQSim7K0ow06uMH6Ag3KBsFvBrfwhpcKG2ihaDgr8bHp1hYOYD90sNfVCitswjxFlrbn FEX8imaHo8Kue6UKonywD95qO30gT7wO0Qfuv7NprVgcbcRS7njmUs1qv35f3Hq+MmJaORZwzDVXp pbIW66VQ==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tqA2u-000000094eH-2HZO; Thu, 06 Mar 2025 12:09:50 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 438FD30049D; Thu, 6 Mar 2025 13:09:47 +0100 (CET) Date: Thu, 6 Mar 2025 13:09:47 +0100 From: Peter Zijlstra To: Ingo Molnar Cc: Eric Biggers , x86@kernel.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, Ard Biesheuvel , Ben Greear , Xiao Liang , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Andy Lutomirski , "Jason A . Donenfeld" Subject: Re: [RFC PATCH v2] x86/fpu: make kernel-mode FPU reliably usable in softirqs Message-ID: <20250306120947.GF16878@noisy.programming.kicks-ass.net> References: <20250304204954.3901-1-ebiggers@kernel.org> Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Mar 05, 2025 at 10:07:45AM +0100, Ingo Molnar wrote: > > From: Eric Biggers > > Alternatives considered: > > > > - Make kernel-mode FPU sections fully preemptible. This would require > > growing task_struct by another struct fpstate which is more than 2K. > > So that's something that will probably happen once the kernel is built > using APX anyway? ISTR looking into this at some point for RT. I also have vague memories of other architectures doing something similar, but its all a long time ago.