From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from elvis.franken.de (elvis.franken.de [193.175.24.41]) by smtp.subspace.kernel.org (Postfix) with ESMTP id DCDB014E2D9; Tue, 9 Jul 2024 08:55:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.175.24.41 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720515356; cv=none; b=czrYWvoEYu30wlm9FNYCwhyntxoex8hr765WwBIkXssupByiE2KdaU2qFJjxswTHAwKsJ2wJ29Uu5eIKDt+KfixSa1JQnsYVt5SETy88XjV7XCDpeBuShXYQL7xmhsZjPs0MCx0zvkofMPU68T9F1wpHFV8bhGKYnXq0xXIgIJI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720515356; c=relaxed/simple; bh=oVjVFSnFCha3efjxmv3xh62Kiit5wNco299Vz9gRcDU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=glgJBAlTIubOzzc7MmlpERUE1n1X+4bzwXkph31wYN2XaTBN8Fnmysf3QzuDhXITm0yQvhbWakR1obJop5u0MZv3thRHxSbbYBG0hBfUXH0dIV5DYjDJxV/GL/i1DMKlsoRZr61s4KZukaxTQq9vgPQUGqqk5jRfnJRO38mLpP0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=alpha.franken.de; spf=pass smtp.mailfrom=alpha.franken.de; arc=none smtp.client-ip=193.175.24.41 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=alpha.franken.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=alpha.franken.de Received: from uucp by elvis.franken.de with local-rmail (Exim 3.36 #1) id 1sR6dK-0000Pq-00; Tue, 09 Jul 2024 10:55:34 +0200 Received: by alpha.franken.de (Postfix, from userid 1000) id C567EC0411; Tue, 9 Jul 2024 10:55:21 +0200 (CEST) Date: Tue, 9 Jul 2024 10:55:21 +0200 From: Thomas Bogendoerfer To: Jiaxun Yang Cc: "Maciej W. Rozycki" , Jonathan Corbet , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, "linux-mips@vger.kernel.org" , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= Subject: Re: [PATCH v3] MIPS: Implement ieee754 NAN2008 emulation mode Message-ID: References: <20240612-mips_ieee754_emul-v3-1-2c21b450abdb@flygoat.com> <9cc26415-9cbc-47fa-a132-7d8c000874a4@app.fastmail.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Fri, Jun 28, 2024 at 01:33:06AM +0100, Jiaxun Yang wrote: > > > 在2024年6月27日六月 下午8:54，Maciej W. Rozycki写道： > > On Thu, 27 Jun 2024, Jiaxun Yang wrote: > > > >> >> @@ -318,6 +318,10 @@ void mips_set_personality_nan(struct arch_elf_state *state) > >> >> t->thread.fpu.fcr31 = c->fpu_csr31; > >> >> switch (state->nan_2008) { > >> >> case 0: > >> >> + if (!(c->fpu_msk31 & FPU_CSR_NAN2008)) > >> >> + t->thread.fpu.fcr31 &= ~FPU_CSR_NAN2008; > >> >> + if (!(c->fpu_msk31 & FPU_CSR_ABS2008)) > >> >> + t->thread.fpu.fcr31 &= ~FPU_CSR_ABS2008; > >> > > >> > why is this needed? > >> > >> Because t->thread.fpu.fcr31 comes from c->fpu_csr31, in this case we the default > >> value of c->fpu_csr31 is read from hardware and we don't know what would that be. > > > > But it has always been like this. What has changed with your patch that > > you need to mask the bit out now? > > After this patch kernel's copy of t->thread.fpu.fcr31 can disagree with hardware. > When disagree happens, we trigger emulation. > > Before that patch for nan legacy binary running on nan2008 CPU t->thread.fpu.fcr31 > will still be nan2008 (for ieee754=relaxed) so that's not relevant. I'm considering to apply your patch, how much testing/verification did this patch see ? Do have some test binaries ? Thomas. -- Crap can work. Given enough thrust pigs will fly, but it's not necessarily a good idea. [ RFC1925, 2.3 ]