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 8F56613AA2D; Thu, 1 Aug 2024 01:24:27 +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=1722475467; cv=none; b=FfxZGOYU5XiWZn0GvJKDCCvppu2SUZu9eG+Eu4AwEOJzaIaXCo7QJ98qJlOt8HeSpcK6o6B4o6d0PHX/C1/Tduj134Hkx7kQcnzxwyLL7pupUFI2NTRuRJpBijr6B4ztngbvPxIkX3az5xvVEGbmqiqT8ycpG/4687f2+Nwp6Bs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722475467; c=relaxed/simple; bh=Pgpqo4RtxVJ1ue8DwjL2l0l2UL9ejI31ZTKHWsBrk4Q=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Dq2OwA7S1jIfir6der6dsrP8L1KAJlTfq6QP4CQ/ucCAkIGdyNRjQFrdDL11ze8csPvFx8GhHGKRDRIwHr0RnNlbohryOEbwvvmLrvEwZbdDB+sICMRjrReigMyUDo7cIfG08PjtbB5JcRzBl9SiDs3cuJE3DuVZ8qjNYtSVJO8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XVZIR7ZC; 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="XVZIR7ZC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1FD22C116B1; Thu, 1 Aug 2024 01:24:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722475467; bh=Pgpqo4RtxVJ1ue8DwjL2l0l2UL9ejI31ZTKHWsBrk4Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XVZIR7ZCGTG0w41hQSmLUNL6cZMuc0xp588STEletZW6rGg2Zw5ATIgyJNDcnVReb B3EfWzjWskItTFqdGEFqKaNkyGttT9TLBlQWyu/w8Tuxs0k3bHkwZd0cu+hd+HJiBM TLWeLNnPzjvU1idP/yzgeefl8ZzJqv2fdNIoFW2QL9yRXpPiUWdGcYIxH9/tq99yFQ xlNDkZrz9RPWiLvSDiSFXG1SG7k6RBe2KkK8hixvDn+6BA8ozx+ajPaXfsgWLA8nel 7BEThuYora+MdjBceQZNxXOF5muIGxkG3oYUZNn0HCWNcoz+pncWSlk+9RsOGJ4U29 oEus3plyggpmg== Date: Wed, 31 Jul 2024 18:24:24 -0700 From: Nathan Chancellor To: Christoph Hellwig Cc: kernel test robot , Baruch Siach , Marek Szyprowski , Catalin Marinas , Will Deacon , llvm@lists.linux.dev, oe-kbuild-all@lists.linux.dev, linux-s390@vger.kernel.org, Ramon Fried , Petr =?utf-8?B?VGVzYcWZw61r?= , Robin Murphy , linux-kernel@vger.kernel.org, iommu@lists.linux.dev, Elad Nachman , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v3 2/3] dma-mapping: replace zone_dma_bits by zone_dma_limit Message-ID: <20240801012424.GA1640480@thelio-3990X> References: <053fa4806a2c63efcde80caca473a8b670a2701c.1722249878.git.baruch@tkos.co.il> <202407300338.oaUo6jtB-lkp@intel.com> <20240730021208.GA8272@thelio-3990X> <20240730153450.GA30021@lst.de> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240730153450.GA30021@lst.de> On Tue, Jul 30, 2024 at 05:34:50PM +0200, Christoph Hellwig wrote: > On Mon, Jul 29, 2024 at 07:12:08PM -0700, Nathan Chancellor wrote: > > > | ~~~~~~~~~~~~~~ ^~~~~~~~~~~~~~~~ > > > include/linux/dma-mapping.h:77:40: note: expanded from macro 'DMA_BIT_MASK' > > > 77 | #define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1)) > > > | ^~~~~ > > > 2 warnings generated. > > > > FWIW, this is likely a false positive due to an issue in Clang with the > > control flow graph for global variables: > > > > https://github.com/ClangBuiltLinux/linux/issues/92 > > > > DMA_BIT_MASK() has been the biggest offender :/ If there is any way to > > refactor this code to avoid this, that would be great (as that has been > > one of our longest outstanding issues and getting it fixed in the > > compiler does not seem super easy at this point). > > I have no idea what you'd want changed here, but I'll happily take > patches. Unfortunately, I am not sure either... I do not see anything obviously, so perhaps it could just be avoided with the __diag() infrastructure? diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index 3dbc0b89d6fb..b58e7eb9c8f1 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -20,7 +20,12 @@ * it for entirely different regions. In that case the arch code needs to * override the variable below for dma-direct to work properly. */ +__diag_push(); +__diag_ignore(clang, 13, "-Wconstant-conversion", + "Clang incorrectly thinks the n == 64 case in DMA_BIT_MASK() can happen here," + "which would truncate with a 32-bit phys_addr_t"); phys_addr_t zone_dma_limit __ro_after_init = DMA_BIT_MASK(24); +__diag_pop(); static inline dma_addr_t phys_to_dma_direct(struct device *dev, phys_addr_t phys)