From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f198.google.com (mail-wr0-f198.google.com [209.85.128.198]) by kanga.kvack.org (Postfix) with ESMTP id 14F6F6B0005 for ; Tue, 24 Apr 2018 03:55:19 -0400 (EDT) Received: by mail-wr0-f198.google.com with SMTP id l6-v6so15231145wrn.17 for ; Tue, 24 Apr 2018 00:55:19 -0700 (PDT) Received: from newverein.lst.de (verein.lst.de. [213.95.11.211]) by mx.google.com with ESMTPS id 48-v6si11552164wru.268.2018.04.24.00.55.17 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 24 Apr 2018 00:55:17 -0700 (PDT) Date: Tue, 24 Apr 2018 09:56:45 +0200 From: Christoph Hellwig Subject: Re: [PATCH 11/12] swiotlb: move the SWIOTLB config symbol to lib/Kconfig Message-ID: <20180424075645.GA19379@lst.de> References: <20180423170419.20330-1-hch@lst.de> <20180423170419.20330-12-hch@lst.de> <20180423235205.GH16141@n2100.armlinux.org.uk> <20180424065549.GA18468@lst.de> <20180424074726.GI16141@n2100.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180424074726.GI16141@n2100.armlinux.org.uk> Sender: owner-linux-mm@kvack.org List-ID: To: Russell King - ARM Linux Cc: Christoph Hellwig , Konrad Rzeszutek Wilk , iommu@lists.linux-foundation.org, linux-mips@linux-mips.org, linux-pci@vger.kernel.org, x86@kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org, sparclinux@vger.kernel.org, linux-arm-kernel@lists.infradead.org On Tue, Apr 24, 2018 at 08:47:27AM +0100, Russell King - ARM Linux wrote: > Therefore, the default state for SWIOTLB and hence NEED_SG_DMA_LENGTH > becomes 'y' on ARM, and any defconfig file that does not mention SWIOTLB > explicitly ends up with both these enabled. Indeed, sorry. > It does look a bit weird though - patch 10 arranged stuff so that we > didn't end up with SWIOTLB always enabled, but this patch reintroduces > that with the allowance that the user can disable if so desired. I am not very happy with that patch, but I have a hard time coming up with something saner. Bascially x86_64 and mips/loongson default to SWIOTLB=y but allow to deselect it, powerpc has it optional without any real dependency and defaults to n and everyone just selects it otherwise. I suspect the right thing is to just have it always one for x86_64 and loongson and have a ppc-specific option to enable it on powerpc so that we can always use select statements. I'll do that for the next round.