Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965904AbeAJPzu (ORCPT + 1 other); Wed, 10 Jan 2018 10:55:50 -0500 Received: from verein.lst.de ([213.95.11.211]:47831 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964902AbeAJPzr (ORCPT ); Wed, 10 Jan 2018 10:55:47 -0500 Date: Wed, 10 Jan 2018 16:55:46 +0100 From: Christoph Hellwig To: Robin Murphy Cc: Christoph Hellwig , iommu@lists.linux-foundation.org, linux-arch@vger.kernel.org, linux-mips@linux-mips.org, Michal Simek , linux-ia64@vger.kernel.org, Christian =?iso-8859-1?Q?K=F6nig?= , x86@kernel.org, linux-kernel@vger.kernel.org, Konrad Rzeszutek Wilk , Guan Xuetao , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 21/22] arm64: replace ZONE_DMA with ZONE_DMA32 Message-ID: <20180110155546.GB18903@lst.de> References: <20180110080932.14157-1-hch@lst.de> <20180110080932.14157-22-hch@lst.de> <0371cef8-d980-96da-9cb5-3609c39be18a@arm.com> <20180110155517.GA18774@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180110155517.GA18774@lst.de> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Wed, Jan 10, 2018 at 04:55:17PM +0100, Christoph Hellwig wrote: > On Wed, Jan 10, 2018 at 12:58:14PM +0000, Robin Murphy wrote: > > On 10/01/18 08:09, Christoph Hellwig wrote: > >> arm64 uses ZONE_DMA for allocations below 32-bits. These days we > >> name the zone for that ZONE_DMA32, which will allow to use the > >> dma-direct and generic swiotlb code as-is, so rename it. > > > > I do wonder if we could also "upgrade" GFP_DMA to GFP_DMA32 somehow when > > !ZONE_DMA - there are almost certainly arm64 drivers out there using a > > combination of GFP_DMA and streaming mappings which will no longer get the > > guaranteed 32-bit addresses they expect after this. I'm not sure quite how > > feasible that is, though :/ > > I can't find anything obvious in the tree. The alternative would be > to keep ZONE_DMA and set ARCH_ZONE_DMA_BITS. > > > That said, I do agree that this is an appropriate change (the legacy of > > GFP_DMA is obviously horrible), so, provided we get plenty of time to find > > and fix the fallout when it lands: > > > > Reviewed-by: Robin Murphy > > I was hoping to get this into 4.15. What would be proper time to > fix the fallout? Err, 4.16 of course.