From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: Re: [PATCH 21/22] arm64: replace ZONE_DMA with ZONE_DMA32 Date: Wed, 10 Jan 2018 17:10:02 +0000 Message-ID: <3c3263ca-b0ab-654a-d67d-f5ff5e31280c@arm.com> References: <20180110080932.14157-1-hch@lst.de> <20180110080932.14157-22-hch@lst.de> <0371cef8-d980-96da-9cb5-3609c39be18a@arm.com> <20180110155517.GA18774@lst.de> <20180110155546.GB18903@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180110155546.GB18903-jcswGhMUV9g@public.gmane.org> Content-Language: en-GB List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Christoph Hellwig Cc: linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mips-6z/3iImG2C8G8FEW9MqTrA@public.gmane.org, Michal Simek , linux-ia64-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, =?UTF-8?Q?Christian_K=c3=b6nig?= , x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Konrad Rzeszutek Wilk , Guan Xuetao , linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: linux-arch.vger.kernel.org On 10/01/18 15:55, Christoph Hellwig wrote: > 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. Hee hee - cramming it into 4.15 is exactly what I wouldn't want to do, even if Linus would accept it :) Landing it this merge window for 4.16-rc1 sounds good if we can manage that. Robin. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com ([217.140.101.70]:46162 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934390AbeAJRKH (ORCPT ); Wed, 10 Jan 2018 12:10:07 -0500 Subject: Re: [PATCH 21/22] arm64: replace ZONE_DMA with ZONE_DMA32 References: <20180110080932.14157-1-hch@lst.de> <20180110080932.14157-22-hch@lst.de> <0371cef8-d980-96da-9cb5-3609c39be18a@arm.com> <20180110155517.GA18774@lst.de> <20180110155546.GB18903@lst.de> From: Robin Murphy Message-ID: <3c3263ca-b0ab-654a-d67d-f5ff5e31280c@arm.com> Date: Wed, 10 Jan 2018 17:10:02 +0000 MIME-Version: 1.0 In-Reply-To: <20180110155546.GB18903@lst.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Christoph Hellwig Cc: iommu@lists.linux-foundation.org, linux-arch@vger.kernel.org, linux-mips@linux-mips.org, Michal Simek , linux-ia64@vger.kernel.org, =?UTF-8?Q?Christian_K=c3=b6nig?= , x86@kernel.org, linux-kernel@vger.kernel.org, Konrad Rzeszutek Wilk , Guan Xuetao , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org Message-ID: <20180110171002.aDqX6Ivd2SR4xpYIWWjEg1Rmclke3rICHSJPeCSFxXU@z> On 10/01/18 15:55, Christoph Hellwig wrote: > 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. Hee hee - cramming it into 4.15 is exactly what I wouldn't want to do, even if Linus would accept it :) Landing it this merge window for 4.16-rc1 sounds good if we can manage that. Robin.